Nuclei in the Cosmos XV

24 Jun 2018, 16:00 → 29 Jun 2018, 18:00 Europe/Rome

"E. Fermi" conference room (LNGS)

Alba Formicola (LNGS)

 

This is the Indico page of the 15^th International Symposium on Nuclei in the Cosmos. Official website can be found at: http://nic2018.lngs.infn.it/

The conference is the fifteenth in the Nuclei in the Cosmos (NIC) biennial series. The focus of the NIC XV conference will be the cross-fertilization of nuclear physics research with astrophysical topics.

The conference aims to address the current major achievements in nuclear physics, astrophysics, astronomy, cosmo-chemistry and neutrino physics that provide the necessary framework for any microscopic understanding of astrophysical processes, as well as for discussing the future directions and perspectives in the various fields of Nuclear Astrophysics research.

Thus the NIC XV program will consist of invited review talks and selected oral and poster contributions on important experimental and theoretical results in nuclear, particle and astrophysics researches, as well as a detailed and thorough exposition of the modern challenges in nuclear astrophysical scenarios.

In addition a limited number of talks of more general interest about Double Beta Decay, Dark Matter, will be included in the conference program to provide an overview of different aspects of underground physics.

Please refer to conference main site for all information regarding conference fee, registration, abstract submission, travel and accommodation and relevant details.
 

Abstract form abstractTemplateNIC2018.tex

Sunday, 24 June

Registration

Monday, 25 June

Registration

1 Welcome

Speakers: Fernando Ferroni (INFN President), Stefano Ragazzi (LNGS Director)

Stellar contribution: WDs, Novae SNeIa, & X-ray burst

Convener: Inmaculata Dominguez (Universidad de Granada)

2 NIR and MIR Signatures of Thermonuclear SNe: New Prospects in the Age of JWST

Thermonuclear Supernovae, so called Type Ia SNe, are one of the building blocks of modern cosmology, important of the origin of elements and laboratories for the explosion physics of White Dwarfs stars (WD) in close binary systems. Solving the discrepancy in the Hubble constant Ho between the Microwave background and the empirical SNe~Ia-based methods has direct consequences for the BigBang nucleosynthesis and its use for high precision cosmology, early Black Hole formation and testing new physics beyond the high-energy standard model. Is the difference in Ho a calibration issue or do we need a better understanding of SNe Ia? From theory, the empirical SNe~Ia relation for cosmology are stable because basic nuclear physics determines the progenitor structure, the explosion physics, average expansion velocities, leading to similar light curve shapes and spectral evolution for a diversity of progenitor systems and explosion scenarios with different masses M but similar M(56Ni)/M(WD) ratios and, thus, different Hubble constants. In this talk, I will give an overview how recent advances in theoretical modeling, discuss new physical effects commonly neglected and discuss observational constraints in the age of time-domain and multi-wavelength astronomy for progenitor and explosion models which show emerging links and future prospects with ground upcoming ground based, ELT, GMT and space based such as JWST, Euclide and WFIRST instruments.

Speaker: Peter Hoeflich (University of Florida)

Abstract ID_127_Hoeflich.pdf

Slides Hoeflich_NIC2018_public_version.pdf

3 "12321" Models of Classical Nova Explosions

Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in stellar binary systems. The material piles up under degenerate conditions, driving a thermonuclear runaway. The energy released by the suite of nuclear processes operating at the envelope heats the material up to peak temperatures of (100 - 400) MK. During these events, about 10-3 - 10-7 solar masses, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, Al) are ejected into the interstellar medium. In this talk, we present new multidimensional simulations of mixing at the core-envelope interface during classical novae, for different masses and chemical compositions of the underlying white dwarf. Accretion of solar composition material onto CO and ONe white dwarfs was initially computed with the 1D hydrodynamic code SHIVA. When the temperature at the core-envelope interface reached 100 MK, the structure was mapped onto a 3D cartesian grid that was subsequently followed with the multidimensional code FLASH ("1 to 3" or "123" models). In this multidimensional framework, Kelvin-Helmholtz instabilities can naturally lead to self-enrichment of the accreted envelope with material from the underlying white dwarf at levels that agree with observations.The final fate of the runaway was followed with SHIVA, remapping the 3D structure onto a 1D grid ("3 to 1" or "321" models), which allows the investigation of the dynamic stages of the explosion. New nucleosynthesis results, with particular emphasis on the production of 7Li, recently reported from observations of novae, will also be presented.

Speaker: Jordi Jose (UPC Barcelona)

Abstract 149_Jose.pdf

4 Constraining type I X-ray burst models

Type I X-ray bursts are powerful thermonuclear explosions ignited in the envelope of accreting neutron stars. Fast (p,gamma) and (alpha,p) reactions quickly drive the reaction flow towards the proton dripline before decaying back via slow beta^+ and EC decays. Since the energy generation is mainly driven by nuclear reactions and decays, type I X-ray burst models still suffer from uncertain reaction rates. Recently, it has been shown that only a few single reactions contribute significantly to the overall uncertainty in the modelling of the main observable of this event: the X-ray luminosity light curve. In order to extract astrophysical parameters of the neutron star, however, uncertainties in the light curve modelling urgently need to be minimized. Since many of the important reactions are located at or close to the proton dripline, measurements are very challenging and require complicated setups utilizing radioactive ion facilities. In almost all cases, it is impossible to measure the desired reaction directly. To overcome this problem, new techniques and upgraded setups are combined giving access to reaction studies so far unreachable. In this contribution, some selected recent reaction and mass measurements for the rp process will be presented. Updated results on the important Al(p,gamma)Si reaction will be shown utilizing a new measurement technique. Also, some open remaining questions will be discussed.

Speaker: Christoph Langer (University of Frankfurt)

Abstract 78_Langer.pdf

5 Heavy Elements Nucleosynthesis On Accreting White Dwarfs surface: seeding the the p-process

The production of the proton-rich isotopes beyond iron that we observe today in the solar system is still uncertain. Thermonuclear supernovae (SNe Ia) exploding within the single-degenerate scenario have been proposed to be a potential source for these isotopes. Recent works studying the p -process production in SNe Ia assume s -process rich pre-explosive seeds, built by neutron captures in the external layers of the progenitor, during the accretion phase. Presently there are no complete stellar models calculating these abudances, covering the WD mass range up to the Chandrasekhar mass. We calculate accretion models for five white dwarfs (WDs) with different initial masses (0.85, 1, 1.26, 1.32, 1.38 solar masses) using the stellar code MESA. We then focus on the nucleosynthesis of the 1, 1.26, 1.32 and 1.38 solar masses models, calculating the full abundance distribution. In our models the dominant neutron source are the 22Ne(α,n)25Mg, which is activated at the bottom of the convective thermal pulse driven by the He flashes along the accretion phase, for WD masses lower than 1.26 solar masses, and the 13C( α ,n)16O for WD masses equal or higher than 1.26 solar masses. We found neutron densities up to few 10^15 cm^−3 in the most massive WDs. In particular, the neutron density and the total production of neutrons increase with increasing mass of the accreting WD. The abundance distribution peaks between Fe and Zr for the models at M = 0.85 and 1 solar masses, while for larger WDs much higher production efficiency is obtained beyond iron, with a strong production up to the Pb region. Using these results, we compute the nucleosynthesis of proton rich heavy isotopes using a multi-D SNe Ia model, and discuss the uncertainties affecting our results. Finally, the frequency of the single-degenerate scenario channel to produce SNIa is controversial. The impact on the p-process production in this scenario is also discussed.

Speaker: Umberto Battino (University of Edinburgh)

Abstract 79_Battino.pdf

Slides Battino_NIC2018_public_version.pdf

11:15 Coffee break

Carbon fusion

Convener: Frank Strieder (South Dakota School of Mines & Technology)

6 The resonant behaviour of the 12C + 12C fusion cross section at astrophysical energies

Speaker: Aurora Tumino (Kore University & INFN)

Abstract Tumino.pdf

7 Mup and the 12C+12C reaction rate, an update

Mup is the minimum mass of a star that, after the core-helium burning, develops temperature and density conditions for the occurrence of a hydrostatic carbon burning. Stars whose mass is lower than this limit are the progenitors of C-O white dwarfs and, when belong to a close binary system, may give rise to explosive phenomena, such as cataclysm variables, novae or type Ia supernovae. Stars whose mass is only slightly larger than Mup ignite C in a degenerate core and, in turn, experience a thermonuclear runaway. Their final destiny may be either a massive O-Ne white dwarf or an e-capture supernova. More massive objects ignite C in non-degenerate conditions and they are are the progenitors of various type of core-collapse supernovae (IIp. IIL, IIN, Ib, Ic). In spite of its importance, a precise evaluation of Mup is still missing. It relies on our knowledge of various input physics used in stellar modelling, such as the plasma neutrino rate, responsible of the cooling of the core, the equation of state of high density plasma, which affects the compressibility and the consequent heating of the core, and the 12C+12C reaction rate. In addition Mup depends on the Initial Mass-Core Mass relation, which is determined by the extension of the convective instabilities during the H and He-burning phases (convective overshoot, semiconvection, rotational induced instabilities). Stimulated by recent results of new experimental investigations on the 12C+12C reaction, we will present in this talk an update of the Mup calculation.

Speakers: Aurora Tumino (University Kore), Inmaculata Dominguez (University of Granada), Luciano Piersanti (INAF - OAA), Oscar Straniero (INAF - OAA)

Abstract 99-Straniero.pdf

8 Characterizing the astrophysical S-factor for 12C + 12C with wave-packet dynamics

A quantitative study of the astrophysically important sub-barrier fusion of 12C + 12C will be presented [1]. Low-energy collisions are described in the body-fixed reference frame using wave-packet dynamics within a nuclear molecular picture. A collective Hamiltonian drives the time propagation of the wave-packet through the collective potential-energy landscape. The fusion imaginary potential for specific dinuclear configurations is crucial for understanding the appearance of resonances in the fusion cross section. In contrast to other commonly used methods, such as the potential model and the conventional coupled-channels approach, these new calculations reveal three resonant structures in the S-factor, as shown in Fig. 1. The structures correlate with similar structures in the data. The structures in the data that are not explained are possibly due to cluster effects in the nuclear molecule, which are to be included in the new approach. [1] A. Diaz-Torres and M. Wiescher, 2018, arXiv: 1802.01160 [nucl-th].

Speaker: Alexis Diaz-Torres (University of Surrey)

Abstract 1_Diaz-Torres.pdf

Slides Diaz-Torres_NIC2018_public_version.pdf

9 The carbon fusion reaction at stellar energies

The carbon fusion reaction is a crucial reaction in stellar evolution. Due to its complicated reaction mechanism, there is a large uncertainty in the reaction rate which limits our understanding to various stellar objects, such as massive stars, type Ia supernovae, and superbursts. In this talk, I will review the challenges in the study of carbon burning. I will also report recent results from our studies: 1) an upper limit for the 12C +12C fusion cross sections; 2) examination of the predictive power of extrapolating models for the carbon fusion reaction at stellar energies. An outlook for the future studies will also be presented.

Speaker: Xiaodong Tang (Institute of Modern Physics, CAS)

Abstract ID_137_Tang.pdf

13:00 Lunch

Cosmology and big bang nucleosynthesis

Convener: Shigeru Kubono (RIKEN Nishina Center)

10 Data for S process from n TOF

The neutron time-of-flight facility n TOF is operating at CERN since 2001. It consists of two beam lines, located at 185 and 19 m from the neutron-producing target. The main features of the neutron beam are the wide range of neutron energies, spanning over more than 10 orders of magnitude from the meV to the GeV region, the high instantaneous neutron flux and the high resolution on the neutron energy. So far, a considerable amount of important (n, g) reactions for nuclear astrophysics have been studied. In particular the n TOF collaboration has carried out a dedicated program of neutron capture measurements, which aims at determining and improving cross sections for a number of isotopes relevant to S-process nucleosynthesis: (i) for the radioactive branch-point isotopes (e. g. 151Sm [1], 63Ni [2], 147Pm, 171Tm and 204Tl); (ii) for the Pb isotopes and 209Bi, important for the situation at the termination point of the S process path; (iii) for stable isotopes with small capture cross sections (e. g. 139La [3] and various Zr isotopes [4]), which act as bottlenecks in the S-process reaction flow; (iv) for the Mg isotopes [5, 6], which represent a neutron poison and give important constraints for the 22Ne(, n) neutron source; (v) for S-only isotopes such as 154Gd, which can be produced only via S process because they are shielded against the -decay chains from the R-process region by stable isobars; (vi) for the Os isotopes [7], which are a crucial input for the Re/Os cosmo-chronometer. The present astrophysical program is concentrating on measurements of Ge, Zn, Se, as well as Y, Sr and Ce isotopes. After a brief review of the characteristics of the facility, a summary of the most important results obtained so far, and an outlook on the future astrophysical program will be presented. References [1] U. Abbondanno, et al., (The n TOF Collaboration), Phys. Rev. Lett. 93, 161103 (2004). [2] C. Lederer, et al., (The n TOF Collaboration), Phys. Rev. Lett. 110, 022501 (2013). [3] R. Terlizzi, et al., (The n TOF Collaboration), Phys. Rev. C 75, 035807 (2007). [4] G. Tagliente, et al., (The n TOF Collaboration), Phys. Rev. C 87, 014622 (2013). [5] C. Massimi, et al., (The n TOF Collaboration), Phys. Rev. C 85, 044615 (2012) [6] C. Massimi, et al., (The n TOF Collaboration), Phys. Lett. B 768, 1 (2017) [7] K. Fujii, et al., (The n TOF Collaboration), Phys. Rev. C 82, 015804 (2010)

Speaker: Cristian Massimi (University of Bologna & INFN)

Abstract ID_034_Massimi.pdf

Slides Massimi_NIC2018_public_version.pdf

11 Cross sections of 7Be+d measured at low energies and implications for Big-Bang nucleosynthesis

The cross sections of nuclear reactions between the radioactive isotope 7Be and deuterium, a possible path of reducing the production of mass-7 nuclides in Big-Bang nucleosynthesis, were measured at center-of-mass energies between 0.2 MeV and 1.5 MeV. The experiment was performed with the ANASEN active-target detector system at the RESOLUT facility of Florida State University. We measured cross sections consistent with prior measurements at higher energies but significantly higher yields at lower energy and inside the Gamow window. The implications for the primordial lithium problem will be discussed.

Speaker: Ingo Wiedenhoever (Florida State University)

Abstract 128_Wiedenhoever.pdf

12 A new measurement of the 2H(p,gamma)3He cross section in the BBN energy range at LUNA

The abundances of the primordial elements are sensitive to the physics of the early universe and are therefore a tool to test the Standard Cosmological Model. The Big Bang Nucleosynthesis (BBN) theory is one of the pillars of standard cosmology: for a given baryon density it provides the abundance of the primordial elements. Interestingly the abundance of deuterium deduced from observation of pristine gas at high redshift is more accurate with respect to the computed value [1, 2], mainly because the BBN calculation is affected by the paucity of data for the deuterium burning reaction 2H(p,γ)3He cross section at the relevant energies [3]. The concern for the 2H(p, γ)3He cross section error is made worse by the fact that the theoretical and experimental values do not agree at the level of 20% [3, 4, 5]. A new measurement with a 3% accuracy would be very important to push down the BBN uncertainty on deuterium abundance to the same level of observations. Deep underground in the Gran Sasso laboratory, Italy, the LUNA collaboration is pursuing a dedicated effort to measure the 2H(p, γ)3He cross section directly at BBN energies (30 -300 keV). The campaign, started in 2016, is divided into two phases based on a BGO and a high-purity germanium (HPGe) detector, respectively. In the present talk the LUNA measurement is described and results from both phases are discussed. The impact of this measurement in cosmology and particle physics is also highlighted: a precision measurement would allow to provide an independent cross-check of the determination of the universal baryon density Ωb from the cosmic microwave background and to constrain the existence of the so called dark radiation. References [1] R.J. Cooke, M. Pettini and C.C. Steidel, Astrophysical Journal 855 (2018) 102 [2] O. Pisanti et al., Comput. Phys. Commun. 178 (2008) 956. [3] L. Ma et al., Phys. Rev. C 55 (1997) 558. [4] L.E. Marcucci et al., Phys. Rev. Lett. 116 (2016) 102501. [5] E.G. Adelberger et al., Rev. Mod. Phys. 83 (2011) 195.

Speaker: Sandra Maria Zavatarelli (INFN Genova)

Abstract 183_Zavatarelli.pdf

13 Few-Nucleon Reactions of Astrophysical Interest: a Review

We present a review of theoretical studies of few-nucleon reactions of astrophysical interest. In particular, we will consider, in the energy range of interest for Big Bang Nucleosynthesis (BBN), the d(p,\gamma)3He, the 4He(d,\gamma)6Li, and the 6Li(p,\gamma)7Be radiative captures. The first reaction has been studied within an ab-initio approach [1]: by using a realistic phenomenological model for the nuclear interaction and current, the astrophysical S-factor and differential cross section have been studied in a wide energy range. We will review also the consequences for the standard BBN predictions of the primordial deuterium abundance. The improvements for this study will be discussed. The theoretical predictions for the other two radiative reactions have been obtained within a phenomenological two-body framework, where the incoming nuclei are considered point-like and they are the constituents of the final bound state [2,3]. Also for these reactions, we will discuss the present status as well as the possible improvements for their theoretical predictions. References [1] L.E. Marcucci, G. Mangano, A. Kievsky, and M. Viviani, Phys. Rev. Lett. 116, 102501 (2016); Erratum: Phys. Rev. Lett. 117, 049901 (2016). [2] A. Grassi, G. Mangano, L.E. Marcucci, and O. Pisanti, Phys. Rev. C 96, 045807 (2017). [3] A. Gnech and L.E. Marcucci, in preparation.

Speaker: Laura Elisa Marcucci (Pisa University)

Abstract 26_Marcucci.pdf

Slides Marcucci_NIC2018_public_version.pdf

14 The study of 6Li(p, g)7Be reaction at LUNA

The 6Li(p, g)7Be reaction is involved in several astrophysical scenarios such as the Big Bang Nucleosynthesis, $^{6}$Li destruction in pre-main and in main sequence stars and solar neutrino production. A recent direct measurement of the 6$Li(p,gamma)7Be cross section found a resonance-like structure at E$_c.m.$=195 keV, corresponding to a E$_{x}\sim\,$5800 keV excited state in 7Be. This result has not been confirmed neither by other direct measurements nor by theoretical calculations {Barker, Ar, Prior, Dong} In order to clarify the existence of this resonance a new experiment was performed at the Laboratory for Underground Nuclear Astrophysics (LUNA), located under 1400 m of dolomite rocks of Gran Sasso. Thanks to the extremely low background environment the 6Li(p,gamma)7Be cross section can be measured down to low energies with unprecedented sensitivity. The high intensity proton beam from the LUNA400kV accelerator was delivered to 6Li evaporated targets of different composition and thickness. To detect the gamma rays from the 6Li(p,gamma)7Be a HPGe detector was mounted in close geometry. A silicon detector was also used in order to have a simultaneous detection of charged particles from the 6Li(p,alpha)3He channel. Target characterization was performed at the Helmholtz Zentrum Dresden Rossendorf in Dresden using two independent Ion Beam Analysis techniques: Nuclear Reaction Analysis and Elastic Recoil Detection Analysis. The talk will provide a detailed description of the experimental setup. In addition preliminary results will be reported. References J.J. He {et al.}, Phys. Lett. B {\bf 725} (2013) 287-291. F.C. Barker, Aust. J. Phys. {bf 33} (1980) 159 K. Arai, et al., Nucl. Phys. A {bf 699} (2002) 963. R.M. Prior, et al., Phys. Rev. C {bf 70} (2004) 055801 G.X. Dong {\it et al.}, J. Phys. G {bf 44} (2017) 045201.

Speaker: Denise Piatti (INFN Padova)

Abstract 173_Piatti.pdf

Slides Piatti_NIC2018_public_version.pdf

15 Non-extensive solution to the cosmological lithium problem

The disagreement of the predicted abundance of primordial 7Li with the observed abundance is a longstanding problem in Big Bang Nucleosynthesis theory[1, 2]. Solutions to this problem using conventional astrophysics and nuclear physics have not been successful over the past few decades[3]. We have investigated the impact on BBN predictions of adopting a generalized distribution called Tsallis distribution to describe the velocities of nucleons. We 1nd excellent agreement between predicted and observed primordial abundances of D, 4He, and 7Li for 1.069q1.082, suggesting a possible new solution to the cosmological lithium problem[4].

Speaker: Suqing Hou (Institute of Modern Physics, CAS)

Abstract 138_Hou.pdf

16:15 Coffee break

Techniques, tools and facilities for nuclear astrophysics

Convener: Zsolt Fulop (ATOMKI)

16 Nuclear Astrophysics Underground: Status & Future

Even more than 60 years after the groundbreaking publication by Burbidge, Burbidge, Fowler, and Hoyle, Nuclear Astrophysics is still a thriving and exciting research field at the interface of nuclear physics, astro¬physics, and particle physics. An important current topic is associated with the evolution of stars and its impact on the production of heavy elements. The most critical reactions are 12C(alpha,gamma)16O, 13C(alpha,n)16O, 22Ne(alpha,n)25Mg as well as 12C+12C fusion but other (p,gamma), (alpha,gamma), or (alpha,n) reactions may also play a role depending on the stellar environment. The study of these reactions at stellar energies has been a major goal by the community, in Europe, the US and increasingly also in China. However, the large cosmic ray induced background has been prohibitive for advancing these measurements into the stellar energy range and the present reaction rates rely on theoretical extrapolations that carry high uncertainties. Accelerator laboratories, located deep underground offer unique conditions for measuring these reactions at low energies as demonstrated by the success of the LUNA facility at Gran Sasso, Italy. Luna showed for the case of hydrogen burning reactions that many of these kinds of extrapolations can be significantly improved. Over the past years the CASPAR (Compact Accelerator System for Performing Astrophysical Research) laboratory has been constructed and commissioned at the Sanford Underground Research Facility (SURF) at former Homestake Gold mine (Lead, South Dakota, USA) to address the further need for such facilities. CASPAR operates a 1MV, high intensity, fully refurbished Van de Graaff accelerator that can provide beam intensities of more than hundred micro-Ampere. Furthermore, the LUNA-MV facility in Gran Sasso and as well as the JUNA project in China’s Jinping Underground Laboratory will be operational in the near future. Successful implementation of a science program at these facilities will offer great opportunities for significant progress in the field. The programs and the current status of the upcoming and existing underground accelerator facilities for Nuclear Astrophysics will be reviewed.

Speaker: Frank Strieder (South Dakota School of Mines & Technology)

Abstract ID_144_Strieder.pdf

Slides Strieder_NIC2018_public_version.pdf

17 Nuclear Reaction of Astrophysical Interest with LUNA projects

About 25 year ago LUNA (laboratory for Underground Nuclear Astrophysics) opened the era of underground nuclear astrophysics installing a home-made 50 kV ion accelerator under the Gran Sasso mountain. A second machine, with a terminal voltage of 400 kV, was then installed and it is still in operation. Most of the processes so far investigated were connected to the physics of solar neutrinos and hence to the hydrogen burning phase in stars. The interest to next and warmers stages of star evolution (i.e. helium and carbon burning) pushed a new project based on a ion accelerator in the MV range called LUNA-MV. Thanks to a special grant of the Italian Ministry of Research (MIUR), INFN is now building, inside one of the major hall at Gran Sasso, a new facility which will host a 3.5 MV single-ended accelerator able to deliver proton, helium and carbon beams with intensity in the mA range. The scientific program for the first phase of the LUNA-MV life will be described with the first experiment scheduled for June 2019.

Speaker: Paolo Prati (Genova University & INFN)

Abstract ID_68_Prati.pdf

18 Measurement of the 7Be(p, gamma)8B cross section with the recoil separator ERNA

7Be(p,gamma)8B still represents one of the major uncertainties on the predicted high energy component of solar neutrino 2ux and it has also a direct impact on the 7Li abundance after the Big Bang Nucleosynthesis. So far, experiments producing data with useful precision were performed in direct kinematics, using an intense proton beam on a radioactive 7Be target. The complicated target stoichiometry and the deterioration under beam bombardment might possibly be the origin of the discrepancies observed between the results of different measurements. Inverse kinematics, i.e. a 7Be ion beam and a hydrogen target, can shed light on systematic effects. We report here on an experiment exploiting a high intensity 7Be beam in combination with a windowless gas target and the recoil mass separator ERNA (European Recoil mass separator for Nuclear Astrophysics) at CIRCE (Center for Isotopic Research on Cultural and Environmental heritage), Caserta, Italy. Measurements in the energy range Ecm=350 to 850 keV are presented and their impact on the determination of the stellar rate of7Be(p,gamma)8B is discussed.

Speaker: Raffaele Buompane (University of Campania)

Abstract 134_Buompane.pdf

Slides Buompane_NIC_2018_public_version.pdf

19 Investigation of neutron-induced reaction at the Goethe University Frankfurt

Neutron-induced reactions are relevant for many astrophysical scenarios. The involved isotopes can be stable as during the s-process or radioactive as during the p-, i- or r-process. The different scenarios are characterized by different temperatures and neutron densities. Direct measurements of the relevant cross section are therefore ideally performed for many different energies. The most general method is the time-of-flight method, which typically requires large samples of isotopically enriched material, intense neutron sources and sophisticated detectors. The activation method alleviates many of these costly requirements at the cost of integral measurements. The Van de Graaff accelerator at the Goethe University Frankfurt provides unpulsed proton beams of up to 20 microA in the energy regime between 1.5 and 2.5 MeV. This is ideally suited for the production of neutrons via the 7Li(p,n) reaction. Many different energy spectra can be produced depending on the proton energy, the thickness of the lithium layer and the position of the irradiated sample. I will present first results and plans for future neutron activation measurements at the Goethe University Frankfurt.

Speaker: Rene Reifarth (Goethe University Frankfurt)

Abstract 119_Reifarth.pdf

20 Direct 13C(α, n)16O cross section measurement at low energies

The reaction 13C(α,n)16O is the main neutron source in the “s process”, which is responsible for the production of about half of the heavy elements in the universe. It operates in thermally pulsing low mass AGB stars at temperatures of about 90 MK. This translates to a Gamow window between ≈ 140 - 230 keV, far below the Coulomb barrier. Various measurements of the low energy cross section of 13C(α,n)16O have been performed in the past, and while remarkable results have been achieved, ultimately they environmental background on the surface of the earth has been a limiting factor. The LUNA collaboration is currently performing a measurement of 13C(α, n)16O in the low-background environment of the LNGS, where the environmental neutron flux is reduced by over three magnitudes with respect to the surface. This unique location, together with a high-efficiency low background detector and state of the art electronics that allow suppression of the intrinsic background, has already enabled us to push the low-energy cross section limit beyond what has been reached before. I will present the current status of the experiment, the plans for an upcoming next measurement campaign and preliminary results.

Speaker: Andreas Best (Federico II University of Naples & INFN)

21 Underground nuclear astrophysics experiment in Jinping China: JUNA

Jinping Underground experiment for Nuclear Astrophysics (JUNA) [1] will take the advantage of the ultra-low background of China Jinping Laboratory (CJPL) (rock depth 2400 m) and high current accelerator based on an ECR source and a highly sensitive detector to directly study a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of 25Mg(p,γ )26 Al, 19 F(p,α)16 O [2], 13C(α,n)16 O and 12 C(α,γ)16O reactions near Gamow energy. The experimental setup, which includes an accelerator system (400 kV with ECR source) with high stability and high intensity (10 emA for proton (commissioned), 2.5 emA for 4 He2+(under development), a detector system, and a shielding material with low background, will be established during the above research. The high efficiency detector system is composed of gamma (HPGe and BGO, all commissioned), neutron (3He and liquid scintillator, commissioned) and charged particle arrays. The high-power target is under development. See figure below. The main parts of accelerator system and detector arrays are ready and will be tested on ground and installed underground in 2019. Some test experiment on base level, such as 19 F(p,α)16 O, as well as detector background measurement in CJPL, were performed in ground and underground bases. One of four experiments will be started in 2019 and the first batch of four experimental results will be released in 2021. In this talk, the current progress of JUNA will be given. References [1] W. P. Liu et al., Science China 59(2016)642011. [2] J. J. He et al., Science China 59(2016)652011.

Speaker: Weiping Liu (China Institute of Atomic Energy)

Abstract 203_Liu.pdf

Welcome party

22 Bus to hotels

Tuesday, 26 June

Stellar contribution: low and intermediate mass stars

Convener: Maurizio Busso (INFN Perugia)

23 Observational constraints on nucleosynthesis from AGB and post-AGB stars in our Galaxy and its satellites

The chemical analysis of the envelopes of AGB and post-AGB stars provide a valuable tool to study the late phases of the evolution of low and intermediate mass stars. Depending on stellar mass and metallicity the resulting abundance patterns exhibit characteristic features, which provide information on the nucleosynthesis processes occurring in the interior of these stars, and on their role in the chemical evolution of galaxies. Recent progress in abundance determinations of a number of elements (e.g. Li, CNO isotopes, F, and s-elements) in AGB, post-AGB stars belonging to our Galaxy and the Local Group is reviewed. The constraints that these observations put to stellar and nucleosynthesis models are also brie2y discussed.

Speaker: Carlos Abia (Universidad de Granada)

Abstract ID_024_Abia.pdf

Slides Abia_NIC2018_public_version.pdf

24 The importance of the 13C(a,n)16O reaction in Asymptotic Giant Branch stars

Low mass Asymptotic Giant Branch stars are among the most important polluters of the interstellar medium. In their interiors, the main component (A>90) of the slow neutron capture process (the s-process) is synthesized, the most important neutron source being the 13C(a,n)16O reaction. I will present a theoretical sensitivity study (with variation up to a factor of two with respect to a reference case), carried out with the FUNS evolutionary stellar code. Variations of the 13C(a,n)16O rate do not appreciably affect s-process distributions for masses above 3 Msun at any metallicity. Apart from a few isotopes, in fact, the differences are always below 5%. The situation is completely different if some 13C burns in a convective environment: this occurs in FUNS models with M<3 Msun at solar-like metallicities. In this case, a change of the 13C(a,n)16O reaction rate leads to non-negligible variations of the elements surface distribution (10% on average), with larger peaks for some elements (as rubidium) and for neutron-rich isotopes (as 86Kr and 96Zr). Larger variations are found in low-mass low-metallicity models, if protons are mixed and burnt at very high temperatures. In this case, the surface abundances of the heavier elements may vary by more than a factor 50.

Speaker: Sergio Cristallo (INAF - OAA)

Abstract 059_Cristallo.pdf

Slides Cristallo_NIC2018_public_version.pdf

25 The i-process in super asymptotic giant branch stars

Super asymptotic giant branch (super-AGB) stars reside in the mass range approx 6-12 Msun and bridge the divide between low/intermediate-mass and massive stars. They are characterised by off-centre carbon ignition prior to a thermally pulsing phase which can consist of many 10-1000s of thermal pulses. Super-AGB stars undergo a variety of nucleosynthetic processes including proton-capture reactions at the base of the convective envelope and heavy element (s-process) production during the thermal pulses. The most massive super-AGB stars can also undergo a dredge-out event, whereby a convective helium burning region merges with an inward moving convective envelope. When these zones meet, hydrogen is mixed down to very high temperature regions where a 13C rich region forms, leading to subsequent neutron release and heavy element (i-process) production. Here we present the first detailed heavy element nucleosynthesis for dredge-out events and discuss how these results could lead to a refining of the mass boundary between high-mass and low-mass stars which has important implications for both the chemical enrichment and energetics of galaxies.

Speaker: Carolyn Doherty (Konkoly Observatory)

Abstract 185_Doherty.pdf

Slides NIC2018CarolynDoherty.pdf

26 s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

In the past years the observational evidence that s-process elements from Sr to Pb are produced by stars ascending the so-called Asymptotic Giant Branch (or ‘‘AGB”) could not be explained by self-consistent models, forcing researchers to extensive parameterizations. The crucial point is to understand how protons can be injected from the envelope into the He-rich layers, yielding the formation of 13C and then the activation of the 13C(a,n)16O reaction. Only recently, attempts to solve this problem started to consider quantitatively physically-based mixing mechanisms. Among them, MHD processes in the plasma were suggested to yield mass transport through magnetic buoyancy. In this framework, we compare results of nucleosynthesis models for low mass AGB stars (M<3Mo), developed from the MHD scenario, with the record of isotopic abundance ratios of s-elements in presolar SiC grains, which were shown to offer precise constraints on the 13C reservoir. We find that n-captures driven by magnetically-induced mixing can well account for the SiC data and that this is due to the fact that our 13C distribution fulfils the above constraints rather accurately. We show comparisons between model predictions and measurements for isotopes of Sr, Zr and Ba as representative examples of light and heavy s-elements.

Speaker: Sara Palmerini (INFN Perugia)

Abstract 032_Palmerini.pdf

Slides NIC2018-palmerini.pdf

27 The evolution of CNO isotope ratios: a litmus test for stellar IMF variations in galaxies across cosmic time

Determining the shape of the stellar initial mass function (IMF), and whether it is constant or varies in a range of environments, is the Holy Grail of modern astrophysics, because of its profound implications for the theories of stars and galaxy formation. On a theoretical ground, it is expected that the extreme conditions for star formation encountered in the most powerful starburst events in the Universe near and far favour the formation of massive stars. Direct methods of IMF determination, however, cannot probe such systems, because of the severe dust obscuration affecting the UV stellar light. The next best option is to observe CNO bearing molecules in the interstellar medium at millimetre/submillimetre wavelengths, which, in principle, provides the best indirect evidence for IMF variations. In this contribution, we present our recent findings on this issue. First, we reassess the relative roles of massive stars, asymptotic giant branch stars, and novae in the production of the rare isotopes 13C, 15N, 17O, and 18O, along with the more abundant 12C, 14N, and 16O. Then, we calibrate a proprietary chemical evolution code using Milky Way data from the literature, and extend it to discuss extragalactic data. We show that, though significant uncertainties still hamper our knowledge of the evolution of CNO isotopes in galaxies, compelling evidence for a IMF skewed towards high-mass stars can be found for galaxy-wide starbursts. In particular, we analyse a sample of submillimetre galaxies observed by us with the Atacama Large Millimetre Array at the peak of the star formation activity of the Universe. We underline that, in order to draw firm conclusions, one has to carefully select those CNO isotope ratios that are more sensitive to possible IMF variations, and less affected by observational uncertainties. At the end, ongoing and future developments of our work are briefly outlined.

Speaker: Donatella Romano (INAF, Astrophysics and Space Science Observatory, Bologna)

Abstract 33_RomanoDonatella.pdf

Slides Romano_NIC2018_public_version.pptx

10:30 Coffee break

Techniques, tools and facilities for nuclear astrophysics

Convener: Weiping Liu (China Institute of Atomic Energy)

28 Experiments using Recoil Separators

Radiative capture reactions are of paramount importance in virtually every astrophysical environment, many of them involving short-lived radionuclides away from stability. Recoil separators were adapted in order to solve the problem of those hitherto infeasible measurements where the radionuclides of interest are too short-lived to make a target onto which light projectiles could impinge. With ISOL and fragmentation facilities producing accelerated radioactive ion beams of relatively high intensity, the inverse kinematics technique of recoil separators, using hydrogen and helium targets, was a solution that conferred many additional advantages to traditional measurements, such as different, controlled sources of systematic error, and most importantly, intrinsic and substantial background suppression. However, the method poses many additional challenges also. The field of Recoil Separators using radioactive beams has become mature, with many of the challenges arising from the vastly varying experimental conditions for each reaction having now been probed in pioneering measurements. The state of the art is such that current and future recoil separators can draw upon a wide variety of techniques, data and example measurements to perform careful measurements of radiative capture reactions of astrophysical interest. Focusing on the catalogue of results and experiences from the DRAGON facility, I will discuss the performance characteristics, limitations and successes of recoil separators, highlighting reactions of importance in light of their connection to astronomical observables.

Speaker: Chris Ruiz (TRIUMF)

Abstract ID_167_Ruiz.pdf

Slides Ruiz_NIC2018_public_version.pptx

29 Data Evaluation and Extrapolation using R-matrix

Nearly all stable nuclei reactions have at least a single measurement, and many that are critically important for the modeling of energy generation and nucleosynthesis have been studied several times. This wealth of data is both a blessing and a curse. On the one hand, by combining the results of many different measurements, which have been made in independent ways, one can hope that systematic uncertainties can be drastically reduced. This works well in cases where measurements agree. However, if one 1nds that the different measurements are in disagreement, this leads to quite a mess. For reaction cross sections that fall into the category of the resolved resonance region, a very useful tool is phenomenological R-matrix [1]. It has been commonly applied over a wide range of nuclear physics. The reaction framework contains some powerful physical constraints, but does not contain much information on the underlying nuclear physics. Instead, individual levels are added to the calculation based on the resonances that are observed in the experimental data. One very useful aspect of R-matrix is that it provides a very useful framework that greatly facilitates the comparison of different sets. A good example would be two sets of differential cross section measurements that were measured at different angles. A long standing problem for R-matrix analyses, is that a standard parameter convention has never been completely established. This has lead to much confusion, since key information needed to reproduce R-matrix results has often been omitted from publications. The lack of standardization has made this vary valuable analysis tool hard to access and has lead to unnecessary confusion. In this talk I will report on a new effort by the International Atomic Energy Agency to establish a set of conventions for R-matrix evaluations of charged particle induced reactions and uncertainty estimation [2]. A consultant group has been formed, drawing on R-matrix practitioners with different backgrounds from a wide range of applications. The group is now engaged in a series of benchmarking calculations for different R-matrix codes. Once complete, guidelines will be established for R-matrix analyses that will greatly facilitate the communication of R-matrix results across multiple disciplines and establish evaluation methodology standards. Research supported by NSF PHY-1430152, and JINA PHY-1419765. References [1] Lane and Thomas, Rev. Mod Phys. 30 (1958) 257. [2] Leeb, Dimitriou, and Thompson, INDC(NDS)-0726 (2016)

Speaker: Richard deBoer (University of Notre Dame)

Abstract ID010_deBoer.pdf

Slides deBoer_NIC2018_public_version.pdf

30 Fluorine nucleosynthesis: measurement of 15N(α,γ)19F

The origin of fluorine is a widely debated issue in Nuclear Astrophysics. It is widely recognized that Asymptotic Giant Branch stars are among the most important contributors to the Galactic fluorine production. Various reaction chains may lead to 19F production, however for some α capture re- actions cross sections at astrophysically relevant energies are determined on the basis of some very poorly known low-energy resonance parameters. Among these the 15N(α, γ)19F reaction is a common feature in the various production channels so far proposed. Its reaction rate at relevant temperatures is determined by a number of narrow resonances together with the direct capture and the tails of the two broad resonances at Ec.m.= 1323 and 1487keV. The broad resonances parameters were measured through the direct detection of the 19F recoil ions with the European Recoil separator for Nuclear Astrophysics (ERNA) were performed. The reaction was initiated by a 15N beam impinging onto a 4He windowless gas target. The observed yield of the resonances at Ec.m. = 1323 and 1487 keV was used to determine their widths in the α and γ channels were determined. While a fair agreement was found with earlier determination of the widths of the 1487 keV resonance, a significant difference was found for the 1323 keV resonance. The experiment, the results and their influence at the temperatures of the 19F stellar nucleosynthesis will be discussed. Outlook on the determination of the direct capture component and the 364 keV narrow resonance, whose uncertainties still dominates the reaction rate, will be also presented.

Speaker: Antonino Di Leva (INFN Napoli)

Abstract 202_DiLevaAntonino.pdf

Slides DiLeva_NIC2018_public_version.pdf

31 The Trojan Horse Method: a versatile tool for nuclear astrophysics

The low energy behavior of reactions of astrophysical interest is one of the most important inputs to calculate the reaction rates of astrophysical importance and therefore to evaluate their impact on several astrophysical environments. Direct measurements in the last decades have given an important contribution to understanding several astrophysical phenomena although they have highlighted an '' unexpected'' problem related to the lowering of the Coulomb barrier between the interacting nuclei due to the presence of the ''electron screening'' in the laboratory measurements. It was systematically observed that the presence of the electronic cloud around the interacting ions in measurements of nuclear reactions cross sections at astrophysical energies gives rise to an enhancement of the astrophysical S(E)-factor as lower and lower energies are explored. Moreover, at present such an effect is not well understood as the value of the potential for screening extracted from these measurements is higher than the upper limit of theoretical predictions (adiabatic limit). On the other hand, the electron screening potential in laboratory measurement is different from that occurring in stellar plasmas thus the quantity of interest in astrophysics is the so-called "bare nucleus cross section". This quantity can only be extrapolated in direct measurements. These are the reasons that led to a considerable growth on interest in indirect measurement techniques and in particular the Trojan Horse Method (THM). Moreover explosive nucleosynthesis, which is dominated by unstable nuclei interacting with p, alpha and n, has helped to trigger the development of radioactive beams facilities worldwide. Notwithstanding the huge experimental difficulties connected to directly measuring cross-section for reactions induced by RIBs at astrophysical energies, this has given more and more credit to indirect methods. An overview of the available indirect methods will be given, with a special attention to the Trojan Horse Method. The basic principles of the Method will be introduced with special attention to its advantages and limits as well as the application to some problems of big astrophysical relevance and the related results.

Speaker: Rosario Pizzone (INFN - LNS)

Abstract ID_020_Pizzone.pdf

Stellar contribution: WDs, Novae SNeIa, & X-ray burst

Convener: Jordi Jose (Dept. Fisica, Univ. Politecnica de Catalunya)

32 Inverse kinematics studies of 20,21Ne(p,γ)21,22Na relevant to 22Na production in oxygen-neon novae with DRAGON

Oxygen-neon (ONe) novae are cataclysmic events resulting from thermonuclear runaway on the surfaces of accreting oxygen-neon white dwarfs in close binary systems, and can reach peak temperatures in the range of T = 0.1 − 0.4 GK [1]. The radioisotope 22Na can be produced and subsequently ejected into the interstellar medium during such events. Sodium-22 β-decays (t1/2 = 2.6 y) primarily to the first excited state in 22Ne, which transitions to its ground state via emission of a 1.275 MeV γ-ray. The combination of long half-life and characteristic γ signature makes 22Na a possible probe of the nuclear physics of novae [2], as γ-rays of this energy are detectable with current orbiting satellite observatories [3]. To date, observation of a 1.275 MeV γ signal from novae has been elusive. The lack of a verifiable detection of a 1.275 MeV γ signal gives an accepted upper limit on the production of 22Na in novae of 3.7E-8M⊙ [4]. The next generation of orbital observatories are expected to have the sensitivity required to detect a galactic 22Na β-decay signal [5], thus minimization of uncertainties underlying 22Na production in novae is desirable for an accurate comparison of novae nucleosynthesis models with astronomical observations. During ONe novae, production of 22Na can proceed via the reaction path20Ne(p,γ)21Na(β+νe)21Ne(p,γ)22Na, which comprises a portion of the neon-sodium cycle in hydrogen burning. Considerable uncertainties exist in the 20,21Ne(p, γ)21,22Na reaction rates. New measurements of 20,21Ne(p, γ)21,22Na have been performed in inverse kinematics using the DRAGON recoil separator [6], with the aim of reducing experimental uncertainties in the thermonuclear reaction rates. Experimental methods and preliminary results will be discussed.

Speaker: Devin Connolly (TRIUMF)

Abstract 155_ConnollyDevin.pdf

Slides NIC_Connolly_20Ne_pg.pptx

13:00 Lunch

Stellar contribution: WDs, Novae SNeIa, & X-ray burst

Convener: Prof. Jordi Jose (Dept. Fisica, Univ. Politecnica de Catalunya)

33 beta-Delayed Charged Particle Detector for Studies of Novae and X-ray Bursts

Classical novae and type I X-ray bursts are energetic and common thermonuclear astrophysical explosions. However, our ability to understand these events is limited by the lack of comprehensive nuclear data on proton-rich nuclei. Specifically, constraining the 30P(p,gamma)31S and 15O(alpha,gamma)19Ne reaction rates has been found to be crucial to the understanding of nucleosynthesis and energy generation in these events. As direct measurements of these reactions are not technically feasible at the present time, indirect measurements of dominant resonance strengths by beta-delayed protons and alpha particles are proposed. A previous measurement at NSCL identified a new 31S state at E_x=6390 keV to be a key resonance for 30P proton capture at peak nova temperatures. A significant branching ratio of 3.38\% from 31Cl beta decay was observed, which enables the determination of the resonance strength by measuring the corresponding 259 keV beta-delayed protons. Similarly, a previous measurement at NSCL observed a 0.0156\% feeding of the 19Ne state at 4034 keV, a key resonance for the 15O(alpha,gamma)19Ne reaction, by the 20Mg(beta p) sequence. This branching ratio is sufficient to determine the resonance strength by measurement of the proton-$\alpha$ pairs. A gas-filled detector of beta-delayed charged particles has been designed and built to measure the aforementioned decays at NSCL. The detector is coupled with the Segmented Germanium Array (SeGA) to enable coincidence gamma detection as an additional probe of the decay scheme and for normalization purposes. The first phase of the detector functions as a proton calorimeter, and it is scheduled to be commissioned with 25Si(beta p)Mg and 23$Al(beta p)22Na during the first week of May 2018. We will report on the performance of the detector and present preliminary beta-delayed proton spectra. References L. N. Downen {et al.}, Astrophys. J. {\bf 762}, 105 (2013). R. H. Cyburt {et al.}, Astrophys. J. {\bf 830}, 55 (2016). M. B. Bennett and C. Wrede {et al.}, Phys. Rev. Lett. {\bf 116}, 102502 (2016). C. Wrede {et al.}, Phys. Rev. C. {\bf 96}, 032801 (R) (2017).

Speaker: Moshe Friedman (NSCL, MSU)

Abstract 165_Friedman.pdf

Slides Friedman_NIC2018_public_version.pdf

34 Study of key resonances in the 30P(p,g)31S reaction in classical novae

Classical novae outbursts are the third most energetic explosions in the Universe after gamma-ray bursts and supernovae. During this explosive burning, nucleosynthesis takes place and the newly synthesized material is ejected into the interstellar medium. In order to understand these objects, the study of presolar grains and gamma-ray emitters are of speci1c interest since they can give direct insights into the nucleosynthesis processes and isotopic abundances. The 30P(p,g)31S reaction is one of the few remaining reactions which rate uncertainty has a strong impact on classical novae model predictions. Sensitivity studies have shown that it has the largest impact on the predicted elemental abundance ratios of Si/H, O/S, S/Al, O/P and P/Al, which can be used to constrain physical properties of classical novae. The 30Si/28Si isotopic ratio, which is an important signature that helps to identify presolar meteoritic grains of a likely nova origin, depends also strongly on the 30P(p,g)31S reaction rate. To reduce the nuclear uncertainties associated to this reaction we performed an experiment at ALTO facility of Orsay using the 31P(3He,t)31S reaction to populate 31S excited states of astrophysical interest and detect in coincidence the protons coming from the decay of the populated states in order to extract the proton branching ratios. After a presentation of the astrophysical context of this work, the current situation of the 30P(p,g)31S reaction rate will be discussed. Then the experiment set up of this work and the analysis of the single and coincidence events will be presented.

Speaker: Anne Meyer (Institut de Physique Nucléaire d'Orsay)

Abstract 102_Meyer.pdf

Slides Meyer_NIC2018_public_version.pdf

Particle Astrophysics

Convener: Matthias Junker (INFN - LNGS)

35 What’s up with dark matter? - Direct dark matter searches

The dark matter problem has accompanied cosmologist and particle physicist for more than 80 years. Nowadays we have an extremely accurate model of our Universe, but still most of its content eludes our observation. The observation of this missing matter is of compelling necessity for our understanding. Direct searches aim to detect dark matter particles with Earth-bound detectors. A review of the most sensitive technologies and of recent results is given together with a glance into the perspectives.

Speaker: Federica Petricca (Max-Planck-Institut für Physik)

Abstract ID_054_Petricca.pdf

Slides Petricca_NIC2018_public_version.pdf

36 Review on Neutrinoless Double Beta Decay

The observation of neutrino oscillations has established non-zero masses of neutrinos, the flavour change and mixing of neutrinos. After these discoveries the global physics community is facing the next challenging problem, whether neutrinos are indeed Majo- rana particles (i.e. identical to its own antiparticle). The search for neutrinoless double beta decay allows in principle fixing of the neutrino mass scale, the neutrino nature (the Dirac or Majorana particles) and possible CP violation effects. A clear detection of the neutrinoless double beta decay will prove the total lepton number (LN) to be broken in nature, and neutrinos to be Majorana particles. In this review history and motivation of neutrinoless double-beta decay are briefly discussed. The status, recent results and advancements of current neutrinoless double-beta decay experiments are reviewed, and requirements and prospects of the new generation of experiments are presented.

Speaker: Matthias Laubenstein (INFN - LNGS)

Abstract ID_205_Laubenstein_NIC2018.pdf

37 Impact of Neutrino Collective Oscillation on Supernova Nucleosynthesis and Mass Hierarchy

Binary neutron-star mergers (NSMs) and core-collapse supernovae (CCSNe, both neutrino-driven winds; ν-wind SNe and magneto-hydrodynamic jets; MHD Jet-SNe) are viable candidate astrophysical sites for the heavy r-process elements. In particular, the observed optical and near-infrared emissions from GW170817 are consistent with those from radiative decays of r-process nuclei which are predicted theoretically. However, specific r-process elements have not yet been identified directly in either NSMs or CCSNe, and it is still under the theoretical debate if the “universality” for heavy nuclides above the 2nd peak to actinides is explained by only the NSM r-process, SN r-process, or both [1,2]. In this paper, we would like to propose an alternative approach to the "universality" especially on the 1st peak. The elements whose masses are in the range of A = 80-100 near the 1st r-process peak have several possible nucleosynthetic processes such as r-, s-, rp-, γ-, νp-processes, etc. Although the ν-wind SNe are presumed to be the leading candidate astrophysical site for the 1st r-process peak elements like As-Se-Br, an required neutron-rich condition (Ye < 0.5) has been put into question by failures of robust models for SNe if one assumes only the neutrino heating source to trigger a successful explosion. However, we find that the νp-process operates strongly with amounts of free neutrons being supplied continuously in the proton-rich (Ye > 0.5) materials via p(νe, e-)n reactions when one takes account of the effects of collective neutrino oscillations in coherent self-interacting neutrino scatterings (collective νp-process) [3]. We then find that the nuclear reaction flows can reach the production of abundant p-nuclei like 92Mo, 96Ru, etc. for the mass region of A < 100, which are in reasonable agreement with the observed abundance ratios of the solar-system p-nuclei. This nucleosynthetic method turns out to be a unique probe indicating the still unknown neutrino-mass hierarchy [3]. We currently study extensively if our proposed collective νp-process and the r-process in CCSNe and NSMs can explain the "universality". [1] S. Shibagaki, T. Kajino, G. J. Mathews et al., ApJ 816 (2016), 79. [2] T. Kajino & G. J. Mathews, Rep. Prog. Phys. 80 (2017), 084901. [3] H. Sasaki, T. Kajino, T. Takiwaki et al., Phys. Rev. D96 (2017), 043013.

Speaker: Taka Kajino (National Astronomical Observatory of Japan)

Abstract 38_Kajino.pdf

Slides Kajino_NIC2018_public_version.pptx

38 The impact of axions on Mup

Axions are weak interactive bosons early introduced to solve the longstanding CP violation problem of strong interaction. If their mass is small enough (few keV or smaller), they can be produced in stellar interior, e.g., by Compton, Bremsthalung, pair annihilations or Primakoff processess, acting as an additional energy loss mechanism. We study the effect of axions in the evolution of stellar masses that are close to the minimum stellar mass that experiences central carbon burning, Mup. This mass limit is a fundamental property in astrophysics as it defines which stars produce carbon-oxygen white dwarfs (CO WDs) and, at the other side, those that produce oxygen-neon white dwarfs, electron-capture supernovae and normal core collapse supernovae (CCSNe). Hence, this mass limit is critical for the WD mass distribution, supernova progenitors, supernova rates, chemical evolution of galaxies and so on. We explore a set of values for the axion coupling constant to photons and electrons, within current constraints. Our results show that axions may increase Mup till values that are in tension with the observationaly derived minimum mass of CCSNe progenitors and with the maximum stellar mass that produces a CO WD. This is the first study that considers axion effect in this stellar mass range, and on Mup.

Speaker: Inma Dominguez (Universidad de Granada)

Abstract 126_DominguezInma.pdf

Slides Dominuez_NIC2018_public_version.pdf

39 The Neutrino Signal From Pair Instability Supernovae

Pair-instability supernovae (PISNe) are the explosions of very massive stars with carbon-oxygen cores in the range of 64 Msun to 133 Msun. These kind of supernovae are candidates for some observed superluminous supernovae although recent studies suggest PISNe in the local Universe may be much dimmer and hidden among other supernova classes. While observations of PISNe using electromagnetic radiation may be able to distinguish these supernovae from the other types, a much clearer and unambiguous difference is found in the neutrino emission. In this talk I present the first ever calculations of the neutrino signal from pair-instability supernovae using two hydrodynamical simulations chosen to bracket the mass range of the carbon-oxygen core. We take into account both the full time and energy dependence of the emission and the flavor oscillations through the mantle of the star, as well as investigating equation-of-state and line-of-sight differences. We then process the computed neutrino fluxes at Earth through five different neutrino detectors chosen to represent the range of current or near-future technologies. I will show how the neutrino signal from PISNe possesses unique features that distinguish it from other supernovae, how the detectors we consider are capable of observing neutrinos from PISNe at the ‘standard’ distance of 10 kpc, and how the proposed HyperKamiokande detector can even reach the Large Megallanic Cloud and the several very high mass stars known to exist there.

Speaker: James Kneller (NC State University)

Abstract 5_Kneller.pdf

Slides Kneller_NIC2018_public_version.pdf

40 Neutrinos from Presupernova Stars

Some evolved massive stars such as Betelgeuse and Antares are located at the distance of hundreds parsec. When such a star explodes as a supernova, neutrino events will be observed by current and future neutrino detectors even before the supernova explosion, i.e., the neutrinos from the presupernova star will be detected. The neutrino event rate in neutrino detectors during silicon burning of massive stars has been evaluated by considering neutrino emission by pair-neutrino process (Odzywolek et al. 2004). Recently, detailed studies on neutrino events from presupernova stars have been carried out using the evolution data of massive stars from silicon burning (e.g., Kato et al. 2015, Asakura et al. 2016, Yoshida et al 2016, Kato et al. 2017). We investigate the evolution of the neutrino spectra from the silicon burning until the core-collapse of 12, 15, and 20 solar-mass stars. Then, we evaluate the neutrino events by current neutrino detectors, KamLAND and Super-Kamiokande, and by future neutrino detectors, JUNO, Hyper-Kamiokande, and DUNE. We discuss the possibility of the observations of stellar interior just before the supernova explosions using the time variation of neutrino events from the presupernova stars (Yoshida et al. 2016). We evaluate the inverse beta-decay events by KamLAND before a supernova explosion. The event number is expected to be 4-14 for seven days before the supernova. The variation is mainly due to the progenitor mass and neutrino mass hierarchy. We also evaluate the supernova alarm time using the presupernova neutrino events of KamLAND. The expected alarm time for a supernova explosion is 3.5-18 hours and less than 3.6 hours for the normal and inverted mass hierarchies, respectively. We expect that earlier supernova alarm is possible in future neutrino detector JUNO. The time variation of the neutrino events per unit time can be a good indicator for observing stellar interior just before the supernova explosion. The expected neutrino events per one hour by JUNO usually increase with time. However, we also expect the reduction and a minimum at about ten hours before the explosion in the 15 solar-mass star model. This reduction corresponds to the ignition of the oxygen shell burning. Thus, the time variation of the neutrino events would reveal the stellar interior and burning processes just before the supernova explosion.

Speaker: Takashi Yoshida (University of Tokyo)

Abstract 170_Yoshida.pdf

Slides 180626tyoshida.pdf

17:00 Coffee break

Galactic chemical evolution

Convener: Maria Lugaro (Konkoly Observatory)

41 Dynamical and chemical evolution of the Milky Way from Optical and IR spectroscopic Surveys

In the last decade or so a variety of ground based spectroscopic surveys of the Milky Way have been undertaken. These projects are yielding accurate kinematics and abundances for large, statistically significant samples of stars belonging to different Galactic populations. I will review the main results from those surveys, and discuss their huge impact on our understanding of the chemical and dynamical evolution of the Galaxy, as well as on stellar nucleosynthesis.

Speaker: Sofia Randich (INAF - OAA)

Abstract ID_182_Randich.pdf

Slides randich_forweb.pdf

42 Galactic chemical evolution and the role of rotating massive star yields

Speaker: Nikos Prantzos (Institut d'Astrophysique de Paris)

Abstract ID_213_Abstract_Prantzos.pdf

43 Heavy element production:merging neutron stars versus supernovae

I will discuss the Eu production in the Milky Way under different assumptions about its nucleosynthesis. In particular, Eu formation via merging neutron stars and supernova core-collapse will be discussed in the light of the results from a detailed chemical evolution model that will be compared with the abundances of Eu in stars of the solar vicinity.The formation of Eu via merging neutron stars seems to be favored by chemical evolution results, and I will suggest that this is the dominant mechanism for the formation of heavy nuclei, such as Eu,in the light of the gravitational event GW170817 detected by Ligo/Virgo.The various assumptions and leastuncertainties on. i) the time delay for neutron star merging, ii) the progenitors of neutron stars and iii)the stellar yields will be critically dicussed.

Speaker: Maria Francesca Matteucci (INAF - OATS)

Abstract 95-Matteucci.pdf

44 Inhomogeneous Galactic Chemical Evolution of r-process Elements

The origin of the heaviest elements is still a matter of debate. For the rapid neutron capture process (r -process), multiple sites have been proposed, e.g., neutron star mergers and (sub-classes) of supernovae. R-process elements have been measured in a large fraction of metal-poor stars. Galactic archaeology studies show that the r-process abundances among these stars vary by over 2 orders of magnitude. On the other hand,abundances in stars with solar-like metallicity do not differ greatly. This leads to two major open questions: 1. What is the reason for such a huge abundance scatter of r -process elements in the early galaxy? 2. While the large scatter at low metallicities might point to a rare production site, why is there barely any scatter at solar metallicities? We use the high resolution ( 20 parsec/cell) inhomogeneous chemical evolution tool ”ICE” to study the role of the contributing source(s) of r-process elements. In this talk, I will discuss chemical evolution scenarios that provide an explanation for the observed abundance features of r-process elements in our Galaxy.

Speaker: Benjamin Wehmeyer (North Carolina State University)

Abstract ID_046_Wehmeyer_abstract.pdf

Poster session

45 15N(α,γ)19F measurement for 19F production in AGB stars

15N(α,γ)19F is known to be one of the key formation mechanisms of 19F in AGB stars [1]. 19F may also be produced through this reaction in other stars such as Wolf-Rayet stars [2]. The 19F abundance observed in the stellar spectra strongly depends on the conditions in the astrophysical site. Its nucleosynthetic origin has been debated for several decades, however the understanding of the 15N(α,γ)19F reaction rate within the Gamow window at 200 MK for AGB stars is incomplete. Discrepancies in strength and energy exist between previous measurements in one of the key resonances, at Ec.m.=1.323 MeV. Furthermore, the direct-capture, non-resonant cross-section has never been directly measured. The DRAGON recoil separator at TRIUMF was utilised to perform an inverse kinematics measurement of the 15N(α,γ)19F reaction. Recoiling 19F nuclei leaving the windowless helium gas target were separated using DRAGON’s electromagnetic mass separator and detected in a DSSSD. Emitted gamma-rays from the de-excitation of the compound nucleus were detected in a BGO array surrounding the target and used for a coincidence analysis. We have measured the strength and energy of the Ec.m.=1.323MeV resonance in the 15N(α,γ)19F reaction as well as the direct-capture cross section down to an energy of Ec.m.=0.96 MeV. The 2017 ERNA measurement by Di Leva et al. [3] was the first time 15N(α,γ)19F was measured in inverse kinematics; two strong reference resonances were measured. This measurement at DRAGON is the second inverse kinematics measurement. Our new measurement of the Ec.m.=1.323MeV resonance will help in solving the existing discrepancies regarding its strength, and provides an independent measurement of its energy, as well as the first measurement of the direct-capture contribution in the low-energy regime. This measurement will reduce uncertainties in 15N(α,γ)19F reaction rate, especially in the direct-capture component where no previous measurements exist, thus helping to refine our understanding of AGB models and 19F production. References [1] O. Staneiro et al., The Astrophysical Journal. 785 (2014) 77. [2] G. Meynet and M.Arnould, A& A. 335 (2000) 176. [3] A. Di Leva et al., Phys. Rev. C. 95 (2017) 045803.

Speaker: Joseph Frost-Schenk (University of York)

Abstract 114_Frost-Schenk.pdf

46 7Be(p,p)7Be and its Importance in Nuclear Astrophysics

Proton-induced reactions on 7Be play an important role in nuclear astrophysics studies related to solar neutrinos. Recent Earth-bound experiments measuring solar neutrino fluxes from the Sun show discrepancies between both within each other and with the standard solar model (SSM). Of the reactions involved in the production of solar neutrinos, the 7Be(p,g)8B still carries the largest uncertainties. Studies have been performed of both 7Be(p,g)8B and 7Be(p,p)7Be. To further constrain its S-factor at relevant energies, a precise study of the 7Be(p,p)7Be elastic scattering will be carried out at CIRCE (Centre for Isotopic Research on Cultural and Environmental heritage) in Caserta, Italy. Data will help to constrain the 7Be(p,g)8B reaction cross section through a global R-matrix analysis. The ultimate drive of this effort in understanding the neutrino discrepancies is to use the Sun as a standard in the comparison to other stars across the Universe. A brief description of the CIRCE accelerator and target chamber, and an update of the work carried out so far will be presented.

Speaker: Thomas Chillery (University of Edinburgh)

Abstract 096_Chillery.pdf

47 A 400kV High Intensity Accelerator facility for Jinping Underground Nuclear Astrophysics Experiments

Direct measurement of the cross sections for the key nuclear reactions is crucial for obtaining benchmark data for stellar model, verifying extrapolation model, constraining theoretical calculations, and solving key scientific questions in nuclear astrophysics. However, reaction cross-sections of the astrophysical reactions are extremely small. Tiny reaction rates in laboratories at the earth's surface are hampered by the cosmic-ray background. With the ultra-low underground lab becomes a promising solution of experimental nuclear astrophysics. China JinPing Underground Laboratory (CJPL) is currently deepest underground site in the word. For such experiments, a 400kV, 10mA accelerator specially designed for Jinping Underground Nuclear Astrophysics (JUNA) will be placed in CJPL. In this paper the layout and design considerations of accelerator, such as beam optics, high intensity beam accelerating, transmission and other special features applied in the Jinping deep underground lab are presented.

Speakers: Lihua Chen (China Institute of Atomic Energy), Weiping Liu (China Institute of Atomic Energy)

Abstract 118_Chen.pdf

48 A BGO set-up for the 2H(p,g)3He cross section measurement at the BBN energy range

Deuterium is the first nucleus produced in the Universe, whose accumulation marks the beginning of the so called Big Bang Nucleosynthesis (BBN). Presently the main obstacle to an accurate theoretical deuterium abundance evaluation is due to the poor knowledge of the 2H(p,g)3He cross section at BBN energies. The fusion cross section of the reaction is under studying at LUNA (Laboratory for Underground Nuclear Astrophysics) in the energy range of interest (30 < Ecm[keV] < 300). The experiment consists of two main phases characterized by two different setups. The present poster is focused on the first one based on a windowless gas target filled with deuterium together with a BGO detector. The scintillator crystal is optically divided into six sectors, each covering a 60° azimuthal angle, granting a configuration geometry close to 4p. Thanks to its high detection efficiency (about 60% in the energy range of interest) this setup will provide measurements down to very low energies. The present poster will report on the BGO phase of the experiment. The characterization of the setup, background conditions, and potential sources of uncertainty will be discussed.

Speaker: Viviana Mossa (Bari University & INFN)

Abstract 174-Mossa.pdf

49 A collapsar model with disk wind: implications for supernovae associated with a gamma-ray burst

We construct a simple but self-consistent collapsar model for gamma-ray bursts (GRBs) and SNe associated with GRBs (GRB-SNe).Our model includes a black hole, an accretion disk, and the envelope surrounding the central system.The evolutions of the different components are connected by the transfer of the mass and angular momentum. To address properties of the jet and the wind-driven SNe, we consider competition of the ram pressure from the infalling envelope and those from the jet and wind. The expected properties of the GRB jet and the wind-driven SN are investigated as a function of the progenitor mass and angular momentum. We find two conditions which should be satisfied if the wind-driven explosion is to explain the properties of the observed GRB-SNe. (1) The wind should be collimated at its base, and (2) it should not prevent further accretion even after the launch of the SN explosion. Under these conditions, some relations seen in the properties of the GRB-SNe could be reproduced by a sequence of different angular momentum in the progenitors. Only the model with the largest angular momentum could explain the observed (energetic) GRB-SNe, and we expect that the collapsar model can result in a wide variety of observational counterparts mainly depending on the angular momentum of the progenitor star.

Speaker: Tomoyasu Hayakawa (Kyoto University)

Abstract 157-Hayakawa.pdf

50 A new experimental technique for measuring (p,n) reactions relevant to the neutrino-p process in the ReA3 facility

Neutrino driven winds (NDW) in core-collapse supernovae (CCSN) constitute an important astrophysical environment for nucleosynthesis, especially for the formation of elements beyond iron. If the right proton-rich conditions are found in the wind, nuclei with atomic numbers up to Z~50 can be produced via the so called neutrino-p (vp-) process. The strength of vp-process depends on a few key (n,p) reactions like the 56Ni(n,p)56Co and 64Ge(n,p)64Ga for which currently no experimental data exist. With the current state-of-the-art, any direct measurement of (n,p) reactions on neutron-deficient nuclei is extremely challenging. For this purpose, a new experimental technique is under development at the ReA3 facility of the National Superconducting Cyclotron Laboratory for the study of astrophysically important (n,p) reactions via measuring their time-reverse (p,n) reactions in inverse kinematics. The main point of this technique is the separation of the heavy reaction products from the unreacted beam. This is properly achieved by operating a section of the ReA3 beam line as a recoil separator while using the LENDA neutron detector to tag the neutrons from the (p,n) reaction. At this stage, a proof-of-principle experiment has been performed using a stable 40Ar beam at 3.52 MeV/u in order to measure the 40Ar(p,n)40K reaction. In this presentation, a detailed description of the experimental method and results from the first proof-of-principle run will be shown. *This research project is funded by the U.S. Department of Energy, Office of Science

Speaker: Panagiotis Gastis (Central Michigan University)

Abstract 108_Gastis.pdf

51 A public code for precision big bang nucleosynthesis with improved Helium-4 predictions

Now that the number of neutrino families and the baryonic density have been fixed by laboratory measurements or CMB observations, big bang nucleosynthesis has no free parameter. Hence, it is possible to accurately calculate the abundances of the produced light elements. It is now well known that there is a, yet unexplained, discrepancy of a factor of approx 3 between the primordial abundance deduced from observations of halo stars, and the BBN predictions. Recently, the precisions on primordial abundances of both deuterium and helium-4, deduced from observations, have been drastically improved and are now close to the percent level. Accordingly, the BBN predictions should reach the same level of precision. For most isotopes, the dominant sources of uncertainty come from those on the laboratory thermonuclear reactions rates. The exception is helium-4 whose predicted primordial abundance depends essentially on the theoretical weak interaction rates which control the neutron-proton ratio. These rates depend on the experimentally measured neutron lifetime, but also includes numerous corrections that affects both deuterium and helium-4 predictions at levels comparable to the observational uncertainties. A primordial nucleosynthesis code that incorporates, not only these corrections but also a full network of reactions, using the best available thermonuclear reaction rates, allowing the predictions of primordial abundances of helium-4, deuterium, helium-3 and lithium-7 but also of heavier isotopes up to the CNO region is now publicly available at http://www2.iap.fr/users/pitrou/primat.htm. It can be used to reproduce the Ref. standard calculations, implement new physics, or simply test new reaction rates. References A. Coc, E.Vangioni, {Int. J. Mod. Phys. E.} {\bf 26} (2017) 1741002, {\tt arXiv:1707.01004}. C. Pitrou, A. Coc, J.-P. Uzan \& E. Vangioni, (2018), {\tt arXiv:1801.08023}.

Speaker: Alain Coc (CSNSM Orsay)

Abstract 098_Coc.pdf

52 Accelerator mass spectrometry measurement of the reaction 92Zr(n,gamma)93Zr at stellar energies

Zirconium isotopes are predominantly produced by the slow neutron capture process. Maxwellian averaged cross sections (MACS) for neutron capture in the keV region are one of the key parameters to model this astrophysical process. They are particularly interesting in the mass region between 90-100 amu, as this is the matching area between the main and the weak component of the \text-process, taking part in two different stellar environments. However, significant uncertainties in the experimental data and deviations between theoretical predictions and experimental data for several neutron capture reactions in this mass region remain. A combination of activation technique and accelerator mass spectrometry (AMS) was used to determine the MACS of the reaction 92Zr(n,gamma)93Zr. This method provides a different approach compared to previous time-of-flight (TOF) measurements and hence addresses different systematic uncertainties. Zirconium oxide pellets enriched in 92Zr were irradiated with a quasi-Maxwellian neutron spectrum of 30 keV at the Liquid Lithium Target beamline of the Soreq Applied Research Accelerator Facility. AMS measurements of the reaction product 93Zr were performed at the Heavy Ion Accelerator Facility (HIAF) of the Australian National University in Canberra. The main challenge in AMS of 93Zr is the interference from the stable isobar 93Nb. The high particle energies available at HIAF are ideal to tackle this challenge. Recently we have developed the technique to measure $^{93}$Zr with the required sensitivity and efficiency for such studies. Here we will present preliminary AMS results for the 92Zr(n,gamma)93Zr capture cross section, which were found to be in fair agreement with the latest TOF measurement by Tagliente et al. References G. Tagliente et al. (The n-TOF collaboration), Phys. Rev. C {81}(2010)055801.

Speaker: Stefan Pavetich (The Australian National University)

Abstract Pavetich_abstract_NIC2018.pdf

53 Activation cross section measurements of the 92,94,100Mo(a,n)95,97,103Ru reactions and optical potentials for modelling explosive nucleosynthesis scenarios

Alpha-nucleus optical model potentials (OMP) are widely used in nuclear reaction network calculations aiming at the study of the gamma-process [1] and the weak r-process [2]. Considerable theoretical and experimental effort has been devoted in recent years to improve the knowledge of the OMP’s in order to give correct predictions for the cross sections and reaction rates [3,4] (and references therein). Recently, (a,n) cross section measurements on 92,94,100Mo are in progress at ATOMKI using the activation technique. The resulted cross sections have been used to test the predictions of global optical potential parameterizations used in modelling the gamma-process and the weak r-process. The experimental details and preliminary results will be presented. [1] T. Rauscher et al., Reports on Progress in Physics 76 6201 (2013). [2] Y. Qian et al., Phys. Rep. 442 237 (2007). [3] T. Szücs et al., Phys. Lett. B 776 396 (2018). [4] G. G. Kiss et al., Phys. Rev. C 88, 045804 (2013).

Speaker: Tibor Norbert Szegedi (ATOMKI)

Abstract 092_Szegedi.pdf

54 Al-26 yields from massive single and binary stars

Aluminium-26, a radioactive isotope with a half life of 0.72 Myr, was present in the early Solar System, as inferred from 26 Mg excess in meteorites, see e.g. [1]. It is also detected in the Galaxy via γ-ray observations from COMPTEL and INTEGRAL, see [2]. While it is known that 26 Al is produced in stars, many uncertainties are left related to the production sites and the nuclear physics input. Past research has focused mostly on yields of 26 Al from massive single stars, both rotating and non-rotating, including their winds and supernova explosions, see [3], [4], [5], and [6]. Here we present my planned research that will focus on the yields from massive star winds, primarily Wolf-Rayet stars (>30M), both single and in binary systems, and on the yields from non-conservative mass transfer in binary systems with primary masses >15M . The final goal is to discover the impact of massive binary stars on the galactic abundance of 26 Al and on the origin of the 26 Al in the early Solar System. References [1] Jacobsen, B. et al., 2008, Earth and Planetary Science Letters, 272, 353 [2] Diehl, R., 2013, Reports on Progress in Physics, 76, 026301 [3] Limongi, M. and Chieffi, A., 2006, ApJ, 647, 483 [4] Chieffi, A., and Limongi, M., 2013, ApJ, 764, 21 [5] Ekström, S. et al., 2012, AAP, 537, 146 [6] Woosley, S. E. and Heger, A., 2007, Physics Reports, 442, 269

Speaker: Hannah Brinkman (Konkoly Observatory, Hungary)

Abstract 75_BrinkmanHannah.pdf

55 Alpha-capture reaction rate for 22Ne(alpha,n) via sub-Coulomb alpha-transfer and its effect on final abundances of s-process isotopes

The 22Ne(alpha,n) reaction is a very important neutron source reaction for the slow neutron capture process (s-process) in asymptotic giant branch stars. Direct measurements are extremely difficult to carry out at Gamow energies due to the extremely small reaction cross section. The large uncertainties introduced when extrapolating direct measurements at high energies down to the Gamow energies can be overcome by determining the partial alpha-width of the relevant states in indirect measurements. This can be done using alpha-transfer reactions at sub-Coulomb energies to reduce the dependence on optical model parameters. The alpha-transfer reaction of 22Ne(6Li,d)26Mg was carried out at the Cyclotron Institute at Texas A&M University to study this reaction. It appears that the widths of the near alpha-threshold resonances of 26Mg are quite different for similar 22Ne(6Li,d) reactions carried out previously using different energies. This discrepancy affects the final 22Ne(alpha,n) reaction rate and thus the final abundances of the s-process isotopes.

Speaker: Heshani Jayatissa (Texas A&M University)

Abstract jayatissa-abstract-2017.pdf

56 Ambient Neutron Background in the Shallow-Underground Laboratory Felsenkeller

One important component of the ambient background in underground laboratories are neutrons, which may cover a wide energy range from thermal up to 100 MeV and may affect γ-ray spectra for example by capture and inelastic scattering processes. Underground with more than a few meters rock overburden, cosmic-ray neutrons are removed, and the remaining flux is due to neutron production by cosmic-ray muons and by (α,n) reactions caused by natural radioactivity in the rock. There are only a few measurements of the spectral neutron flux underground available in the literature, a fact which hampers comparisons between laboratories and negatively affects the planning of future experiments. In an effort to overcome this problem, a setup consisting of moderated and one unmoderated 3 He neutron counters that has already been used at a depth of 850 m in the Canfranc underground laboratory, Spain [1], was utilized to study the neutron flux in the 47 m deep Felsenkeller underground laboratory, Germany. At Felsenkeller, one more counter with a lead liner was added in order to address also the high-energy flux up to several hundreds of MeV. The contribution will describe the Monte Carlo modeling of the neutron detectors, its validation with calibrated neutron sources, the spectral deconvolution of the neutron flux, and the final neutron flux data. Potential normalization issues in previous measurements will be discussed. The experimental neutron flux data at Felsenkeller are matched by a Monte Carlo simulation starting from the measured muon flux (for the muon-induced neutrons) and the known ambient radioactivity of the rock and construction materials (for the (α,n) neutrons). The present data have influenced the planning of the new laboratory hosting the 5 MV Pelletron ion accelerator in Felsenkeller.

Speaker: Thomas Hensel (Helmholtz-Zentrum Dresden-Rossendorf)

Abstract 69_HenselThomas.pdf

57 Assessment of Stellar Nucleosynthesis Abundances using ENDF/B-VIII.0 and TENDL-2015 Evaluated Nuclear Data Libraries

Evaluated Nuclear Data File (ENDF) libraries contain complete collections of reaction cross sections, angular distributions, fission yields and decay data. These data collections have been used worldwide in nuclear industry and national security applications. It represents a great interest to explore the recently-released ENDF/B-VIII.0 library for nuclear astrophysics purposes and compare findings with the predictions of Talys Evaluated Nuclear Data Library (TENDL-2015) and Karlsruhe Astrophysical Database of Nucleosynthesis in Stars (KADoNiS). The Maxwellian-averaged cross sections (MACS) and astrophysical reaction rates were calculated using the ENDF/B-VIII.0 and TENDL-2015 evaluated data sets. The calculated cross sections were combined with the solar system abundances and fitted using the classical model of stellar nucleosynthesis. Astrophysical rapid- and slow-neutron capture, r- and s-processes, respectively, abundances are extracted from the present data and compared with available values. Further analysis of MACS reveals the potential astrophysical data deficiencies and strong needs for new measurements. The current results demonstrate large nuclear astrophysics potential of evaluated libraries and mutually beneficial relations between nuclear industry and research efforts.

Speaker: Boris Pritychenko (Brookhaven National Laboratory)

Abstract 51_PritychenkoBorys.pdf

58 Background studies with actively vetoed germanium gamma-ray detector in Felsenkeller tunnels VIII and IX

A new underground accelerator facility is being built in tunnels VIII and IX of the Dresden Felsenkeller. Previous gamma-ray background measurements in another part of the tunnel system showed suitable conditions for in-beam nuclear astrophysics experiments [1,2] using germanium detectors with active veto against the cosmic-ray muons. These stable ion beam experiments are of high importance to understand the reactions of the stellar burning phases, and in particular the solar fusion reactions. The new laboratory is now ready to host measurements mapping the background conditions. This work reports on the measured background in actively vetoed gamma-ray detector at the place of the target station in the laboratory used for the upcoming experiments. [1] T. Szücs et al., Eur. Phys. Jour. A 48 (2012) 8. [2] T. Szücs et al., Eur. Phys. Jour. A 51 (2015) 33.

Speaker: Tamás Szücs (Helmholtz-Zentrum Dresden-Rossendorf)

Abstract 45_SzucsTamas.pdf

59 beta-decay feeding from 69,71Co determined from total absorption spectroscopy measurements

The r process is known to produce roughly half of the abundance of the isotopes of heavy elements. Models of the r-process depend upon theoretical calculations of various nuclear properties such as those from QRPA and Hauser-Feshbach. Sensitivity studies have shown that the final abundance distributions of r-process nuclei are greatly impacted by uncertainties in nuclear masses, neutron-capture rates, as well as beta-decay properties. More specifically, beta-decay half-lives and beta-delayed neutron branching ratios depend on an accurate knowledge of the $\beta$-decay strength function. For this reason, $\beta$-decay intensities for 69,71Co were determined using the technique of total absorption spectroscopy at the National Superconducting Cyclotron Laboratory at Michigan State University. This technique allows us to overcome the so-called ``pandemonium effect, which can cause beta-feeding intensities to high-lying excitation energies to be missed in traditional beta-decay studies. The high Q-values of both 69Co and 71Co allow for the study of beta-decay properties over a broad energy range. The resultant beta-decay intensities and deduced Gamow-Teller strength distributions will be presented and compared to theoretical calculations, including QRPA.

Speaker: Stephanie Lyons (National Superconducting Cyclotron Laboratory)

Abstract 111_Lyons.pdf

60 Carbon burning in stars: An experimental study of the 12C+12C reactions towards astrophysical energies

12C+12C reactions are among the most important processes in the evolution and nucleosynthesis of massive stars. The measurement of these reactions at astrophysical energies is very challenging due to their extremely small cross sections, heavy resonant structure and the presence of natural hydrogen and deuterium contaminants in the carbon targets. To date, no measurement of the 12C+12C reactions has been possible at energies below Ecm=2.14MeV. In addition, measurements at Ecm<3.0MeV present large uncertainties due to the target H contamination. In this work, the measurement of the 12C+12C reactions at Ecm=2.52-4.30MeV was performed using the CIRCE accelerator in Caserta, Italy. We used the dE-Erest particle identification technique to unequivocally identify protons and alpha particles. The 12C+12C reactions cross sections and S-factors were extracted from the thick target yield. The experimental results as well as their impact on the determination of the stellar rate of 12C+12C fusion reactions are discussed.

Speaker: Elia Lizeth Morales Gallegos (INFN Napoli)

Abstract abstract_Morales-Gallegos.pdf

61 Charged-particle branching ratios of excited 19F states and implications for 15N and 18O enrichment in presolar grains

See attached file.

Speaker: Philip Adsley (IPN Orsay)

Abstract 085_Adsley.pdf

62 Core-Collapse supernovae and the impact of finite-temperature microphysics

Core-collapse supernovae represent one of the most energetic events in the universe and are the production site of many elements. The evolution during and after the supernova explosion is key for nucleosynthesis. In both phases, the equation of state (EOS) plays an important role determining the contraction and cooling of the neutron star and thus affecting the ejecta conditions. However, the EOS is still not fully understood and topic of current research in nuclear physics as well as in astrophysics. In this work, we investigate the influence of the EOS in core-collapse supernovae simulations. The impact of finite-temperature microphysics on the explosion phase and the contraction behaviour of the proto-neutron star is analyzed. --- This work is supported by the DFG through Grant SFB 1245.

Speaker: Hannah Yasin (Technische Universität Darmstadt)

Abstract 60_YasinHannah.pdf

63 Core-collapse supernovae: long-time evolution and nucleosynthesis

Core-collapse supernovae play a central role in the chemical history of the universe: they eject alpha elements that are produced during the life of massive stars, produce iron group elements and probably also elements up to Silver or even higher in some extreme cases. In order to investigate the nucleosynthesis occurring in core-collapse supernova, multidimensional simulations are required following the explosion and evolution of the ejecta afterwards. We present two-dimensional simulations starting from the progenitor and following the collapse, explosion and post-explosion evolution for several seconds after bounce. The influence of neutrinos is explored by modifying the neutrino energy deposition rate. Additionally we investigate the impact of rotation on the post-explosion expansion by varying the angular momentum of the progenitor. The nucleosynthesis in the supernova is studied in a post-processing step using information from lagrangian tracer particles in a complete nucleosynthesis network. Supported by the ERC 677912 EUROPIUM grant.

Speaker: Maximilian Witt (Technische Universität Darmstadt)

Abstract 089_Witt.pdf

64 Cosmic Rays and the Production of Lithium in the Small Magellanic Cloud

Lithium is one of the few elements produced in the Big Bang Nucleosynthesis (BBN), but it is the only one with the expected primordial abundances that do not match the observed values measured in low-metallicity environments, like in the Milky Way halo stars. Recently, the first lithium detection outside of the Milky Way was made in the low- metallicity gas of the Small Magellanic Cloud. These abundances are in fact much higher than in the Milky Way halo stars, and are at the level of the expected primordial value. After BBN, lithium is produced in cosmic-ray interactions. Any measured lithium abundance therefor contains at least some post-BBN produced lithium. Cosmic-ray collisions with atoms in the interstellar medium that can produce lithium can also produce gamma-rays, through production of neutral pions and their subsequent decay. In Ciprijanovic (2016) we use the Small Magellanic Cloud gamma-ray observations by Fermi-LAT in order to calculate the abundance of lithium that was produced by galactic cosmic rays in this galaxy. We find that cosmic rays accelerated in supernova remnants inside this galaxy can account for only a small amount of lithium, less than 1% of the observed abundance. The observed lithium abundance that is inconsistent with expected star-formation history of the SMC might indicate that another production channel of lithium was dominant in the SMC, or a more interesting history.

Speaker: Aleksandra Ćiprijanović (Department of Astronomy, Faculty of Mathematics, University of Belgrade)

Abstract 2_CiprijanovicAleksandra.pdf

65 Cosmic-Ray Nucleosynthesis in Galactic Interactions

It has been shown that galactic interaction and mergers can result in large-scale tidal shocks that propagate through interstellar gas. As a result, this can give rise to a new population of cosmic rays, additional to standard galactic cosmic rays present in star-forming galaxies. We investigate the impact of this tidal cosmic-ray population on the nucleosynthesis of lite elements. We especially focus on only extragalactic systems where lithium has been measured in gas phase but which have been disturbed by galactic interactions, namely the Small Magellanic Cloud and the M82. Moreover we also demonstrate that the presence of these tidal shock-waves and may also have far reaching consequences on our understanding of galactic evolution by affecting the far-infrared radio correlation observed in star-forming galaxies and impacting star formation rates estimates.

Speaker: Tijana Prodanovic (University of Novi Sad)

Abstract 206-Prodanovic.pdf

66 Cross section measurements related to the astrophysical p-process

After tremendous experimental and theoretical efforts and significant progress in astrophysical modeling, the origin of the heavy, proton rich isotopes -- the p nuclei -- is still not fully understood. One thing is certain: improved knowledge of the nuclear reactions rates entering the p-process models is crucial. A systematic study of low energy proton and alpha induced reactions on heavy isotopes has been going on for about two decades at Atomki in Debrecen, Hungary. The measured cross sections are compared to theoretical calculations with the aim of improving the reliability of the calculated reaction rates for the astrophysical models. In this talk the recent activities in this field will be summarized. Experimental techniques of cross section measurements on e.g. 121,123Sb, 124Xe, 191,193Ir, 197Au as well as some results will be presented.

Speaker: György Gyürky (ATOMKI)

Abstract 125_Gyurky.pdf

67 Cross-section Measurements of the 94Mo(g,n) and 90Zr(g,n) Reactions Using Real Photons at the HIgS Facility

The photodisintegration reaction cross-sections for 94Mo(γ,n) and 90Zr(γ,n) have been experimentally investigated with quasi-monochromatic photon beams at the High Intensity γ-Ray Source (HIγS) facility, Triangle University Nuclear Laboratory (TUNL). The measurements were focused primarily on studying the energy dependence of the photoneutron cross sections, which is the most direct way of testing statistical models, and were performed close to the respective neutron thresholds and above up to ~ 14 MeV. Neutrons from the (γ,n) reactions were detected using a 4π assembly of 3He proportional counters developed at Los Alamos National Laboratory, presently available at TUNL. The 94Mo(γ,n) and 90Zr(g,n) cross section measurements aim to contribute to a broader investigation for understanding the p-process, the mechanism responsible for the nucleosynthesis of p-nuclei. Our results help to constrain QRPA calculations of γ-ray strength functions in this mass region and show how sensitive the photoneutron rates of astrophysical interest can be to experimental data in the vicinity of the neutron threshold.

Speaker: Adriana Banu (James Madison University)

Abstract abstractBanuNIC2018.pdf

68 Detailed Nucleosynthesis Calculations from Pair-Instability Supernovae

With the advent of high-cadence, full-sky surveys, the number of observed transient events has increased at an astonishing rate. Though the majority of these events display light curves and spectra that fit within the normal classification schemes, a growing number require further explanation. Pair-instability supernovae (PISNe), the disruption of very high-mass (>100Msolar) stars by explosive oxygen burning, present a possible explanation for many of these objects. Given the large progenitor masses, PISNe should have occurred more frequently in the past, and the signatures of these objects may be found in the atmospheres of old, metal-poor stars. In this talk, I will show the results of our multi-dimensional hydrodynamic explosion models of PISNe, including results from the first-ever-published, three-dimensional model. The reliability of synthetic light curves, spectra, and chemical signatures used in the investigation of PISNe is tied directly to the accuracy of the nucleosynthetic products of our explosion simulations. For computational efficiency, our multi-dimensional explosion models use small nuclear reaction networks that may accurately capture the bulk properties of the explosion, but do not necessarily produce reliable chemical abundances. To solve this problem, we use the technique of particle post-processing using a large nuclear reaction network. I will show and discuss discrepancies between the chemical abundances produced in the outer ejecta of our explosion models and the abundances produced by post-processing, and the possible effects these may have on produced synthetic light curves, spectra, and chemical signatures of PISNe.

Speaker: Broxton Miles (North Carolina State University)

Abstract MilesetalAbstract.pdf

69 Detailed study of nuclear physics parameters via (p,gamma-reaction cross-section measurements

In order to understand and describe the astrophysical processes that are responsible for the nucleosynthesis of all different kinds of elements a precise knowledge of cross sections and reaction rates is necessary. However, in particular the network of the gamma-process, which plays an important role in the nucleosynthesis of the majority of the p nuclei, includes so many different reactions on - mainly unstable - nuclei, cross-section values are predominantly calculated in the scope of the Hauser-Feshbach statistical model. The calculated values depend heavily on the nuclear physics input-parameters like the nuclear level densities (NLD), the gamma-ray strength functions (gamma SF) and nucleon+nucleus optical model potentials (OMPs). Total and partial cross-section measurements can improve the accuracy of the theoretical calculations. To extend the experimental database, the 107Ag(p,gamma)108Cd reaction as well as the 93Nb(p,gamma)94Mo reaction were studied via the in-beam method at the high-efficiency HPGe gamma-ray spectrometer HORUS at the University of Cologne. Proton beams with energies close to the Gamow window were provided by the 10 MV FN-Tandem accelerator. The comparison of the experimental results to Hauser-Feshbach calculations allowed to find adjusted microscopic models for the NLD and gamma SF, which nicely reproduce the results of total and partial cross sections. Supported by the DFG (ZI 510/8-1) and the "ULDETIS" project within the UoC Excellence Initiative institutional strategy.

Speaker: Felix Heim (Institute for Nuclear Physics, University of Cologne)

Abstract 093_Heim.pdf

70 Determination of Nucleosynthesis Uncertainties with the PizBuin Monte Carlo Code: Production of p Nuclides in Thermonuclear Supernovae

The Monte Carlo (MC) framework PizBuin was developed to study nuclear uncertainties by postprocessing large reaction networks with trajectories obtained from a variety of nucleosynthesis sites. We perform large-scale MC variations using temperature-dependent rate uncertainties combining experimental and theoretical uncertainties. From detailed statistical analyses, realistic uncertainties on the final abundances are derived as probability density distributions. Furthermore, based on rate and abundance correlations an automated procedure to identify the most important reactions in complex flow patterns from superposition of many zones or tracers is used. This method is superior to visual inspection of flows and manual variation of limited rate sets. Here, we first present the general approach which already has been used to study uncertainties in the gamma process and the weak s-process in massive stars. Then we focus on new results concerning the application of PizBuin to the production of p nuclei in white dwarfs exploding as thermonuclear (type Ia) supernovae. (Further new results for the main s-process and the nu p process are presented elsewhere at this conference. The computationally very demanding study combined more than 4600 tracers to determine overall uncertainties originating from uncertainties in the nuclear input and the associated key reactions. Compared to the results we previously obtained for the gamma process in massive stars it is found that the uncertainties are smaller and fewer key reactions can be identified. This is due to the larger range of conditions encountered in thermonuclear supernovae, causing a multitude of possible flow patterns, avoiding bottlenecks and diminishing the impact of uncertainties in specific, isolated reaction rates. Despite of the fact that we used a particular 2D model of a white dwarf explosion, separately studying high density and low density regions allows to draw more general conclusions, also applicable to other explosion models. The relevance of these findings in the broader context of Galactic Chemical Evolution is briefly addressed. References T. Rauscher, N. Nishimura, R. Hirschi, G. Cescutti, A. StJ. Murphy, A. Heger, MNRAS {\bf 463} (2016) 4153. N. Nishimura, R. Hirschi, T. Rauscher, G. Cescutti, A. StJ. Murphy, MNRAS {\bf 469} (2017) 1752. G. Cescutti {et al.}, submitted to MNRAS. G. Cescutti {et al.}, this conference. N. Nishimura {et al.}, this conference. N. Nishimura, T. Rauscher, R. Hirschi, A. St.J. Murphy, G. Cescutti, C. Travaglio, MNRAS {\bf 474} (2018) 3133. C. Travaglio, T. Rauscher, A. Heger, M. Pignatari, C. West, Ap.\ J. {\bf 854} (2018) 18. C. Travaglio {et al.}, this conference.

Speaker: Thomas Rauscher (University of Basel &amp; University of Hertfordshire)

Abstract 143_Rauscher.pdf

71 Development of a supersonic jet target for the cross section measurement of 12C(alpha,gamma)16O with the recoil mass separator ERNA

Motivations beyond the ERNA upgrade with a focus on its new jet target development

Speaker: David Rapagnani (PG)

Abstract 133_Rapagnani.pdf

72 Development of a tracking detector to study the 12C(alpha,gamma)16O at astrophysical relevant energies

Stellar model calculations are extremely sensitive to the rate of 12C(alpha,gamma)16O. Although great efforts were devoted to decrease the uncertainty in the extrapolations, more precise data are needed to provide a good input to the stellar models. The available data indicate that its cross section at E0 = 300 keV is dominated by E1 and E2 radiative capture processes into the 16O ground state, where the main contribution to the capture cross section is given by two subthreshold states with Jpi = 1- and 2+ at Elevel = 7.12 and 6.92 MeV, respectively. Since the measurement of Dyer and Barnes in 1974 [1], the E1 and E2 contributions have been determined by measuring the gamma-rays in coincidence with 16O-recoils to reduce background. In one case [2] it was possible to measure the total cross section by the detection of recoils using the RMS (Recoil Mass Separator) ERNA (European Recoil mass separator for Nuclear Astrophysics). In the case of a RMS, an additional constrain to the gamma-ray data can be the measurement of the angular distribution of the recoils. Monte Carlo simulations together with the simulation of the beam transport through ERNA have shown that it could be possible to determine the E1 and E2 contributions by the analyses of the angular and time of flight distributions of the recoils at the end of the RMS. In order to achieve that, a two stage tracking detector is being developed. The first stage is a modification of the existing mirror detector [3]. The second stage is a parallel grid position sensitive detector that will be placed inside of the existing Ionization Chamber Telescope [4]. The detector development will be described and the expected physics outcome presented. [1] P. Dyer et al., Nuc. Phys. A 233(1974)495520. [2] D. Schrmann et al., Eur. Phys. J. A 26(2005)301. [3] A. Di Leva et al., NIM A 595(2008)381390. [4] D. Rogalla et al., NIM A 437(1999)266.

Speaker: Jeremias Garcia Duarte (INFN Napoli)

Abstract 135_GarciaDuarte.pdf

73 Direct capture cross section and low-energy resonances in the 22Ne(p,gamma)23Na reaction

The 22Ne(p,gamma)23Na reaction takes part in the neon-sodium cycle of hydrogen burning and may affect the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying non-resonant component. Three new resonances at Ep = 156.2, 189.5, and 259.7 keV, respectively, have recently been observed and confirmed. However, significant uncertainty remains due to the off-resonant process and two hypothetical resonances at Ep = 71 and 105 keV, respectively. Here, new data with unprecedented high luminosity and low background on these aspects of the 22Ne(p,gamma)Na reaction are reported. Stringent upper limits are placed on the two hypothetical resonances, ruling them out for astrophysical purposes. The off-resonant yield has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. The 22Ne(p,gamma)23Na reaction rate, which used to be the most uncertain rate of the neon-sodium cycle, is now the best known rate.

Speaker: Federico Ferraro (Genova University & INFN)

Abstract 121_Ferraro.pdf

74 Direct measurement of the 13C(α,n)16O reaction at LUNA

13C(α, n)16O reaction is the main neutron source of the s process, which is responsible for the synthesis of about half of the heavy (A> 58) nuclei in the universe. This process takes place in the interiors of low mass AGB stars, with temperatures between 90 and 100 MK, corresponding to Gamow energies in the range of 140 and 230 keV. The direct measurement of the 13C(α,n)16O reaction cross section towards the rele- vant energy range for astrophysics is the aim of a current experimental campaign of the LUNA experiment. The low background condition in the LNGS deep underground laboratory, combined with the LUNA accelerator offers a unique possibility to suppress the natural neutron background that has so far been the limiting factor of direct measurements on the surface. Another important source of systematic uncertainty comes from the target degrada- tion during the beam irradiation. In the poster I will present the current status of the project, focusing the work on the analysis for the monitoring of the target degradation and the status of data analysis.

Speaker: Giovanni Francesco Ciani (Gran Sasso Science Institute)

Abstract 58_CianiGiovanniFrancesco.pdf

75 Electron capture processes in ONe cores

In intermediate-mass stars (∼8–10 solar masses), carbon burning results in degenerate cores composed mostly out of oxygen and neon (ONe cores). Lighter stars in this mass range will shed their stellar envelopes and end as ONe white dwarfs. For heavier stars, the ONe cores will keep accumulating mass from the surrounding carbon-burning shell. The ultimate fate of this latter evolutionary path is still uncertain. A crucial role is played by electron capture reactions that are triggered as the core contracts (see e.g. [1,2]). These reactions do not only reduce the degeneracy pressure by removing electrons, but can also heat and cool the core in the form of double electron capture and Urca processes, respectively. The electron capture on Ne20 releases enough heat to ignite runaway oxygen burning. This scenario is called an electron-capture supernova and leads to either a collapse to a neutron star or a thermonuclear explosion, disrupting the star. The exact outcome is very sensitive to the density at oxygen ignition [3], meaning that the evolution up to this point must be studied carefully. Following carbon burning, the main content of the core is O16, Ne20, Na23, Mg24 and Mg25. In this contribution we will discuss the possible impact of electron capture processes on additional nuclei, for example those inherited from a non-zero metallicity of the progenitor. Excluding such effects would mean that the nuclear physics of degenerate ONe cores would be almost completely determined by experimental data. This work is supported by the Deutsche Forschungsgemeinschaft through contract SFB 1245. References [1] J.Schwab et al., Mon.Not.Roy.Astron.Soc. 453(2)(2015)1910–1927. [2] J.Schwab et al., Mon.Not.Roy.Astron.Soc. 472(3)(2017)3390–3406. [3] S.Jones et al., Astron.Astrophys. 593(2016)A72.

Speaker: Dag Fahlin Strömberg (Technische Universität Darmstadt)

Abstract 180_stroemberg.pdf

76 Estimating the Neutrino Flux from X-ray Bursts

Type I X-ray bursts are thermonuclear explosions on the surface of accreting neutron stars in low-mass X-ray binaries. They are highly energetic (sim 10^38 erg) events and so can release energy in the form of neutrinos. The neutrino flux released during an X-ray burst comes primarily from beta-decays. Using KEPLER, a 1D implicit hydrodynamics code that calculates the full nuclear reaction network, we have measured the neutrino fluxes of type I bursts for a range of initial conditions. We find that neutrino losses are between 6 times10^-5 (low hydrogen fraction) and 0.185 (high hydrogen fraction), of the total energy per nucleon, Qnuc. We also find a dependence on the neutrino flux with metallicity of the accreted fuel. Recent literature often uses the approximation formula Qnuc=1.6+4 Xb,mathrmMeV/mathrm{nucleon} where Xb is the average hydrogen mass fraction of the ignition column to estimate Qnuc and hence fuel composition. We find this expression is a very poor fit (rms = 0.4..) to the KEPLER predictions. We attribute the discrepancy to the assumption of 35% energy loss due to neutrinos during the rp and alpha p processes in this expression, however, it is only at beta-decays that sim35 of energy is lost due to neutrino emission, and beta-decays do not contribute much to the total energy. Using total measured burst energies from KEPLER for a range of initial conditions, we have determined a new approximation formula, Qnuc=0.93+7.41bar-1.88\barX^2, with a root mean square error (RMS) value of 0.07 MeV/nucleon, compared to the old relation that has an RMS value of 0.47 MeV/nucleon.

Speaker: Adelle Goodwin (Monash University)

Abstract Goodwin_NIC_abstract_2018-3.pdf

77 Explosion of fast spinning sub-Chandrasekhar mass white dwarfs

We study the explosion of rotating sub-Chandrasekhar mass white dwarfs using three-dimensional hydrodynamic simulations. High rotational speeds are assumed in order to significantly distort the initial spherical geometry of the white dwarf. Unlike spherically symmetric models, when He-ignition is located far from the spinning axis the detonation wave trains arrive asynchronously to the antipodes. Models considering different masses of the He-shell, He-ignition locations and rotational velocities, assuming rigid rotation in all cases, are analyzed. We study independently both, the detonation of the He-shell, artificially avoiding carbon-ignition, and the complete detonation of the white dwarf. The spontaneous detonation of the carbon-oxygen core is obtained in all calculated models. The explosion energies and nucleosynthesis match the basic observational constraints of Type Ia Supernovae, confirming the viability of the Double Detonation mechanism when the white dwarf is spinning fast.

Speaker: Inma Dominguez (Universidad de Granada)

Abstract 152_Dominguez.pdf

78 Explosive nucleosynthesis in aspherical supernovae of massive stars with the solar and zero metallicity

We have investigated explosive nucleosynthesis in core-collapse supernovae (SNe) of massive stars, based on two-dimensional (2D) hydrodynamic simulations of the SN explosion. Employing a simplified light-bulb scheme for neutrino transport and excising a central part of a proto-neutron star (PNS), we follow long-term evolution of the SN explosion over 1.0 second after the core bounce for 22 massive stars with masses from 10.8 to 40M and with the solar metallicity and 15 stars with masses from 10 to 40M and with zero metallicity, adopting a PNS core model, with which we evaluate evolution of neutrino luminosities and temperatures as in Ugliano et al. 2012. We adopt two parameter sets of the PNS core model; one results in faster explosion of 0.2-0.4s after the bounce and the other later explosion of 0.4-0.6. Then, we calculate abundance evolution of the SN ejecta through post-processing calculation using a large nuclear reaction network including 463 nuclei from neutron, proton to Kr and evaluate abundances and masses of the SN ejecta. We find two explosion models of 19.4 and 25.0 M_ stars Z=Z_ whose E and MnucNi56 and MnuNi57 are comparable to those observed in SN1987A, only for the PNS core model with the faster explosion. For the progenitors with Z=Z_ and using the PNS core model with the faster explosion, we well reproduces a correlation between MnucNi56 and E_rm observed in Type II-Plateau SNe (Pejcha and Prieto, 2015). Moreover, we have calculated IMF-averaged abundances of the SN ejecta of the Z=Z progenitors and added appropriate amounts of ejecta from Type Ia SN (W7 model of Iwamoto et al. 1999 and 20% of all SNe) to the IMF-averaged abundances. The resultant abundances are found to be well agree with those in the solar system. Finally, we have calculated IMF-averaged abundances of the SN ejecta of progenitors with Z=0 and find that the IMF-averaged abundances well reproduce averaged abundances of observed in metal-poor stars (Cayrel et al. 2004).

Speaker: Shin-ichiro Fujimoto (National Institute of Technology Japan)

Abstract 123_Fujimoto.pdf

79 First radiative proton capture cross-section measurements on 107,109-Ag and 112-Cd relevant to the p-process

One of the important, but still unsettled topics in Nuclear Astrophysics is the production of the p-nuclei [1,2]. The p-process relies on an extended reaction network, which can be described theoretically by the Hauser-Feshbach statistical model, which in turn relies strongly on experimental data. To provide reliable data for p-nuclei, an experimental campaign at the Tandem Accelerator Laboratory of NCSR ``Demokritos'', focusing on measurements of cross-sections in the 107,109-Ag(p,γ)108,110-Cd [3] and 112-Cd(p,γ)113-In [4] reactions was carried out. Both reactions were studied using a set of four HPGe detectors via the in-beam γ-ray spectroscopy, while for the latter the activation method was additionally employed to account for the population of a low-lying isomeric state. Total cross sections for proton beam energies lying inside the Gamow window for energies relevant to p-process nucleosynthesis were obtained for the first time. Experimental results are compared to Hauser-Feshbach calculations performed with the latest version of the TALYS code (v1.9) [5]. An overall good agreement has been achieved. These results provide important new input for the theoretical description of the p-process, but additionally for the origin of the cross-point p-nucleus 113-In. References [1] M. Arnould and S. Goriely, Phys. Rep. 384, 1 (2003) [2] T. Rauscher et al., Rep. Prog. Phys. 76, 066201 (2013) [3] A. Khaliel et al., Phys. Rev. C 96, 035806 (2017) [4] A. Psaltis et al. (2018), in prep. [5] A. Koning, S. Hilaire and S. Goriely, TALYS-1.9, A Nuclear Reaction Program, NRG-1755 ZG Petten, The Netherlands (2017)

Speaker: Athanasios Psaltis (McMaster University)

Abstract 35_PsaltisAthanasios.pdf

80 First Results from the CASPAR Underground Nuclear Astrophysics Facility

In the ongoing drive to extend the lower-energy limits of cross-section measurements in nuclear astrophysics, new techniques and facilities are required to enter or even approach the burning regime of interest for many astrophysically significant processes. Many unique approaches have been developed to overcome or navigate around the exponentially decreasing reaction probability at low energy extremes. As current laboratory experiments fight to reach this stellar burning window, the rapid reaction decrease drives the need for higher intensity accelerators, more robust and isotopically enriched target material and lower background interference. The natural background suppression of underground accelerator facilities enables the extension of current experimental data to the lower energies needed. New facilities around the world are coming on-line with a view to capitalizing on underground cosmic-ray suppression, each offering their own unique techniques and capabilities. CASPAR is the first underground nuclear astrophysics laboratory in the United States and first measurements and results will be given.

Speaker: Daniel Robertson (University of Notre Dame)

Abstract 106_Robertson.pdf

81 First results of the high-current, high-stability 3.5 MeV Singletron™ for LUNA-MV

HVE has designed and built a dedicated 3.5 MV linear single-ended DC accelerator (Singletron) to satisfy the stringent demands of the LUNA MV project at LNGS (L’Aquila, Italy), in which nucleosynthesis is studied in the final Helium and Carbon burning stages that lead to the generation of heavy elements. The beam current capability of the system include e.g. 1000 μA H+, 500 μA 4He+ (both 500 keV - 3.5 MeV) and 100 μA 12C2+ (1.0 - 7.0 MeV). Beam energy stability and ripple are in the order of 1.10-5 and energy reproducibility is ~1.10-4. The system is equipped with a 10 GHz, all permanent magnet ECR ion source for high current at higher charge states and to have long servicing interval, specified at 700 hrs (at max intensity) , but anticipated to be much longer. In this contribution will introduce the system with its design details and will show the first results obtained.

Speaker: Mous Dirk (High Voltage Engineering Europa)

Abstract 159-Mous.pdf

82 First time measurement of the 19F(p, α1)16O reaction at astrophysical energies: evidence of resonances through the application of the Trojan Horse Method

The 19F(p,α)16O reaction is an important channel of fluorine destruction in H-rich environments as the outer layers of asymptotic giant branch (AGB) stars. Measurements of the 19F(p,α)16O reaction via the Trojan Horse Method (THM) have shown the presence of resonant structures not observed before [1,2,3]. As a consequence, the reaction rate at astrophysical temperatures (about 10^7−10^8 K) exceeds up to a factor of 1.7 the one given in [4]. This fact might have important consequences for stellar nucleosynthesis, helping to solve the gap between the F aboundances predicted by theoretical models for AGB stars and the observed values [5]. Here we present the result of an experiment in which THM was used to extract the quasi-free contribution of the 2H(19F,α16O)n reaction to 19F(p,α1)16O channel, corresponding to the population of the first excited state of the 16O. Despite the low statistics, three resonances in the Ecm energy region below about 500 Kev have been observed. This result confirms the findings of the previuos experiments focused on the 19F(p,α0)16O channel and hints again to an enhancement of the 19F(p,α)16O destruction rate, with respect to what presently predicted.

Speaker: Bernardo Becherini (Perugia University)

Abstract 103_Becherini.pdf

83 From the cosmological lithium problem to the Galactic lithium evolution

Lithium is widely used as a tester to the cosmological model, a probe of stellar structure, and an age indicator of young stellar clusters. It is the very element that presents deep insights yet many problems to astrophysics. I will first introduce a stellar solution to the cosmological Li problem, which reveals that Li was first destroyed and re-accumulated by these stars shortly after they were born, then discuss the different Li enrichment histories in the Galactic thick and thin discs. The newly-found Li decline for super-solar metallicity stars will also be discussed. if this decline is real, Li would be the first element we know whose absolute abundance declines with metallicity.

Speaker: Xiaoting Fu (University of Bologna & INAF - OAS)

Abstract FU_abstractNIC2018.pdf

84 Gamow-Teller Excitations in Open-Shell Nuclei at Finite Temperatures

Spin-isospin excitations are known as fundamental modes of excitation in nuclei that gained considerable attention with the advances in experimental facilities and progress in theoretical models. The detailed knowledge about their structure is important, not only for nuclear physics but also for the nuclear astrophysics. Especially, in the calculation of nuclear weak interaction processes (beta decay, electron capture, neutrino-nucleus scattering etc.), accurate knowledge on the spin-isospin excitations is necessary. The proton-neutron quasiparticle random phase approximation (PNQRPA) based on the relativistic energy density functionals provides a consistent and reliable approach for the description of the spin-isospin excitations over the nuclide map. On the other hand, it is known that the nuclear weak interaction processes in stellar environments mainly take place at finite temperatures ranging from several hundreds of keV to MeV. Recently, the effect of the temperature on the electron capture cross sections and rates was studied with the finite temperature proton-neutron random phase approximation, using the relativistic and non-relativistic functionals. However, the calculations were limited because the pairing correlations were not taken into account. Therefore, for a complete understanding of the nuclear weak interaction processes at finite temperatures, it is necessary to extend the current theoretical models to include both the temperature and pairing effects in the calculations of the spin-isospin excitations for open-shell nuclei. In this work, we established the finite temperature proton-neutron QRPA based on the relativistic nuclear energy density functional with density dependent meson-nucleon couplings, and pairing correlations are taken into account in the BCS scheme. Within this framework, we have performed calculations for the Gamow-Teller excitations in open-shell nuclei using the DD-ME2 functional. The effect of the temperature on the strength functions and excitation energies of the Gamow-Teller excitations is investigated for the selected open-shell nuclei. In addition, the interplay between the temperature and pairing effects is discussed at low temperatures, where both effects are relevant.

Speaker: Esra Yuksel (University of Zagreb & Yildiz Technical University)

Abstract NIC2018_Yuksel.pdf

85 GASTLY: a new apparatus for detection of low-energy light charged-particles in nuclear astrophysics experiments

A new detection array called GASTLY (GAs-Silicon Two-Layer sYstem) has been designed to detect and identify low-energy light charged-particles (p,d,alpha,...) emitted in nuclear reactions of astrophysical interest. Devoted to the measurement of nano-barn cross-sections, the system is optimised for large solid angle coverage and for low-energy detection thresholds. The array consists of eight modules, each comprising an ionisation chamber (IC) and a large area silicon strip detector (SSD), both housed in an aluminium pyramidal case, and providing the DE-E information used for particle identi1cation. The IC key components are an entrance window (2.6 um thick Havar foil) acting as a cathode, a Frisch grid (gold-coated tungsten wires having 20 um diameter and 3 mm pitch size), an anode (1.5 um thick Mylar foil, metallised with 50 ug/cm2 of aluminium) and a serie of 25 guard rings surrounding the IC active region and ensuring the uniformity of the electric field. The IC is operated with CF4 gas, flowing (0.1-1.0 litres/h) and maintained at a constant pressure (300 mbar max) and the length of the active region is of 116 mm. The SSD is about 58x58 mm2 large and 300 um thick and its front face is segmented in 16 strips (3.5x58.0 mm2 each), while the conductive back plane is unsegmented. The readout electronics, mainly consisting in home-made low-noise charge preamplifiers (plus a 16-channel ASIC chip, when the individual strip analysis is required), is also placed inside the pyramid, near and behind the detectors, to reduce the environmental electromagnetic noise. The distance between the target and the entrance window of the GASTLY modules is of 54 mm (74 mm for two modules) and a total solid angle of about 0.7 sr is subtended by the whole apparatus. The angular uncertainty Dtheta, for angular distribution measurements, due to the width of the strips and to their rectangular shape, is of about 1.0°-1.5°. We will report on the performance of the GASTLY array as obtained during its commissioning phase with standard alpha-particle sources and during in-beam tests with an intense 12C beam. Typical energy resolutions DE(FWHM)/E of about 3% and 2% were obtained for the IC and the SSD, respectively. The GASTLY modularity and versatility allow for use in a variety of experiments and the apparatus is presently installed at the Centre for Isotopic Research on the Cultural and Environmental heritage (CIRCE) of the Università della Campania “L. Vanvitelli” (Caserta, Italy) for the study of one of the most important reactions in nuclear astrophysics, namely the fusion of two 12C nuclei known as carbon burning. At characteristic temperatures of 0.3 - 1.9 GK, corresponding to interaction energies Ecm = 1.0 - 3.5 MeV, carbon fusion proceeds through two main channels: 12C(12C,p)23Na (Q-value = 2.24 MeV) and 12C(12C,alpha)20Ne (Q-value = 4.62 MeV) and a number of excited states in the residual nuclei can be populated, leading to ejected proton- and alpha-particle energies up to a few MeV, depending on beam energy and detection angle. The GASTLY features successfully allowed the contemporary detection and identi1cation of protons and alpha-particles emitted in such reactions.

Speakers: Elia Lizeth Morales Gallegos (NA), Mauro Romoli (NA)

Abstract 196-Romoli.pdf

86 Germanium-detector based study of the 2 H(p,gamma)3He cross section at LUNA

Recent, precise measurements of the primordial 2 H abundance [1] have opened thepossibility to precisely determine of the primordial baryon-to-photon ratio, independent from the cosmic microwave background. For their interpretation, the 2 H abundance data require equally precise nuclear data, in particular on the 2 H(p, γ) 3 He reaction. Deep underground in the Gran Sasso laboratory, Italy, the LUNA collaboration is undertaking a dedicated effort to measure the 2 H(p,γ)3He cross section directly in the Big Bang energy window of interest. The campaign is divided in two phases based on a BGO and a high-purity germanium (HPGe) detector, respectively. The present poster will report on the second, HPGe-based phase of the experiment. Due to the Doppler shift of the emitted γ-rays, in addition to the absolute yield also information on the γ-ray angular distribution, thus reducing the systematic uncertainty. The characterization and calibration of the setup and detectors, background conditions, and potential sources of uncertainty will be discussed.

Speaker: Klaus Stoeckel (HZDR)

Abstract 148-Stoeckel.pdf

87 H-He Shell Interactions and Nucleosynthesis in Massive Population III Stars

Interactions between H- and He-shell convection layers have been seen in 1D stellar models of massive Pop III stars \cite{WW,LC} but until recently have not been investigated in detail. Using the 1D stellar evolution code \texttt{MESA}, we find that when this event occurs in a 45 \,\mathrm{M_Pop III model, it leads to H-burning luminosities of $\mathrm{\log L_HL_sim13$ due to convective-reactive mixing at the interface between the two shells. These conditions render 1D models unreliable and we will report on initial results of our new project to investigate the hydrodynamic nature of mixing at the interface between the H- and He-convection zone (Fig.\,1). This mixing is similar to H-ingestion events found in other environments, such as He-shell flashes in low-mass stars \cite{FH1,FH2} and may lead to the \textit{i}-process with neutron densities of $\approx 10^{13} \mathrm{cm}^{-3}$, reproducing the nucleosynthetic abundance patterns (Fig.\,2) existing in some of the most metal-poor stars \cite{PopIII-ip}. We have now also investigated in more detail the conditions for Ca production in Pop III stars, and specifically the role of the 19\mathrm{F}(p,\gamma)^{20}\mathrm{Ne}$ reaction. Using default rates, we find that unless mixing between H-and He layers is involved Ca is produced at a level at least a factor 10 below the value observed in the most Fe-poor star.

Speaker: Ondrea Clarkson (University of Victoria)

Abstract 136_Clarkson.pdf

88 Heavy puzzle pieces: Learning about the i process from Pb abundances

The large majority of elements heavier than iron are formed by the slow (s) and rapid (r) neutron capture processes. However, it has become clear that a neutron capture process operating at neutron densities intermediate to the s and r process (i process) gives rise to its own characteristic abundance pattern. This i-process pattern is successful at reproducing observed heavy-element abundances that could not be explained previously, e.g. those of carbon-enhanced metal-poor stars that show enrichments of s- and r-process elements (CEMP-s/r). The required high neutron densities may occur in the thermal pulses of Asymptotic Giant Branch (AGB) stars as a result of proton ingestion episodes. However, the sites of the i process are as yet unknown. Comparing theoretical predictions of i-process nucleosynthesis with the observed abundance patterns of CEMP stars and post-AGB stars in the Magellanic Clouds allows us to learn about the thermodynamic properties of possible i-process sites. In particular the Pb abundances may hold the key to solving this mystery because this is one element that is predicted to be significantly enhanced by the s process at low metallicities, in contrast to observations of post-AGB stars which only show low to moderate Pb enhancements. In this talk I will present the results of nuclear-network calculations of i-process nucleosynthesis in comparison to observations.

Speaker: Melanie Hampel (Monash University)

Abstract Hampel_abstractNIC2018.pdf

89 Impacts of nuclear-physics uncertainty on nup-process nucleosynthesis

We evaluated the uncertainty relevant to nup-process nucleosynthesis using a Monte-Carlo centred approach. Based on a realistic and general prescription of temperature dependent uncertainty, we have examined the impact on the nup-process in several physical parameters of astrophysical models. We calculated the total uncertainty of final abundances caused by nuclear-physics inputs and identified key reactions that have significant impacts on the nucleosynthesis products. In the presentation, we will suggest the priority list of nuclear reactions to be investigated in future experiments and/or calculations.

Speaker: Nobuya Nishimura (YITP, Kyoto University)

Abstract 200-Nishinura.pdf

90 Improving nuclear data input for r-process calculations around A~80

The distribution of solar system elemental abundances, after correction for s-process contributions, shows a maximum around A ∼ 80 sometimes called the 1 st r-process abundance peak. However the origin of the elements contributing to this peak is uncertain and several astrophysical processes have been proposed. Observations in ancient ultra metal poor stars [1] indicate that other mechanisms contribute here and may be even dominant [2]. We consider here a weak r-process [3], which can occur in core-collapse supernova events [4] or neutron star mergers [5]. Sensitivity studies [6] indicate the need to measure half-lives T_1/2 and neutron emission probabilities Pn for neutron-rich nuclei in this region, as the prediction of different theoretical alculations disagree significantly, and these quantities shape the final abundance distributions. The BRIKEN project was launched to expand our knowledge on T 1/2 and P n values to not-yet-accessed very neutron-rich nuclei over the entire nuclear chart, that are important for r-process abundance calculations. It exploits the very large beam intensities of the RIBF facility at RIKEN [7] and the selection capability of the BigRIPS in-flight separator [8] adding new advanced state-of-the-art instrumentation. We will report about the experiment performed in June 2017 aiming at the A ∼ 80 region, where the BRIKEN neutron counter [10] was combined with the AIDA implant and decay detector [9]. Some preliminary results for T 1/2 and P n values will be presented and compared with theoretical calculations. Their impact on calculated abundances will be explored. References [1] C. Sneden et al., Ann. Rev. Astron. Astroph. 46, 24 (2008). [2] C.J. Hansen et al., Astroph. J. 797, 123 (2014). [3] R. Surman et al., AIP Advances 4, 041008 (2014). [4] S. Wanajo, Astroph. J. Lett. 770, L22 (213). [5] A. Perego et al., Month. Not. Roy. Astron. Soc. 443, 3134 (2014) [6] T. Shafer et al., Phys. Rev. C 893, 055802 (2016). [7] H. Okunoet al., Prog. Theor. Exp. Phys. 2012, 03C002 (2012). [8] T. Kubo et al., Prog. Theor. Exp. Phys. 2012, 03C003 (2012). [9] T. Davinson et al., http://www2.ph.ed.ac.uk/ td/AIDA/ [10] A. Tarifeo-Saldivia et al., J. Instrum. 12, 04006 (2017).

Speaker: Alvaro Tolosa Delgado (IFIC (Instituto de Fisica Corpuscular))

Abstract 147-Tolosa-Delgado.pdf

91 Indirect (n,gamma)91,92Zr Cross Section Measurements for the s-Process

The playground for the nucleosynthesis is found in the interior of stars and/or in extreme cosmic events. The major contributors to creating heavier elements are the neutron capture processes. The key question for these processes is whether the nuclear system after neutron absorption will keep the neutron and emitting gamma rays to dissipate the energy, or will it eject the neutron or other particles/fragments and thereby producing other elements? For the s-process, this question is important at the so-called branch points, where the beta-decay rate is comparable with the (n,gamma) rate. Nuclear level densities (NLDs) and gamma-ray strength functions (gammaSFs) are essential quantities in the determination of the (n,gamma) rates. At the Oslo cyclotron laboratory, we have used the 92Zr(p,p gamma)92Zr and 92Zrp,d gamma)91Zr reactions to extract NLDs and gammaSFs using the Oslo method. These 91,92Zr gammaSF data, combined with photonuclear cross sections, cover the whole energy range from E_gamma~1.5MeV up to the giant dipole resonance at E_gamma~17MeV. The wide-range gammaSF data display structures at E_gamma~9.5MeV, compatible with a superposition of the spin-flip M1 resonance and a pygmy E1 resonance. Furthermore, the gammaSF shows a minimum at E_gamma~2-3 MeV and an increase at lower gamma-ray energies, known as.... The experimentally constrained NLDs and gammaSFs are shown to reproduce known (n,gamma) and Maxwellian-averaged cross sections for 91,92Zr using the reaction code, thus serving as a benchmark for this indirect method of estimating (n,gamma) cross sections for Zr isotopes. References E.M.Burbidge, et al., Rev. Mod. Phys. {\bf 29}, 547 (1957). M.Guttormsen, et al., Phys. Rev. C {\bf 96}, 024313 (2017). H.Utsunomiya, et al., Phys. Rev. Lett. {\bf 100}, 162502 (2008).

Speaker: Magne Guttormsen (University of Oslo)

Abstract 53_GuttormsenMagne.pdf

92 Influence of variations in the astrophysical conditions and alpha,mathrm{n} reaction rate uncertainties on the nucleosynthesis in neutrino-driven supernova ejecta

Despite the rapid progress in supernova simulations and experimental nuclear astrophysics the astrophysical and nuclear physics uncertainties are still large and critically affect the nucleosynthesis. Thus, we address both sources of uncertainty and investigate their influence on the nucleosynthesis in neutron-rich neutrino-driven supernova ejecta. Our systematic study of the astrophysical conditions relies on steady-state models due to the high computational costs of hydrodynamic simulations. We present different abundance patterns which can be synthesized in neutron-rich supernova ejecta and give an overview of the potential nucleosynthesis evolution in supernova simulations \cite{Bliss2018}. Based on the survey of the astrophysical conditions we study the impact of the nuclear physics uncertainties on the nucleosynthesis with our main focus on the (\alpha,mathrm{n}) reactions. (alpha,mathrm{n}) reactions are essential to redistribute matter and to reach heavier nuclei in neutron-rich ejecta. Their uncertainties arise from the statistical model and its nuclear physics input \cite{Pereira2016}. We present the results of our Monte Carlo sensitivity study to identify individual critical reactions. The reduction of the uncertainties in these reactions will significantly decrease the influence of nuclear physics uncertainties. Since the nucleosynthesis path evolves close to stability, the critical reactions can be measured with new radioactive beam facilities like FRIB or FAIR in the near future.

Speaker: Julia Bliss (TU Darmstadt)

Abstract 176-Bliss.pdf

93 Inhomogeneity Primordial Magnetic Field, non Maxwell-Boltzmann Distribution of Ions, and their Effect on Big Bang Nucleosynthesis

Cosmological theory of Big Bang nucleosynthesis (BBN) predicts the right amount of production of the light elements 2H, 3He, 4He, and 7Li in the early universe to constrain several cosmological parameters. We find that the abundance of these elements can be affected strongly by a stochas- tic primordial magnetic field (PMF) whose strength is spatially inhomogeneous. We assume a large-scale stochastic PMF with a power law (PL) correlation function and strength that follows a Gaussian distribution, while the total energy density is uniform. We show that the distribution function of particles deviates from the Maxwell-Boltzmann (MB) distribution with the stochastic PMF fluctuations being taken into account. This deviation is related to ρλ and σ which are scale invariant (SI) strength of PMF energy density and fluctuation parameter. We perform a BBN network calculation by taking account of non-MB distribution generated by PMF strength distri- bution, and show the elemental abundances as a function of baryon to photon ratio η, ρλ, and σ. We then concluded that the fluctuation of PMF strength reduces 7Be production and enhances 2H production. We analyze thermonuclear reaction rates compared with classical MB framework, find that the charged particles reaction rates are very different from each other due to the Coulomb penetration effects. On the other hand, neutron induced reaction rates almost maintain the same amplitudes as those in the MB distribution. We also show that the distribution function in our PMF model indicates a linear drift with a relatively steeper sloop than the MB distribution in terms of Fokker-Plank equation. Finally, we constrain the parameters ρλ and σ for our fluctuated PMF model from observed abundances of 4He and 2H. In this model, 7Li abundance is significantly reduced within an allowed region from observational constraints.

Speaker: Yudong Luo (University of Tokyo)

Abstract 6_LuoYudong.pdf

94 Isomeric RIB Production of Aluminum-26

26mathrmAl is known as the first specific radioactivity detected via characteristic beta-delayed gamma-ray by astronomical telescopes. Despite a lot of effort over the past three decades, the particular production sites of galactic 26Al are not well understood and there is a discrepancy between observations and theories on estimated abundance of 26mathrmAl in the interstellar medium. Its isomer, 26Al, which is $Jpi=0+ and has a short lifetime of 6.35~s compared with the ground state, 26gAl, which is Jpi=5+ and T_{1/2}=0.72~Myr, may play an important role to the problem because it falls to 26Mg as super allowed Fermi transition and does not emit any gamma-rays. The two states, 26g,Al, are suggested to be in transition and in thermal equilibrium by thermal photons via low-lying 1+ state, at least in extremely high temperature environments, such as a supernova. However the experimental information on the isomer is poorly examined and thus was requested for further experimental study by stellar modelers. The RI beam production of 26mAl is a step to approach the puzzles of the abundance under the equilibrium. We will present an overview of the experiment to produce the isomeric RI beam of 2Al and measure proton elastic resonant scattering with a thick target in inverse kinematics by using the Center for Nuclear Study low-energy radioactive ion beam separator (CRIB), located at RIKEN Nishina Center.

Speaker: Shimizu Hideki (Center for Nuclear Study, the University of Tokyo)

Abstract 158_Shimizu.pdf

95 Measurement of the 16O(n, alpha)13C reaction cross-section at the CERN n_TOF facility

The fundamental role played by the 13 C(alpha,n)16O reaction rate in the understanding of stellar nucleosynthesis processes is widely recognized. Heavy elements (90 < A < 204) are produced in light Asymptotic Giant Branch (AGB) stars, with masses M/M_sun< 3, by the slow neutron capture process (s-process), which main source of neutrons is precisely the 13C(alpha,n)16O reaction. Therefore, an accurate and precise knowledge of this reacion rate is crucial to correctly model the nucleosynthesis process and to predict the abundances of elements along the s-process chain. A direct measurement is experimentally extremely challenging to perform. In this context, an indirect method to obtain this cross section is chosen to measure the inverse 16O(n,alpha)13C reaction and apply the time-reversal invariance theorem. To this purpose, a Double Frisch Grid Ionization Chamber (DFGIC) containing the oxygen atoms as a component in the counting gas has been developed and a prototype was constructed at Helmholtz-Zentrum Dresden-Rossendorf, in Germany. The first inbeam test of the detector has been performed at the first experimental area (EAR1) of the neutron time-of-flight facility (n_TOF) at CERN. The neutron beam is produced by spallation of 20 GeV/c protons from the CERN Proton Synchrotron accelerator on a water-cooled lead target coupled with a moderation system. This, together with the 185 m flight path allow to reach a very good energy resolution and an instantaneous high neutron flux, which are key features to successfully measure the 16O(n,alpha)13C reaction cross-section. The outcome of the detector test will be presented, with a particular focus on the performance of the detector and electronics in the high-energy region of the neutron spectrum, which is of main interest because of the reaction threshold of 2.35 MeV. In addition, the future developments will be illustrated, which will lead to the final measurement by the end of 2018.

Speaker: Sebastian Urlass (CERN)

Abstract 74_UrlassSebastian.pdf

96 Measurement of the 3He(a,g)7Be gamma-ray angular distribution

The 3He(a,g)7Be reaction affects the nucleosynthesis of 7Li as well as the predicted solar 7Be and 8B neutrino fluxes. It is being studied over a wide energy range at the Rossendorf 3 MV Tandetron accelerator, with a focus on the measurement of the gamma-ray angular distribution at E=1 MeV. There are multiple and overlapping precise experimental data sets at E=0.7-1.3 MeV. Any extrapolation of this precise data down to a unique data set from an experiment of the LUNA collaboration at E=0.09-0.13 MeV has to deal with the fact that at E=1 MeV, the capture is possible both from s-wave incident particles and from d-wave incident particles, whereas at 0.1 MeV and lower the d-wave component plays no role due to the angular momentum barrier. A measurement of the angular distribution of the emitted gamma-rays at E=1 MeV may constrain the relative contributions of s-wave and d-wave components at high energies and thus enable a better comparison between the high-energy and the low-energy data points. Data from a first run for the angular distribution of the emitted prompt gamma-rays in the 3He(a,g)7Be reaction was done using a setup of four HPGe detectors at various angles and shall be presented here.

Speaker: Steffen Turkat (IKTP, TU Dresden)

Abstract 72_TurkatSteffen.pdf

97 Measurement of Γ partial widths from carbon-12 excited states using CHIMERA

Measuring very small partial widths of carbon-12 from the Hoyle and the 9.6 MeV states above the particle emission threshold are of astrophysical interest because only after such decay carbon-12 is formed after a triple alpha process [1]. In the reaction α+ 12 C → α+( 12 C^∗ +γ) we used a multi-particle coincidence technique, developed with 4π multi-detector CHIMERA, in order to suppress the gamma background [2]. The CHIMERA data acquisition system for CsI was updated using the GET [3] digital electronics. Details of the suppression method and first results of the analysis will be presented. References [1] F.Herwig, S.M. Austin and J.C. Lattanzio Phys. Rev. C 73 (2006) 025802. [2] Giuseppe Cardella small Γ_γ et al. A new method for the determination of very partial widths. 2017:EPJ Web Conf. [3] E.C. Pollacco et al. NIMA Volume 887, 11 April 2018, Pages 81-93.

Speaker: Jose Francisco Favela Perez (INFN Catania)

Abstract 105_FavelaPerez.pdf

98 Measurements of Iron Meteorites 60Ni/58Ni by means of MC-ICP-MS: Procedure development and performances characterization at CIRCE Lab

Isotope fingerprints represents an attractive target for examining the nucleosynthetic origins of Solar System material, relating differentiated and primitive meteorite types, and studying mixing processes in the early solar nebula. Among the others chemical elements, Nickel is a moderately refractory and siderophile element, and also a major component of both iron and silicate meteorites, hence representing an attractive tar- get for cosmochemistry studies [1]. 60Ni isotope variations can therefore potentially be used to date nebula events. Likewise, 60Fe is believed to be synthesised in a high temperature stellar environment and not within the Solar System [2]. The presence of live 60Fe inferred from Ni isotope compositions represents a diagnostic fingerprint of material created in a nearby stellar explosion that was subsequently transported to the nascent solar nebula more than 10 Ma. The initial abundance of 60Fe, relative to other short-lived nuclides, can fill some important gaps placing important constraints on the nucleosynthetic processes responsible for creating these nuclides. In this field of re- search MC-ICP (Multi Collector-Ion Coupled Plasma) mass spectrometry represents the ideal mas spectrometry methodology capable to guarantee: i) the necessary sensitivity (i.e. ε60Ni=.03) to detect small 60Ni enrichments; ii) a low time consuming chemistry (i.e. mostly based upon ion exchange chromatog- raphy); iii) an overall high ionization efficiency onto the isotopic species to be anlysed; iv) a high mass sensitivity allowing for isobar separation and/or correction. This paper presents complete method development (i.e based on [3] and and proce- dure isotope characterization at the MC-ICP-MS Lab of Centre for Isotopic Research on Cultural and Environmetal heritage (CIRCE). A series of treated and untreated refer- ence material (NIST SRM 986) samples were measured together with some terrestrial (USGS) samples already measured in other studies [3] in order to evaluate procedure and machine characteristics. FInally samples from the Chonditres of Brenham e and Mineo.

Speaker: Fabio Marzaioli (INFN Napoli)

Abstract 195-Marzaioli.pdf

99 Multi-d core collapse nucleosynthesis: the effect of different reaction rate libraries

The explosion of massive stars as core-collapse supernovae represents one of the outstanding problems in modern astrophysics. Core-collapse supernovae figure prominently in the chemical evolution of galaxies as the dominant producers of elements between oxygen and the iron group, and they play an important role in the production of elements heavier than Fe. They represent a key ingredient in understanding the history of chemical enrichment of the Universe. We present in this work a detailed analysis of nucleosynthesis calculations of a 15 M neutrino-driven supernova explosions in 3D (explosions, approximative neutrino treatment, progenitors are presented by Wongwathanarat et al. 2017). Nucleosynthesis calculations are performed in a post-process using tracer particles method (TONiC code, Travaglio et al. 2011). The nucleosynthesis network used is based on 1500 isotopes, and for the first time about 500.000 tracer particles cover the star up to the explosive C-burning shell. A detailed analysis on consequences using different nuclear reaction networks (theoretical as well as experimental ones). The nuclear processes included are electron captures, neutron captures, alpha captures and photodisintegrations. The same comparison has been performed using 3D as well as 1D models (where also the 1D model includes neutrino-driven explosion) and will be discussed in this poster. Expertises in stellar/hydrodynamic treatment of the explosion, explosive nucleosynthesis, nuclear rate from the theoretical as well as from the experimental point of view are included in this group of authors making this work possible and very much detailed.

Speaker: Claudia Travaglio (INAF - OATO)

Abstract 131_Travaglio.pdf

100 Neutron capture cross sections on Zn and Ge isotopes for the weak s process

Many of the atoms with atomic mass numbers 60 A 90 have their origins in the weak s process occurring in massive stars. The abundances produced in the weak s process are sensitive to individual neutron capture cross sections that can have a broad impact on nucleosynthesis. There is limited neutron capture cross section data especially at energies relevant for shell carbon burning near kT approx 90 keV that extends into the unresolved resonance region. Cross sections are difficult to predict theoretically, and recent calorimetric measurements have shown that contributions from scattered neutrons and small target impurities could impact the reliability of earlier measurements in some cases (e.g. see. We will present recent measurements of neutron capture cross sections on stable isotopes of Zn and Ge using neutron time-of-flight with highly enriched samples and the Detector for Advanced Neutron Capture Experiments (DANCE) at the Manuel Lujan Neutron Science Center at LANSCE. DANCE is a 4pi BaF_2 calorimeter that allows neutron capture on different isotopes to be distinguished by the neutron-capture Q-value. Particular care was taken in these measurements to characterize systematic uncertainties and contributions from scattered neutrons and isotopic impurities that can be significant. The experiments, analysis, preliminary results, and implications for nucleosynthesis in the weak s process will be presented.

Speaker: Jeffery Blackmon (Louisiana State University)

Abstract blackmon-NIC2018.pdf

101 Neutron star parameter estimation using large grids of multizone X-ray burst models

In recent years, multizone simulations have been used to successfully model various observed features of thermonuclear X-ray bursts on neutron stars (NS), including recurrence times, burst energies, and lightcurve profiles. Although previous multizone studies have explored the dependence of burst properties on system parameters, and compared individual models with observations, no large-scale parameter estimation has yet been performed. This is a crucial step if burst simulations are to be used for constraining neutron star system parameters. We present a framework for creating large grids of burst models with the KEPLER code, and then iterating over the results with Markov chain Monte Carlo (MCMC) methods. Although multizone models are generally too expensive to calculate "in situ", we can overcome this by pre-computing a grid of simulations, and interpolating the outputs. We present preliminary results using this method to model the famous "clocked burster" GS 1826-24, to obtain constraints on system parameters such as accretion rate, fuel composition, crustal heating, and the NS mass and radius.

Speaker: Zac Johnston (Monash University)

Abstract 49_JohnstonZac.pdf

102 New improved indirect measurement of the 19F(p,alpha)16O reaction[5mm]

The 19Fp,alpha_0 16O is the main fluorine destruction channel at the bottom of the convective envelope in Asymptotic Giant Branch (AGB). Because of the Coulomb barrier, direct measurements cannot access to the energy region of astrophysical interest (below 500 keV). We report on the indirect measurement of the alpha_0 channel using the Trojan Horse Method (THM). Before THM measurement, only extrapolations were available below about 500 keV, showing a non resonant behaviour, sharply contradicting the trend of the astrophysical factor at higher energies \cite{nacre}. A previous indirect experiment using the THM has observed the presence of three resonances in the energy regions below E_cm approx 450 keV, energies corresponding to typical AGB temperatures, thus implying a significant increase in the reaction rate with respect to the NACRE extrapolation \cite{nacre}, assuming an almost constant S-factor. Anyway, statistics turned out to be scarce to perform an accurate separation between resonances, preventing one to draw quantitative conclusions on their total widths and spin parities. A new experiment has been performed to verify the measured TH astrophysical factor and to perform more accurate spectroscopy of the involved resonances, in the light of the new direct measurements confirming previous results and providing better identification of the involved states. The Tandem accelerator of the Laboratori Nazionali di Legnaro provided a 55 MeV 19F beam with a spot size on target of 1 mm and intensities around 1-3 nA. Thin self-supported deuterated polyethylene target (CD_2) of about 100 mug/cm2 were used to minimize energy and angular straggling, placed at 90^\circ with respect to the beam direction. We used the modified R-matrix approach to investigate the energy region E_{cm} < 1 MeV, so as to span both the range of astrophysical interest and the 0.6 < E_{cm}< 0.8 MeV interval needed for normalization. The new experiment has confirmed and improved the measured TH S-factor and it has allowed to obtain more accurate resonance data at astrophysical energies. From the modified R-matrix calculation the reaction rate has been calculated. We compare the present 19F(p,alpha_0)16O reaction rate with the one reported in. At the astrophysically relevant temperatures T_9= 0.04-0.2, the rate from the present work agrees, within errors, with the one obtained by \cite{Laco2} and there is only a small difference (sim10%) between the two adopted values. A larger discrepancy (sim 30%) is found at temperature T$_9 sim 0.4 due to the interference of 0.113 and 0.251 MeV resonances.

Speaker: Iolanda Indelicato (INFN-LNS)

Abstract 70_IndelicatoIolanda.pdf

103 New resonance strength measurements for the 30Si(p,g)31P reaction

The observational evidence for multiple stellar populations within globular clusters continues to confound the astronomical community. These populations are usually interpreted as distinct generations, with the currently observed second-generation stars having formed in part from the ejecta of massive, first-generation ``polluter" stars, giving rise to anomalous abundance patterns. The identity of the polluter stars as well as their mechanism of enrichment are not yet understood. A recent study of the Mg-K abundance anomaly measured in the cluster NGC 2419 used reaction network Monte Carlo simulations to identify the stellar temperature and density conditions that may have given rise to this polluter material. In a follow up sensitivity study, we found several nuclear reactions that were highly influential in determining these conditions and suggested a series of experiments to reduce their rate uncertainties. We now report results for the first resonance strength experiments in this series, direct measurements of the E$_p=$ 432 keV and E$_p=$ 499 keV resonances in the $^{30}$Si(p,$\gamma$)$^{31}$P reaction. We present a new recommended reaction rate and also explore its effect on the problem of polluter material parentage in NGC 2419.

Speaker: John Dermigny (University of North Carolina)

Abstract 140_Dermigny.pdf

104 Nuclear Energy Generation in the r-Process

The recent observation of an optical afterglow (“kilo- or macronova”) in the aftermath of the gravitational wave event GW170817 has confirmed that neutron star mergers are an operating site of the r-process. In such an event, energy that is released in nuclear reactions during the r-process can thermalize with the ejecta and act as a heating source. This feedback of energy influences the dynamics of the ejecta and the ejecta mass and thus needs to be accounted for in hydrodynamical simulations of neutron star mergers. Furthermore, the late-time decays of radioactive nuclei that have been produced by the r-process power the kilonova light curve. The direct connection between nuclear decays and the evolution of the observed light curve allows for new insights into the mechanism of the r-process. We will present the dependency of nuclear energy generation in the r-process on electron fraction, entropy, dynamical timescale, and for different theoretical mass models. Moreover, we give a new formula for heating in hydrodynamical models. We are also exploring the behaviour of late-time decays to stability relevant for the kilonova light curve and discuss interesting cases that result in a unique heating rate.

Speaker: Marius Eichler (Technische Universitaat Darmstadt)

Abstract 161-Eichler.pdf

105 Nuclear Physics Constraints on Possible Resonances in Carbon Fusion Reaction and Its Impact on Type Ia Supernovae

The 12C+12C reaction is one of the most important reactions in astrophysics. The reaction ignites type Ia supernovae (SNe Ia), which are used as a standard candle in cosmology and are the major factory of the iron group elements in galaxies. In addition, it is a possible fuel of X-ray superbursts, whose ignition mechanism is still unclear. In spite of its importance, the cross sections of this reaction in astrophysical low energies have not been measured. Especially, unknown resonances in the low energy region can enhance the reaction rate and affect astrophysics. We constrain an upper limit of such resonances with the Wigner limit, and find that the astrophysical reaction rate can be enhanced by sim 10^3 times compared with a standard rate if they exist. We study the impact of the enhanced rate on the evolution of white dwarf-white dwarf (WD-WD) binary mergers, which is a hypothetical progenitor of SNe Ia. It is shown that ignition temperature determined by competition between cooling by neutrino emission and heating by carbon burning decreases due to the resonances. Therefore, the number of SNe Ia that comes from WD-WD mergers decreases, while the number of neutron stars increases.

Speaker: Kanji Mori (National Astronomical Observatory of Japan)

Abstract 11_MoriKanji.pdf

106 Nuclear physics of 26Al production

The ground state of the unstable 26Al nucleus (26Alg) with T_1/2 = 0.717 Myr was the first radioisotope detected in the galaxy, via the characteristic 1.809 MeV gamma-emission of 26Mg. The observation is direct proof of ongoing stellar nucleosynthesis in our Galaxy and indicates that there are approximately 2-3 M_odot of 26Alg. It is therefore fundamental to understand the production of 26Alg and the effect of the nuclear physics uncertainty. 26Al has a isomeric state (26Alm) which is prohibited to decay into 26Alg due to the large spin difference. However, an equilibration between 26Alm and 26Alg could proceed via intermediate states and influence the abundance of 26Alg. Hence, the isomer could have an important influence on the production of 26Alg. To clarify the production mechanism of 26Alg in the winds of massive stars, we present our investigation of the sensitivity of the yields to variation of nuclear reaction rates involving 26Alg and 26Alm.

Speaker: E. T. Li (Shenzhen University)

Abstract ET_Li.pdf

107 Nucleosynthesis of 60Fe and constraints on the nuclear level density and γ-ray strength function.

60Fe is created by neutron capture in massive stars prior to core collapse supernova. This isotope is one of only a handful whose gamma-rays from β-decay indicate ongoing nucleosynthesis in the Galaxy [1]. For this reason the reactions involved for the creation and destruction of 60Fe in this environment must be well understood. Due to the short half-life of 59Fe it is challenging to perform a direct capture reaction experiment to determine the cross section of 59Fe(n,γ)60Fe. Instead we used the β-decay of 60Mn to populate states at all energies in the 60Fe nucleus. The resulting γ-rays were collected using a 4π total-absorption spectrometer, SuN (Summing NaI(Tl) detector) [2], at the NSCL. With this data the β-Oslo method [3] can be applied to extract the nuclear level density and gamma-strength function needed for statistical models to calculate the reaction rate using experimentally constrained nuclear structure parameters. Preliminary results from the ongoing analysis will be presented.

Speaker: Debra Richman (NSCL, Michigan State University)

Abstract 154-Richman.pdf

108 Nucleosynthesis of trans-iron elements in magneto-rotational core-collapse supernovae

Magnetically driven supernovae of massive stars are expected as viable sites of heavy-nuclei including r-process nuclei as well as the central engine of gamma-ray bursts and magnetar formation supernovae. In this talk, I show recent results of r-process nucleosynthesis based on magneto-hydrodynamical models taking into account the enhancement processes of magnetic fields due to magneto-rotational instability around the proto-neutron star. We found that the weak r-process occurs in models with the weaker magnetic-driven jet influenced by neutrino-heating, while the cases with strong magnetic-jets produce heavy nuclei. I also discuss the role of magnetically driven supernovae in the chemical enrichment history in galaxies as an alternative source of heavy elements.

Speaker: Nobuya Nishimura (YITP, Kyoto University)

Abstract 198-Nishinura.pdf

109 On Barium stars and the s process in AGB stars

Barium stars belong to a binary system where the companion star has evolved through the AGB phase and transferred elements heavier than Fe produced by the slow neutron-capture process onto the secondary star, which is now observed. A new large set of homogeneous high resolution spectra of Ba stars makes it now possible to meaningfully compare the observational data with different AGB models and with other observations. The Ba star data shows an incontestable increase of the hs-type/ls-type element ratio (for example, Ce/Y) with decreasing the metallicity, but when comparing with post-AGB observations there is a clear difference between the two datasets. The trend in the Ba star observations is predicted by non-rotating AGB models where 13C is the main neutron source. This poses the question if the post-AGB stars show the signature of the i process or somehow represent a different AGB population. Observations of the cores of red giant stars and of white dwarfs (the ancestors and the progeny of AGB stars, respectively) inferred via asteroseismology from Kepler observations show low core rotational velocities, which is in agreement with the results from the Ba star data and may derive from coupling between the core and the envelope.

Speaker: Ms Borbála Cseh (Konkoly Observatory, MTA CSFK)

Abstract abstractNIC2018CsehB.pdf

110 On the activation method for stellar cross-sections measurements: flat sample correction in measurements relatives to gold.

Maxwellian-averaged cross-sections (MACS) are needed as an input for the models of stellar s- and r-processes nucleosynthesis. In many cases, MACS can be obtained from activation measurements, irradiating a flat sample with the neutron field generated by the 7Li(p,n)7Be reaction at 1912 keV proton energy (a quasi-maxwellian neutron spectrum or QMNS). In most measurements, the sample is placed between gold foils, and the gold cross section is used as a reference. Data analysis to obtain the MACS includes a correction for the difference between a quasi-maxwellian neutron spectrum (QMNS) vs. a true maxwellian one. This spectrum correction is depending on the sample cross-section behavior. However, an additional correction taking into account the effect of the incidence angle of the neutrons into a flat sample and the subsequent variation in the effective mass thickness experienced by the neutrons, has not been historically taken into consideration in this measurements relative to gold. This correction is also depending on the energy-angle distribution of the neutron flux and on the sample cross-section. So, this flat sample correction in general will have different values for gold and for the measured sample, and therefore it can't be cancelled in relative measurements. We have calculated that this missing correction could affect these activation relative measurements results in some cases up to a 2-3%. We propose an analytic expression for the calculation of this flat simple correction, and we suggest a revision of the existing activation measurements results. Recently it has been showed that is possible to generate a closer maxwellian neutron spectrum at kT=30 keV if we shape the energy profile of the incident proton beam. With this method (MNS), the spectrum correction is highly reduced. However, in this case the mentioned flat sample correction is increased, due to a higher aperture of the neutron flux cone (more than 90 degrees). We propose a further improvement in the activation technique, consisting on a modified experimental geometry, in which the samples are placed slightly further from the neutron source, covering a lower solid angle. In this way, the flat sample corrections are highly reduced, while the spectrum correction is maintained low.

Speaker: Pablo Jimenez Bonilla (University of Seville)

Abstract 201-Bonilla.pdf

111 On the measurements of the beam characteristics of the JUNA 400 kV accelerator and 14N(p,g)15O reaction

Jinping Underground laboratory for Nuclear Astrophysics (JUNA) is one of the major research programs in China JinPing underground Laboratory (CJPL). To study key nuclear reactions in astrophysics, a new 400 kV accelerator, with high stability and high intensity, has already been constructed by CIAE and IMP in 2017 and will be installed into CJPL in 2019. Currently, the beam characteristics of the JUNA 400 kV accelerator, like absolute energy, energy spread and long-term energy stability, are measured by the resonance reactions of 25Mg(p,g)26Al, 26Mg(p,g)27Al and 27Al(p,g)28Si, and non-resonance 12C(p, g)13N. The 14N(p,g)15O reaction will also be studied near Gamow energy in JUNA project. The results of beam characteristics and the progress of 14N(p,g)15O reaction will be presented.

Speaker: Shuo Wang (Shandong University)

Abstract 7_WangShuo.pdf

112 On the Origin of the Early Solar System Radioactivities. Problems with the AGB and Massive Star Scenarios

Recent improvements in stellar models for intermediate-mass and massive stars are recalled, together with their expectations for the production of radioactive nuclei with lifetime tau 25 Myr, in order to re-examine the origins of now extinct radioactivities, found to be alive in the Early Solar System. While the inheritance from Galactic evolution broadly explains the concentrations of most of them +06, 26Al, 56Fe, 41Ca and 135Cs require one or more nucleosynthesis events occured close in time and space to the solar formation. We outline the difficulties to account for the required nuclei by Asymptotic Giant Branch stars. Recent physical models predict the ubiquitous formation of a 13C reservoir as a source for efficient neutron captures. As a consequence, even in presence of 26Al production from Deep Mixing or Hot Bottom Burning, the foreseen ratio 26Al 107Pd remains incompatible with the measured data, due to a large excess in 107Pd. This is shown with reference to two different approaches to Deep Mixing. Instead, recent revisions invoking specific supernovae of relatively low mass and/or scenarios for the sequential contamination of the pre-solar molecular cloud would most probably induce a huge excess on 60Fe and unacceptaly high excesses on stable isotopes. The limited parameter space remaining to be explored for solving this puzzle is discussed.

Speaker: Diego Vescovi (GSSI & INFN Perugia)

Abstract vescovi_abstract.pdf

113 Physics with OSCAR at the Oslo Cyclotron Laboratory

For more than 20 years, researchers working at the Oslo Cyclotron Laboratory (OCL) have been dedicated, among other things, to exploring the statistical properties of nuclei in the quasi-continuum. Oslo-method experiments simultaneously provide experimental values of the nuclear level density and the γ-strength function of nuclei [1], both necessary ingredients for (n,γ) cross section calculations, with implications in nuclear technology and astrophysics. Recently, the CACTUS array of NaI detectors at the OCL has been replaced by OSCAR, a new array of 30 cylindrical, large volume (3.5 ′′ × 8 ′′) LaBr3:Ce detectors. The higher efficiency, and the better energy and time resolutions of OSCAR, open up new experimental possibilities. Some details of the OSCAR array and the physics experiments at the OCL will be presented in the contribution. [1] A. Schiller et al., Nucl. Instrum. Methods Phys. Res. A 447(2000)498.

Speaker: Frank Leonel Bello Garrote (University of Oslo)

Abstract 179-Ingeberg.pdf

114 Preparing micrometeorites for cosmogenic 26Al and 10Be measurement - identification without significant mass loss

Each year, roughly 30,000 tons of extraterrestrial solid material, liberated from larger parent bodies within our Solar System, is captured by the Earth [1]. A significant fraction of this material are submillimetre-sized spherical to teardrop-shaped particles, termed micrometeorites. They represent signatures of asteroidal collisions and cometary sublimation [2], hence, the determination of their origin gives valuable information on recent cosmic events and processes. Their cosmic ray exposure age can be derived by measuring cosmic ray-induced spallation products such as the long-lived radionuclides 26Al and 10Be that accumulate within the particles during their journey through space (e.g. [3]). The low concentrations of 26Al and 10Be within micrometeorites are close to the detection limits of current accelerator mass spectrometry (AMS), hence, any loss of material for their identification and classification as micrometeorites needs to be minimized. Surface composition analyses with EDX-measurements can lead to misidentifications, since these particles have melted during entry, and do not represent the total composition. For identifying micrometeorites with high confidence, it is necessary to analyze the interior of the particle [4], commonly through epoxy embedded cross-section EDX-analysis, which, however, leads to substantial material loss [5]. We present a new methodology on how to identify micrometeorites without a substantial material loss, nor impediments such as coating and epoxy embedding. Using a focused ion beam (FIB) on the non-coated particle, we are able to cut off a thin slice of the surface. Subsequently, with field emission electron probe microanalysis (FE-EPMA), its inner composition (and textures) can be determined quantitatively at lower detection limits down to a few tens of ppm with wavelength dispersive X-Ray spectrometers. Here, we show first results on 50-150 um diameter micrometeorites collected from Antarctic moraine sediments originating from the Larkman Nunataks aeolian traps [6]. References [1] S.G. Love and D.E. Brownlee, Science 262 (1993) 550. [2] G.M. Raisbeck et al., 49th Ann. Meet. Meteorit. Soc. 600 (1986) 136. [3] K. Nishiizumi et al., Meteorit. Planet. Sci. 30 (1995) 728. [4] J. Larsen and M.J. Genge, 79th Ann. Meet. Meteorit. Soc. 1921 (2016) 6341. [5] M.D. Suttle and M.J. Genge, Earth. Planet. Sci. Lett. 476 (2017) 132. [6] M.D. Suttle, et al., 78th Ann. Meet. Meteorit. Soc., 1856 (2015) 5063.

Speaker: Jenny Feige (Technical University Berlin)

Abstract 77_FeigeJenny.pdf

115 Presolar SiC grains of Type AB with isotopically light nitrogen: Contributions from supernovae?

Primitive solar system materials contain small concentrations of presolar grains that formed in the winds of evolved stars and in the ejecta of stellar explosions [1]. Presolar SiC is the best studied presolar mineral. Among them are so-called Type AB grains which have low 12C/13C ratios of <= 10. This population of presolar SiC grains appears to originate from multiple types of stellar sources, namely, supernovae (SNe) for grains with isotopically heavy N (14N/15N < 440) [2], and born-again AGB stars [3] and in particular J-type carbon stars for grains with isotopically light N (14N/15N >= 440) [4]. Here, we report on high resolution (< 100 nm) measurements of C-, N-, Mg-Al-, Si-, and S-isotopic compositions of 10 SiC AB grains from Murchison separate KJD (median size 0.81 micrometer) [5] conducted with the NanoSIMS ion probe at MPI for Chemistry with Cs and Hyperion O ion sources. Except for one grain with the highest 12C/13C ratio we find good correlations between 12C/13C, 14N/15N, and 26Al/27Al. There is an almost perfect 1:1 correlation between Al and N concentrations, suggestive of AlN and low levels of contamination. Magnesium is essentially monoisotopic 26Mg from 26Al decay (half life: 0.72 Myr). Sulfur isotope anomalies are generally small and Si-isotopic compositions plot along the SiC mainstream line. Four of our AB grains have light N with 14N/15N up to 1000. The correlations between C-, N-, and Al-isotopic ratios are well explained by the 25 Msun SN model 25T-H of [6] when matter from the O/nova zone, which experienced explosive H burning, and above (6.847-13.3 Msun) is mixed with matter that experienced only partial H burning, taken from the outer layers in the 12 Msun model of [7], as suggested by [2], and if the 12C/13C ratio in the 25T-H model is decreased by a factor of 3. The comparison of our data with model 25T-H suggests that SNe might have contributed not only AB grains with heavy N but also some of those with light N. [1] E. Zinner, in Treatise on Geochemistry, ed. A. M. Davis, Vol. 1(2014)181. [2] N. Liu et al., ApJL 842(2017)L1 [3] S. Amari et al., ApJ 559(2001)463 [4] N. Liu et al., ApJL 844(2017)L12 [5] S. Amari et al., GCA 58(1994)459 [6] M. Pignatari et al., ApJL 808(2015)L43 [7] S. Woosley & A. Heger, PhR 442(2007)269

Speaker: Peter Hoppe (Max Planck Institute for Chemistry)

Abstract Hoppe_NIC2018.pdf

116 Program and progress of the Felsenkeller shallow-underground accelerator for nuclear astrophysics

Low-background experiments with stable ion beams are an important tool for putting the model of stellar hydrogen, helium, and carbon burning on a solid experimental foundation. The pioneering work in this regard has been done by the LUNA collaboration at Gran Sasso, using a 0.4 MV accelerator. The present contribution reviews the status of the project for a higher-energy underground accelerator in Felsenkeller, Dresden/Germany. Measurements of the gamma-ray background have shown satisfactory background there, when the 45 m rock overburden is combined with an active veto against remaining muons. Two tunnels of the Felsenkeller underground site have recently been refurbished for the installation of a 5 MV high-current Pelletron ion accelerator. Civil construction has completed in March 2018. The accelerator and analyzing magnets are already in the tunnel, and the setting up of the beam lines is ongoing. The accelerator will provide up to 50 uA beams of 1H+, 4He+, and 12C+ ions, enabling research on astrophysically relevant nuclear reactions with unprecedented sensitivity. As part of the in-house research by HZDR and TU Dresden, two nuclear reactions shall be studied at Felsenkeller: The 12C(alpha,gamma)16O reaction which controls the carbon-to-oxygen ratio at the end of stellar helium burning, and the 3He(alpha,gamma)7Be reaction which affect the fluxes of solar 7Be and 8B neutrinos. In addition, the accelerator will be open as a facility to outside users from any field of science, free of charge and with access granted based on the recommendations of an independent scientific advisory board.

Speaker: Daniel Bemmerer (Helmholtz-Zentrum Dresden-Rossendorf)

Abstract 71_BemmererDaniel.pdf

117 Pulse Shape Discrimination for high pressure 3He counters

The success of low counting rate experiments strongly depends on the accurate knowledge and reduction of the backgrounds present during the measurement campaigns. For this reason, dark matter search and low energy nuclear astrophysics experiments are performed in underground laboratories, shielded from the cosmic rays. Two important examples of low counting rate experiments for nuclear astrophysics are the measurement of 13C(alpha,n) and 22Ne(alpha,n) cross-sections at low energies, which are considered to be the main neutron sources for the astrophysical s-process. These experiments require the use of high intrinsic efficiency detectors, such as the high pressure 3He counters, sensitive to thermal neutrons through the 3He(n,p) reactions. The intrinsic alpha-activity contained in the walls of these counters becomes a major source of background in low count rate scenarios. Nevertheless, the neutron signal events can be masked by the internal alpha background present in the aluminium housing, complicating the uncertainty objectives for the experimental cross-section measurements. To reduce this intrinsic background, over the years, many efforts were made in the pulse shape discrimination between the neutron and alpha event signature. Two recent examples are the use of current sensitive preamplifiers, taking advantage of the double peak structure formed by the triton and proton articles and low pressure 3He counters, for which the rise-time differences between alpha and 3He(n,p) events permit pulse shape discrimination. However, most experiments are performed with charge sensitive preamplifiers in the electronic chain, thus losing the double peak structure of 3He(n,p) reactions, and the usage of higher-pressure (and thus higher-efficiency) counters limits the usefulness of discrimination by rise time neither benefited by the rise-time differences signals of the low pressure 3He detectors. We will present an improved pulse shape discrimination methodology developed for high pressure 3He counters read out through charge sensitive preamplifiers electronics using standard digitizing methods, and a Monte Carlo simulation of the detector response to the different particle interactions.

Speaker: Javier Balibrea Correa (INFN Napoli)

Abstract 76_BalibreaCorreraJavier.pdf

118 PUSHing Core-Collapse Supernovae to Explosions in Spherical Symmetry: Explodability and Global Properties

Core-collapse supernovae (CCSNe) are energetic explosions occurring at the end of the evolution of massive stars that provide the conditions for the synthesis of elements beyond iron and contribute to the galactic chemical evolution. Decades of research have not fully uncovered the detailed mechanism behind these complex explosions. Multi-dimensional simulations are crucial to investigate the mechanism, but computationally too demanding to investigate global properties of large samples of progenitor models. For this, spherically symmetric simulations are still the best-suited tool at the present time. The PUSH method [1] represents a well-suited parametrized framework to investigate the neutrino-driven mechanism in one-dimensional simulations to efficiently study important aspects of CCSNe like the effects of the shock passage through the star, the progenitor-remnant connection [2] and explosive nucleosynthesis [3]. With a calibration of the method to SN1987A and other observed CCSNe we explore the explodability and global properties of CCSN simulations for a large mass range of available solar metallicity progenitors. We find, among other properties, the explosion energies, ejected nickel masses, and remnant masses for the investigated progenitor samples and predict the resulting neutron star and black hole birth mass distributions. [1] A. Perego, M. Hempel, C. Fröhlich, K. Ebinger et al., ApJ 806, 275 (2015). [2] K. Ebinger, S. Curtis, C. Fröhlich et al., (submitted for publication). [3] S. Curtis, K. Ebinger, C. Fröhlich et al., (submitted for publication).

Speaker: Kevin Ebinger (GSI)

Abstract 150-Ebinger.pdf

119 PUSHing Core-Collapse Supernovae to Explosions in Spherical Symmetry: Nucleosynthesis Yields

Core-collapse supernovae (CCSNe) are one of the most important sites of element synthesis in the universe. Not only do they drive the chemical evolution of galaxies, the nucleosynthesis yields of CCSNe are also imprinted on some of the oldest stars. However, our ability to predict nucleosynthesis yields is limited by the still unresolved question of the CCSN explosion mechanism. The PUSH method is a parametrized spherically symmetric explosion method that can reproduce many features of CCSNe for a wide range of pre-explosion models [1, 2]. This method also follows the evolution of the protoneutron star and the electron fraction of the ejecta - features that are crucial for nucleosynthesis calculations. Here, we will discuss the nucleosynthesis yields of all successful explosion models from Ebinger et al. (2017). This includes two sets of pre-explosion models at solar metallicity, with combined masses between 10.8 and 120 Msun. We compare the predicted 56Ni ejecta to observationally derived values for normal CCSNe. We highlight broad trends that appear as a function of pre-explosion model properties and explosion properties. We also predict iron-group yields that are in agreement with derived abundances for metal-poor star HD 84937. We provide detailed and complete isotopic yields for all our models [3, 4]. These yields will be extremely useful for modeling galactic chemical evolution to gain further insight into the nuclear history of our universe. References [1] A. Perego, M. Hempel, C. Fröhlich et al., ApJ, 806, 275, (2015). [2] K. Ebinger, S. Curtis, C. Fröhlich et al., (Submitted to ApJ, under revision). [3] S. Curtis, K. Ebinger, C. Fröhlich et al., (Submitted to ApJ, under revision). [4] http://astro.physics.ncsu.edu/~cfrohli/

Speaker: Sanjana Curtis (North Carolina State University)

Abstract sanjana.pdf

120 R-process Nucleosynthesis in Core-collapse Supernova Explosions and Binary Neutron Star Mergers

R-process nucleosynthesisin core-collapse supernova explosions (CCSNe) and binary neutron star mergers (NSMs), both of which are promissing candidates for the r-process sites, are studied using new beta-decay half-lives for the waiting-point nuclei obtained by shell-model calculations. We here investigate how the change of beta-decay half-lives affects the r-process nucleoasynthesis. Beta decay rates for exotic nuclei with neutron magic number of N=126 are evaluated up to Z=78 by including the contributions from both the Gamow-Teller and first-forbidden transitions. The half-lives obtained prove to be short compared to a standard finite-range-droplet model (FRDM), in particular near $^{208}$Pb region due to the effects of the first-forbidden transitions. The element abundances for the r-process in neutrino-driven wind CCSNe, magnethydrodynamic jet CCSNe and binary NSMs are obtained up to the third peak as well as beyond the peak region up to thorium and uranium. The position of the third peak is found to be shifted toward a higher mass region in both CCSNe and NSMs. We find that thorium and uranium elements are produced more with the shorter shell-model half-lives and their abundances come closer to the observed values in CCSNe. In case of binary NSMs, thorium and uranium are produced as much as consistent with the observed values independent of the half-lives. This suggests that NSMs are promissing robust r-process sites for producing very heavy elements such as thorium and uranium.

Speaker: Toshio Suzuki (Nihon University)

Abstract 39_SuzukiToshio.pdf

121 Radiative alpha capture on 7-Be with DRAGON at energies relevant to the νp-process

The origin of about 35 neutron-deficient stable isotopes with mass number A 74, known as the p-nuclei, has been a long-standing puzzle in nuclear astrophysics. The νp-process is a candidate for the production of the light p-nuclei, but it presents high sensitivity to both supernova dynamics and nuclear physics [1,2]. It has been recently shown that the breakout from pp-chains through the 7-Be(α,γ)11-C reaction, which occurs prior to νp-process, can significantly influence the reaction flow, and subsequently the production of p-nuclei in the 90 A 110 region [2]. Nevertheless, this reaction has not been studied well yet in the relevant temperature range - T= 1.5-3 GK. To that end, the first direct study of important resonances of the 7-Be(α,γ)11-C reaction with unknown strengths using DRAGON [3] was recently performed at TRIUMF. The reaction was studied in inverse kinematics using a radioactive 7-Be (t1/2= 53.24 d) beam provided by ISAC-I and two resonances above the 11-C α-separation energy - Qα = 7543.62 keV - were measured. The experimental details, in particular how the recoil transmission and BGO efficiencies were accounted for considering the large cone angle for this reaction, will be presented and discussed alongside some preliminary results. References [1] C. Frohlich et al., Phys. Rev. Lett. 96, 142502 (2006). [2] S. Wanajo, H.-T. Janka and S. Kubono, Astrophys. J. 729, 46 (2011). [3] D.A. Hutcheon et al., Nucl. Instr. Meth. Phys. Res. A 498, 190 (2003).

Speaker: Athanasios Psaltis (McMaster University)

Abstract 19_PsaltisAthanasios.pdf

122 Reverse engineering the properties of neutron-rich lanthanides using the r-process rare-earth abundance peak

The recent observations of the GW170817 electromagnetic counterpart suggest lanthanides were produced in this neutron star merger event. Lanthanide production in heavy element nucleosynthesis is subject to large uncertainties from nuclear physics and astrophysics unknowns. Specifically, the rare-earth abundance peak, a feature of enhanced lanthanide production at A~164 seen in the solar r-process residuals, is not robustly produced in r-process calculations when astrophysical and nuclear physics inputs are varied. The proposed dynamical mechanism of peak formation requires the r-process path to encounter a nuclear deformation maximum or sub-shell closure in the rare-earth region which may be within reach of nuclear physics experiments performed at, for example, the CPT at CARIBU and the upcoming FRIB. To maximize what can be learned regarding nucleosynthesis from such precision measurements, we employ Markov Chain Monte Carlo studies to "reverse engineer" the nuclear masses capable of producing a peak compatible with the observed solar r-process abundances given different sets of astrophysical conditions. Here I will present the latest results for the masses found to produce the rare-earth peak in a low entropy accretion disk wind scenario and compare directly with recent mass measurements from the CPT at CARIBU. Such collaborative efforts between theory and experiment could soon be in a position to make definitive statements regarding the mechanism of rare-earth peak formation and thus the astrophysical site of the r process.

Speaker: Nicole Vassh (University of Notre Dame)

Abstract 117_Vassh.pdf

123 Rotation and slow neutron capture nucleosynthesis

The slow neutron capture process (s-process) is responsible for about half of all ele- ments heavier than iron in the universe, and is therefore important for galactic chemical evolution. Its main production site is the Asymptotic Giant Branch (AGB) phase, a stellar evolution phase in stars with an initial mass between about 0.8 and 8 M⊙. As stars rotate, it is important to calculate stellar evolution models of these stars in- cluding rotation. Currently, only one complete set of rotating AGB models exists (see [1], and http://fruity.oa-teramo.inaf.it/). There is only one, because the implementation of rotation and rotation-induced mixing in stars is uncertain and does not reproduce all observables. Specifically, recent observables obtained by asteroseismology show a process of angular momentum transport is missing in stellar evolution theory. We will show that the uncertainties in the implementation of rotation lead to unphysical features in our AGB models, that strongly influence the s-process nucleosynthesis. We will present new AGB models including rotation that also include an additional, artifi- cial viscosity, which reduces these unphysical features. Adding this artificial viscosity is motivated by current efforts to constrain the missing process of transport of angular momentum (see [2] and more recently [3]). We will show the impact of this artificial viscosity on the AGB phase and its nucleosynthesis.

Speaker: Jacqueline den Hartogh (Konkoly Observatory)

Abstract DenHartogh_abstractNIC2018.pdf

124 Sensitivity studies on the excited states of the beta decays in one zone model of X-ray bursts

In this paper, we investigate the sensitivities of positron decays on a one-zone model of type-I X-ray bursts. Most existing studies have multiplied or divided entire beta decay rates (electron captures and beta decay rates) by 10. Instead of using the standard Fuller and Fowler (FFNU) rates, we used the most recently developed weak library rates, which include rates from Langanke et al.'s table (the LMP table), Langanke et al.'s table (the LMSH table), and Oda et al.'s table (all shell model rates). We then compared these table rates with the old FFNU rates to study differences within the final abundances. Both positron decays and electron capture rates were included in the tables. We also used pn-QRPA rates to study the differences within the final abundances. Many of the positron rates from the nuclei's ground states and initial excited energy states along the rapid proton capture (rp) process have been measured in existing studies. However, because temperature affects the rates of excited states, these studies should have also acknowledged the half-lives of the nuclei's excited states. Thus, instead of multiplying or dividing entire rates by 10, we studied how the half-lives of sensitive nuclei in excited states affected the abundances by dividing the half-lives of the ground states by 10, which allowed us to set the half-lives of the excited states. Interestingly, we found that the peak of the final abundance shifted when we modified the rates from the excited states of the 105Sn positron decay rates. Furthermore, the abundance of 80Zr also changed due to usage of pn-QRPA rates instead of weak library rates (the shell model rates).

Speaker: Rita Lau (Technological and Higher Education Institute of Hong Kong)

Abstract 12_LauRita.pdf

125 Sensitivity studies on the excited states of the r-process nuclei in neutron star mergers

R-process is responsible for nearly half of the production of heavy elements in the universe. The nuclear input in the r-process is important in simulating formation of elements in the Universe. One of the properties is the excited states of nuclei in beta decays. There was study on the topic but using semi-gross theory and the single particle states were calcuated by theory as well as the situation was in spernovae. In our project, we use the single particle states that are measured from experiments and happen in neutron merging stars.It was found that couple of nuclei affect the the first peak of the abundance of the production of heavy elements as well as the rare-earth region.

Speaker: Rita Lau (Technolgical and Higher Education Institute of Hong Kong)

Abstract 141_Lau.pdf

126 Spectroscopic study on 39-Ca using the 40-Ca(d,t)39-Ca reaction for classical nova endpoint nucleosynthesis

In classical nova nucleosythesis repeated proton capture reactions and beta-decays produce proton-rich isotopes and the endpoint of this nucleosynthesis typically occurs in nuclei close to A ~ 40. There is currently a discrepancy between the observed and predicted isotopic abundances in this mass region. One particular reaction, 38-K(p,g)39-Ca is important in this regard. Nova simulations show that this reaction can alter the isotopic abundances of 38-Ar, 39-Ar, and 40-Ca significantly when the reaction rate is varied by its maximum uncertainty. Thus, it is important to constrain uncertainties of this reaction rate to accurately predict isotopic abundances. Although a recent direct measurement has reduced the reaction rate uncertainty, further work is needed to constrain this reaction rate. Specifically, additional measurements to precisely probe the low energy resonances within the Gamow window. To that end, I will present the preliminary results measuring these astrophysically important levels in 39-Ca using the reaction 40-Ca(d,t)39-Ca. The experiment was carried out at the Maier-Leibnitz-Laboratory (MLL) using the 14 MV MP-Tandem accelerator and Quadrupole 3-Dipole (Q3D) magnetic spectrograph.

Speaker: Johnson Liang (McMaster University)

Abstract 110_Liang.pdf

127 Stellar 36,38Ar(n,gamma)37,39Ar Reactions Studied at SARAF-LiLiT

As part of a program of neutron-capture measurements in the regime of the weak s-process, we studied for the first time the 36,38Ar(n,gamma) reactions in the stellar neutron energy regime and their contribution to production of light neutron-rich nuclides. The experiments were performed with the Liquid-Lithium Target (LiLiT) and the mA-proton beam at 1.92 MeV (2-3 kW) from the Soreq Applied Research Accelerator Facility (SARAF). The facility yields high-intensity quasi-Maxwellian (kT sim 30-50 keV) neutrons (3-5 times10^10 n/s). Gas samples were irradiated at the SARAF-LiLiT neutron source and the 37Ar36Ar and 39Ar/38Ar ratios in the activated gas samples were determined by accelerator mass spectrometry at the ATLAS facility (Argonne National Laboratory). The 37Ar activity was also measured by low-level counting at the University of Bern. The measured values of the Maxwellian Averaged Cross Sections (MACS) are significantly lower than theoretical and evaluated values published so far. Nucleosynthesis He-burning calculations using the 36,38Ar(n,gamma) experimental MACS show that the residual mass fraction of 36Ar increases by a factor of 10 while the mass fraction of neutron-rich nuclides in the region A=36-48 during the weak s-process is lowered by 10 to 50 %.

Speaker: Moshe Tessler (Hebrew University of Jerusalem)

Abstract abstractNIC2018_M_Tessler.pdf

128 Stellar evolutionary implications of updated light element (p,alpha) reaction rates

The complete understanding of the surface stellar abundances of light elements (lithium, beryllium, and boron) represents one of the most interesting open problems in astrophysics. These elements are gradually destroyed at different depths of stellar interior mainly by (p,alpha) burning reactions thus their surface abundances are strongly influenced by the nuclear burnings as well as by the extension of the convective envelope. Moreover their different fragility against (p,alpha) burning reactions allows one to investigate different depths of the stellar interior. The impact on surface abundances of the updated light element burning rates, as obtained with The Trojan Horse Method, is discussed.

Speaker: Scilla Degl'Innocenti (Pisa University & INFN)

Abstract Deglinnocenti.pdf

129 Stellar nucleosynthesis: experimental yields of the112Sn(gamma,n)111Sn and 112Sn(gamma,p)111m,g In reactions for p-nuclei production simulation

The nuclei of the overwhelming majority of the occurring in nature stable isotopes of medium and heavy chemical elements were synthesized in hot stars during the scenarios of rapid and slow neutron capture, that is (n,gamma)-reactions, and following beta-decays. However, in the formation of a so-called {p-nuclei} group including the 112Sn nuclide, simple photonuclear reactions of the (gamma,n), (gamma,p), and (gamma,alpha) type play a key role, and that is why this scenario was named the gamma-process. There is a need to know the rates of a large array of low energy nuclear reactions to simulate the current natural abundances of the p-nuclei. In the present work using the thin tantalum converter bremsstrahlung of the NSC KIPT (Kharkiv) electron linac for the target irradiations and high energy resolution gamma spectrometry for the induced radioactivity measurements we determined the integral yields of the 12Sn(gamma,p)111m,gIn(T_1/2=7.7m,J^{\pi}_{m}=1/2^{-}, Tg_{1/2}=2.8 d,J{pi}_{g}=9/2^+) and 112Sn(gamma,n)111Sn(T_1/2=35.3m) reactions in the relevant to astrophysical interest energy range between the threshold and 15 MeV. The results of the measurements are compared with the available data obtained by counting the neutrons and protons to be emitted, and with the calculations of the statistical theory of nuclear reactions implemented by the widely used for astrophysical calculations computer codes with different models of nuclear level density and radiation strength function. As an additional result, the branching coefficients of the strongest gamma-transitions between the 111In excited states populated at the 111Sn nucleus decay have been determined. They differ from the currently accepted values. References T. Rauscher, F.-K. Thielmann, ADNDT 80, 1 (2004). A.J. Koning, S. Hilaire and M.C. Duijvestijn, “TALYS-1.0”, Proceedings of the International Conference on Nuclear Data. for Science and Technology, April 22-27, 2007, Nice, France, editors O.Bersillon, F.Gunsing, E.Bauge, R.Jacqmin, and S.Leray, EDP Sciences, 2008, p. 211-214. http://www.nndc.bnl.gov/nudat2/.

Speaker: Anastasiia Chekhovska (V.N. Karazin Kharkiv National University)

Abstract 13_ChekhovskaAnastasiia.pdf

130 Stellar Yields of Rotating Pair Instability Supernovae and Comparison with Observations

After the onset of hydrodynamical collapse due to electron-positron pair creation, a very-massive star forming a massive CO core of ~65-120 Msun is considered to explode as a pair-instability supernova (PISN) [1]. Peculiar chemical yields as well as the high explosion energy characterize the PISN explosion [2,3]. Our final goal is to prove the existence of PISN and thus the high mass nature of the initial mass function in the early universe by conducting abundance profiling, in which properties of a hypothetical first star is constrained by metal-poor star abundances. For this purpose, we have investigated the PISN nucleosynthesis taking both rotating and non-rotating progenitors for the first time. In addition, we have conducted systematic comparison between theoretical yields and a large sample of metal-poor star abundances. We have found that the predicted low [Na/Mg] ~ −1.5 and high [Ca/Mg] ~ 0.5–1.3 abundance ratios are the most important to discriminate PISN signatures from normal metal-poor star abundances, and have confirmed that no currently observed metal-poor star matches with the PISN abundance [4]. The confirmation of the non-detection, together with a fact that currently no observed luminous supernova has been explained as a PISN event, may indicate that something important is missing from current understanding of stellar physics. Finally, we discuss that qualitatively different stellar evolution, which is against PISN explosion, results from a CO core in which a lowered reaction rate for 12C(α,γ)16O is applied [5]. References [1] K. Takahashi et al., Monthly Notices of the Royal Astronomical Society 456, 1320 (2016). [2] H. Umeda and K. Nomoto, Astrophysical Journal, 565, 385 (2002). [3] A. Heger and S. E. Woosley, Astrophysical Journal, 567, 532 (2002). [4] K. Takahashi et al., in press. [5] K. Takahashi, in prep.

Speaker: Koh Takahashi (Argelander Institute for Astronomy)

Abstract 088_Takahashi.pdf

131 Strong one-neutron emission from two-neutron unbound states in beta decays of r-process nuclei, 86, 87Ga

Beta-delayed one- and two-neutron branching ratios (P1n and P2n) are measured in the decay of 86Ga and 87Ga at the RI-beam Factory at RIKEN Nishina Center using a high-efficiency array of 3He neutron counters (BRIKEN). Two-neutron emission is observed in the decay of 87Ga for the first time. The large P1n value of 87,86Ga compared to P2n is interpreted as a signature of dominating one neutron emission from the two-neutron unbound states in 86,87Ga. Combined shell model and Hauser-Feshbach statistical model calculations are performed in order to interpret the experimental results. The shell model predicts P2n > P1n for 87Ga decay and the observed P1n > P2n is explained successfully only by including the statistical model. This result is the first experimental demonstration that statistical model has to be invoked to predict the decay properties of multi-neutron emitters and that it must be included in the r-process modeling.

Speaker: Rin Yokoyama (University of Tennessee)

Abstract 55_YokoyamaRin.pdf

132 Study of the 2H(p,g)3He cross section at Ep=400-800 keV

The amount of deuterium produced in Big Bang Nucleosynthesis depends sensitively on cosmological parameters such as the baryon energy density and the effective number of neutrino species. The recently improved precision of astronomical measurements of the primordial deuterium abundance calls also for more precise nuclear data. Currently, the precision of the Big Bang abundance prediction of 2H is limited to the uncertainty of 2H destruction in the 2H(p,g)3He reaction. The same nuclear reaction also affects Big Bang production of 7Li and plays a role in solar physics. The present contribution reports on an experimental study of the 2H(p,g)3He cross section at energies of Ep=400-800 keV, recently performed at the HZDR 3 MV Tandetron accelerator in Dresden, Germany.

Speaker: Sebastian Hammer (HZDR Dresden-Rossendorf)

Abstract 73_HammerSebastian.pdf

133 Study of the E_alpha = 395 keV resonance of the 22Ne(alpha,gamma)26Mg reaction at LUNA

The 22Ne(alpha,gamma)26Mg is the competitor of the 22Ne(alpha,n)25Mg in AGB stars. The 22Ne(alpha,n)25Mg is an efficient source of neutrons for s-process in medium masses AGB. There is significant uncertainty in the 22Ne(alpha,gamma)26Mg thermonuclear reaction rate. This has been clearly remarked by the presence of this particular reaction in the COST Action called ChETEC (CA16117) that includes the 22Ne(alpha,gamma)26Mg among the nuclear reactions with great impact on stellar nucleosynthesis. At the energies of the LUNA400kV accelerator a narrow resonance in the 22Ne(alpha,gamma)26Mg reaction has been claimed. This resonance should be at energy E_alpha= 395 keV and it has been studied only with indirect methods leading to a range of possible values for its resonance strength from 10^-9 to 10^-15 eV. At LUNA (Laboratory for Underground Nuclear Astrophysics) this resonance can be studied directly, thanks to a high efficiency setup, composed by a 4\pi-BGO detector and a windowless gas target filled with neon gas enriched in the 22Ne isotope to 99.99%. This setup has been already used in a previous experiment for the study of the 22Ne(p,gamma)23Na reaction, and in April-June 2018 a new measurement campaign will be performed. Thanks to its position inside the Laboratory of Gran Sasso, LUNA already benefits from a reduced background and in particular a factor one thousand for the neutron component. Still this remains the most important source of background in the region of interest for the 22Ne(alpha,gamma)26Mg. A new borated polyethylene shielding will be implemented to reduce the neutron contamination due to the environmental background in order to reduce this contribution by an additional order of magnitude. The poster will show the experimental setup, background, and preliminary data.

Speaker: Antonio Caciolli (Padova University & INFN)

Abstract 120_Caciolli.pdf

134 Systematic isotopic chain investigations of gamma-ray strength functions in the shell model

gamma-ray strength functions are one of the key nuclear physics inputs to constrain (n,gamma) cross-sections for unstable nuclei relevant to different neutron-capture nucleosynthesis processes. This is of particular importance for the r process, where the process flow proceeds through neutron-rich nuclei far from stability. It has been shown that the presence of a low-energy enhancement, seen experimentally in many nuclei including neutron-rich ones could impact the capture cross sections by orders of magnitude, which could in turn severely impact reaction network model predictions. We present a systematic study using large-scale shell model calculations of the low-energy M1 gamma-ray strength function for many isotopic chains in the Nickel mass region. The low-energy enhancement is present in all cases studied, but its strength varies with mass number in systematic ways. We discuss possible explanations for the systematic behaviour, and the implications if this behaviour extends all across the nuclear chart.

Speaker: Jørgen E. Midtbø (University of Oslo)

Abstract Midtbo_abstract_nuclei_in_the_cosmos.pdf

135 The 12C(a,g) Reaction: Most Important, Least Known: Current Status and Prospects for Future Progress

Over the last four decades conflicting data plagued our attempts to deduce the cross section of the 12C(a,g) reaction at low energies and did not allow an accurate extrapo-lation of the astrophysical s-factor to stellar energies. In particular conflicting data did not allow us to chose between the high value (∼80 keVb) and the low value (∼10 keVb) solutions of the E1 s-factor at stellar energies. The so called ”cascade” s-factors were deduced with large uncertainty, as large as a factor of 25. Recent modern measurement of SE1 and SE2 at Stuttgart, were demonstrated [1] to have error bars which are considerably larger than quoted by the authors [2, 3, 4]. In spite of the little progress in measurements of the cross section of the 12C(a,g) reaction, several recent R-Matrix global analyses claim to achieve accuracies of the total s-factor (E1 + E2 + cascade) be-tween 4.5% and 12%. We apply the strict criteria established in the two Seattle workshops [5, 6] to examine current conflicting measurements of the 12C(a,g) reaction. The Seattle workshops addressed similar confusion in measurements of the 7Be(p,g) reaction and the criteria that were established at the Seattle workshops to judge conflicting data can be used as a model for progress in the field. Applying the Seattle workshops criteria we conclude yet a new ambiguity previously not noticed in the value of SE2(300); namely either ∼60 keVb or ∼155 keVb values are consistent with current data [1]. We establish strict requirements on future measurements to allow progress in the field and we point out that such data are within reach using gamma-ray beams of the HIγS facility in the USA or ELI-NP facility in the European Union.

Speaker: Moshe Gai (University of Connecticut)

Abstract 81_GaiMoshe.pdf

136 The HEAT project: Study of hydrogen desorption from carbon targets

HEAT (Hydrogen dEsorption from cArbon Targets) is a new project started in 2018 with the aim of studying the desorption of hydrogen and deuterium contaminations from carbon targets used for Nuclear Astrophysics studies, with special reference to the 12C+12C fusion reaction. 12C+12C fusion is the dominant process during stellar carbon burning and its cross section is a crucial parameter in modern astrophysics, given its strong influence on stellar evolution and nucleosynthesis. In stars, the 12C+12C reaction occurs at center of mass energies well below the Coulomb barrier. This makes the cross section extremely small and challenging to measure. The direct measurements of the 12C+12C cross section performed so far were affected by a strong beam induced background due to the interaction of the carbon beam with hydrogen and deuterium contaminations inside the targets. Due to the ease of forming chemical bonds with carbon, hydrogen is always found in carbon targets. In previous measurements of the 12C+12C cross section attempts were made to desorb hydrogen by heating the samples, but only limited quantitative information is available on the effectiveness of the desorption procedure. The HEAT experiment aims at establishing a reproducible technique for hydrogen desorption from different types of carbon targets. The temperature of the samples will be increased uniformly up to 1200{circ}C through a heating device with a well defined temperature gradient. The contamination level will be measured before and after the desorption process exploiting two independent techniques: Elastic Recoil Detection Analysis and Nuclear Reaction Analysis. The poster will provide a detailed description of the experimental setup presently under construction at Legnaro National Laboratories and the proposed experimental approach.

Speaker: Rosanna Depalo (INFN Padova)

Abstract 172-Depalo.pdf

137 The Impact of Convective Boundary Mixing Uncertainties on pre-Supernovae Structure and Nucleosynthesis

Convection plays a key role in stellar evolution by both transporting energy and mixing composition. Convective mixing alters the internal structure and lengthens significantly the duration of burning stages when it is present. Convective boundary mixing is crucial for the creation of the 13C pocket in low-mass stars (main s-process site) and to determine the extent of convective zones in massive stars. In the case of massive stars, several recent studies have shown the sensitivity of the pre-supernova (pre-SN) structure and their explosion likelihood (e.,g. compactness parameter) to the details of their complex convective history. Despite the importance of convection, these processes are still not well understood and their implementations in 1D stellar evolution codes have large uncertainties and inconstancies due to missing details in the treatment of convective energy transport and turbulent mixing. Hence, it is urgent to improve or even replace the current theory. One longstanding conundrum in all 1D stellar evolution codes is the treatment of convective boundaries. In this work, we illustrate the effects of some convective boundary mixing uncertainties, for example the positioning of the convective boundaries or the strength of convective boundary mixing. We will present the impact of these uncertainties on both the pre-SN structure and the corresponding nucleosynthesis. The goal of this study is to highlight, which aspects of the physics lead to the largest uncertainties in the model prediction as well as which observational tests and 3D hydrodynamic simulations may help constrain convective modelling in 1D stellar evolution models.

Speaker: Etienne Kaiser (Keele University)

Abstract 178-Kaiser.pdf

138 The impact of nuclear physics on the UHECR and neutrino production

The Ultra high energy cosmic rays (UHECRs) interact with the photon fields of the sources in which they are produced and with the background photons of the extragalactic space. We show the experimental situation on photo-nuclear cross section data and demonstrate that the available measurements are sparse in the relevant mass range for the UHECRs. Moreover, the theoretical models that describe the photo-nuclear interactions show differences with respect to the available measurements. We also discuss the impact of different photo-nuclear models in the emitted cosmic-ray nuclei and neutrinos from candidate sources. We also emphasize the need of new inputs from nuclear physics in order to reduce the current uncertainties.

Speaker: Leonel Morejon (DESY)

Abstract 187-Morejon.pdf

139 The Internal and External Ion Sources for the Felsenkeller Underground Accelerator

In order to determine the cross sections of astrophysical reactions at relevant energies pioneering work has been done at LUNA using a 0.4 MV accelerator. The new Felsenkeller laboratory, Germany, will house a 5 MV Pelletron accelerator with stable and intense ion beams in a low background environment to extend on this framework. For this purpose two ion sources are going to be part of the shallow-underground accelerator facility: First an external 134 MC-SNICS cesium sputter source providing carbon beams in tandem mode, secondly an internal radio frequency source for hydrogen and helium beams in single-ended mode. In order to determine the characteristics of these ion sources, overground tests were undertaken at HZDR. This poster will report on long time measurements of the ion current for both ion sources and the beam emittance for the external one.

Speaker: Marcel Grieger (Helmholtz-Zentrum Dresden-Rossendorf)

Abstract 67_GriegerMarcel.pdf

140 The light curves of Tidal Disruption Events: dependence on stellar interior structure

In the past decades, new types of extremely luminous transients were revealed by astronomical surveys. One of them is the so-called tidal disruption event (TDE). When a star approaches a supermassive black hole (BH) within a critical distance (the tidal radius), tidal forces tear the star apart. When the stellar debris falls back onto the BH, the release of the potential energy generates a luminous flare and an observable light variation [1]. According to the generally used Newtonian model [2], the internal structure of the star strongly influences the mass accretion rate of the fallback material, which determines the luminosity. We focus on two stellar objects: a zero age main sequence star and a white dwarf. Density profiles of these objects are calculated by the Lane-Emden polytropic model [3], Chandrasekhar’s theory [4] and the 1D stellar evolution code MESA [5]. Since the observable radiation can provide information about the TDE candidates, our goal is to investigate the spectral energy distributions and the time dependence of the total luminosities. To take into account the real physical configuration of these events, we can study the disc and the wind contribution separately as relevant sources of the radiation [6]. Considering different internal stellar structures, we perform a detailed comparison of TDEs. Our purpose is to determine the type of tidally disrupted star from the quasi-bolometric light curves. References [1] M. Rees, Nature 333, 523–528 (1988). [2] G. Lodato et al., Mon. Not. R. Astron. Soc. 392, 332–340 (2009). [3] G. P. Horedt, Polytropes, Kluwer Academic Publishers (2004). [4] R. Kippenhahn et al., Stellar Structure and Evolution, Springer-Verlag (2012). [5] B. Paxton et al., ApJS 4, 208 (2013). [6] L. E. Strubbe, E. Quataert, Mon. Not. R. Astron. Soc. 400, 2070–2084 (2009).

Speaker: Viktor Szaszkó-Bogár (University of Szeged, Hungary)

Abstract 31_SzaszkoBogarViktor.pdf

141 The LUNA neutron detector array for the direct measurement of the 13C(α,n)16O reaction in its Gamow window

The 13C(α,n)16O reaction is very important in the astrophysical context. This reaction is the dominant neutron source for the synthesis of the main s-process component of heavy elements, taking place in thermally pulsing, low-mass asymptotic giant branch stars. The aim of the current LUNA campaign is the determination of the reaction cross section towards the Gamow window with an accuracy of about 10%. At these low energies (<250 keV) the cross section is of the order of picobarn. Because of this the measurement is taking place in the LNGS Underground Laboratory thanks to the reduction of the neutron background by 3 orders of magnitude compared to the flux on the surface. The experimental setup is composed of 18 low-activity 3He counters embedded in a polyethylene moderator with a geometry optimised for maximal detection efficiency. The target setup includes a high capacity cooling system and allows for quick target changes as well as the possibility to regularly check the target degradation in situ. The poster describes the main features of the experimental setup, the environmental and ion induced backgrounds and presents the determination of the detection efficiency using charged particle induced nuclear reactions, radioactive sources and Geant4 simulations.

Speaker: Laszlo Csedreki (LNGS)

Abstract 146-Csedreki.pdf

142 The muon background in the shallow-underground laboratory Felsenkeller

Muons, which are produced by cosmic rays in the atmosphere, are highly penetrating and are only mitigated by the roughly 50 m of rock above the shallow underground laboratory Felsenkeller in Dresden, Germany. In order to determine the precise flux and angular distribution amount of muons reaching the tunnels of Felsenkeller, a portable muon detector developed and built by the REGARD group [1] was employed. Data have been taken at four positions in Felsenkeller tunnels VIII and IX, where the new 5 MV accelerator will be hosted, and in addition for reference at three positions in Felsenkeller tunnel IV. At each position, seven different orientations of the detector were used to compile a map of the upper hemisphere. The measured muon flux data are compared with a GEANT4 simulation using the known shape and density of the local rock cover.

Speaker: Felix Ludwig (Helmholtz-Zentrum Dresden-Rossendorf)

Abstract 44_LudwigFelix.pdf

143 The neutrino process in self-consistent supernova simulations

Neutrinos play a curcial role for core-collapse supernova explosions and their nucleosynthesis. All flavors of neutrinos are emitted from the hot and dense environment of a collapsing massive star in such tremendous numbers that they not only help to revive the explosion shock wave but also affect the composition of the outer layers of the star that have been chemically enriched during the life of the progenitor star. The neutrinos carry high energies compared to the thermal energies encountered in the stellar mantle and can either be captured on nuclei in an inverse beta decay or induce spallation reactions, i.e. lead to nuclear excitations that decay by particle emission. The effect of these interactions on the final composition of the ejecta is called the nu-process and has been suggested to contribute to the production of 7Li, 11B and 19F as well as 138La and 180Ta. For the first time we have investigated this process with a set neutrino-nucleus cross sections for all nuclei in the reaction network, including multi-particle emission channels and based on experimental data where available. We have explored a range of 1D models of piston driven explosions and for tracers from 2D self-consistent simulations from the Oak-Ridge group. With tracers from a 2D supernova simulation have studied the nu-process in the innermost ejecta where the neutrino fluxes are highest. This also allows us to study the nu-process with neutrino properties that are consistent with the explosion and we find that the time dependent realistic neutrino properties have important effects on nu-process nucleosynthesis and might provide the key to reconcile a low production of 11B with sufficiently high yields of 138La and 180Ta to explain their solar abundances.

Speaker: Andre Sieverding (Technische Universität Darmstadt)

Abstract 66_SieverdingAndre.pdf

144 The neutron capture cross section measurement of the thallium isotopes 203Tl, 204Tl and 205Tl at the n TOF facility at CERN

About half of the elemental abundances between Fe and Bi are produced by the so-called s (slow) process of neutron capture reactions in AGB stars. Of particular importance are some nuclides produced during the s-process which are radioactive, with half-lives from years to Gy, so its decay process competes with the neutron capture chain: these nuclides are known as branching points. The measurement of the neutron capture cross section of these elements is crucial to determine the local abundance pattern around the branching point, which yields information of the s-process stellar environment, such as temperature, neutron density or pressure. 204Tl (T1/2 = 2.78 y) is a very interesting branching point. In the recurrent He-flashes of AGB stars, 204Tl can either β-decay to the s-only nuclide 204Pb or capture another neutron, thus producing 205Tl, which in some stellar environments can decay to 205Pb. On the other hand, neutron capture on 204Pb also yields 205Pb (T1/2 = 1.5 × 10^7 y). Therefore, the value of the capture cross sections of 204Tl, and also of 205Tl, are necessary to determine precisely the primordial 205Pb/204Pb abundances ratio, which could allow one to estimate the time span since the last s-process events that contributed to the elemental composition of the Solar System. In the year 2015, the cross section of the 204Tl (n,γ) reaction was measured for the first time ever employing four C6D6 scintillation detectors in the neutron time-of-flight facility n TOF at CERN. The sample was a 203Tl oxide pellet enriched to 4% in 204Tl. The 204Tl total mass was 9 mg, with a total activity of 160 GBq. Due to the amount of 203Tl in the sample an ancillary measurement of the 203Tl (n,γ) was also necessary in order to improve the accuracy of this reaction cross section. Concerning the 205Tl (n,γ)reaction, its cross section will be measured this year also at n TOF. In this talk we will cover the different aspects of these capture cross section measurements, from the experimental methods to the extraction of the cross section and other important capture reaction parameters, to finally conclude with the application of the results on s-process nucleosynthesis.

Speaker: Adrià Casanovas (Universitat Politecnica de Catalunya)

Abstract 188-Casanovas.pdf

145 The nuclear level density and γ -ray strength function in 64Fe

Neutron-capture rates are critical for models of the astrophysical r-process, yet are difficult to measure directly and often outside the current realm of capability for experimental facilities. Meanwhile, theoretical extrapolations can vary by orders of magnitude even near stability. For example, predicted rates in the Mn-Ga mass region can vary by factors of 10 or more \cite{Liddick}. Nuclei in this region exhibit enhanced collectivity, while an unexpected increase in the $\gamma$-ray decay probability has been observed in stable $^{56,57}$Fe below {$\sim$}4 MeV \cite{Voinov}. The presence of this enhancement, or upbend, has a significant influence on extracted neutron-capture rates. It is unknown how the $\gamma$SF behaves for neutron-rich nuclei. An indirect method known as the $\beta$-Oslo method has been developed to constrain neutron-capture rates \cite{Spyrou} for radioactive nuclei. With the $\beta$-Oslo method, the reaction product is populated in $\beta$-decay, then the nuclear level density and $\gamma$SF are extracted simultaneously. The NLD and $\gamma$SF are then used to constrain the neutron-capture cross section. At the NSCL, we studied the $\beta$-decay of $^{64}$Mn to populate excited states in $^{64}$Fe, a candidate for the upbend in the $\gamma$SF. Gamma rays were recorded with the 4$\pi$ Summing NaI(Tl) (SuN) total absorption spectrometer \cite{Simon}, which is an ideal detector for $\beta$-Oslo analysis. Results will be presented on the extracted $\gamma$SF and level density for $^{64}$Fe.

Speaker: Mallory Smith (NSCL / Michigan State University)

Abstract 189-Smith.pdf

146 The Nuclear Physics Uncertainty on Kilonova Heating Rates and the Role of Fission

The detection of an electromagnetic counterpart to GW170817[1] suggests that r-process elements are produced in neutron star mergers. This electromagnetic counterpart has been modeled as a kilonova, which is a light curve thought to be powered mainly from the radioactive decay of heavy elements formed. We investigate uncertainties in the nuclear physics inputs to kilonova calculations, 1nding that the uncertainty in the total nuclear heating rate is a factor of a few. We examine in particular the role of 1ssion in this heating, and 1nd that while much of the total nuclear heating is driven by beta decay, 1ssion has an important role to play. We identify the nuclei which make the largest contribution to the heating through 1ssion, and we also investigate the population of beta decaying nuclei by way of 1ssion daughter products. References [1] B. P. Abbott et al. [LIGO Scienti1c and Virgo Collaborations], Phys. Rev. Lett. 119, no. 16, 161101 (2017)

Speaker: Yonglin Zhu (North Carolina State University)

Abstract ZHUabstractNIC2018.pdf

147 The rm 19F(alpha,p)22Ne and rm 23Na(p,alpha)20Ne reactions at energies of astrophysical interest via the Trojan Horse Method

19F production and destruction pathways in astrophysic environment is crucial: it is, in fact, the least abundant element in the 12leqAleq56 mass range, and therefore fluorine abundance can me used to test the models. 19F presence is observatively confirmed for low-mass AGB stars (M=2:4Modot), and model failed to reproduce the observed abundance. This fact is probably due to extra mixing problems, but further investigations from a "nuclear'' point of wiew were needed: in AGB environment, in fact, 19F can be destroyed via rm 19F(p,alpha)16O and rm 19F(alpha,p)22Ne. About the second of the two, there are no direct measurement due to the presence of the Coulomb barrier: for a low-mass AGB star, in fact, at the typical range of temperature (rm 2cdot 10^8leq Tleq 4cdot 10^8K) the Gamow window for the reaction lies between 150 and 1200 keV, so far below the barrier (3.81~MeV in this case), while the cross-section measured via direct methods arrives down to 660~keV in the center-of-mass reference frame. For those reason a measurement of the 19F(alpha,p)22Ne was attempted using the Trojan Horse Method, that has proven to be really useful to investigate reactions between charged particles or between charged particles and neutrons in the entrance channel at energies of astrophysical interest. The experiment was performed at Ruder Bovskovic Institute, with a 6~MeV 6Li beam impinging on a 7LiF target, with the aim to trigger the 6Li19F,p22Ne^2H reaction. Using the THM, from the three-body reaction above, we were able to isolate the quasi-free contribution coming from the 19F(alpha,p)22Ne, and the absolute-units cross section was determined. Using the Modified R-matrix formalism, we were also able to determine the resonances strenght, and the evaluated rate has shown to be higher by a factor of almost 5 with respect to what already present in literature. An evaluation of the astrophysical impact of this new reaction rate was also performed adopting the NEWTON code for AGB star nucleosynthesis calculation in order to study fluorine production and destruction. In particular, calculations for three stellar models of 1.5, 3, and 5 Modot and solar metallicity were performed. Another reaction of great interest in AGB nucleosynthesis is the 23Na(p,alpha)20Ne, that is cosidered to have great importance in intermediate-mass AGB stars (M=4:8 M_odot), and could be strongly related to the wide known Na/O anticorrelation in globular clusters. This reaction is also of great importance because it represents, along with the 23Na(p,gamma)24Mg reaction, the turning point between the NeNa and MgAl cycles. Both have the result to fuse hydrogen into helium, and for a mass number 20leqAleq40, both {\rm (p,alpha) and (p,gamma) channels are open at the temperatures typical of H-burning, so those kind of reaction will compete. H-burning in the mass range A\geq20 is important to understand Ne, Na, Mg and Al abundances observed in stars: the relative isotopic abundance depends on the temperature and density conditions inside the H-burning region of a certain star. One of the NeNa and MgAl cycles can be active if the reaction rate branching ratio B_p\alpha/p\gamma=N_Asigma\nu\p\alpha/N_A\sigma\nu\p\gamma) is large enough. About NeNa-cycle, at temperature T~6 cdot 10^6K, 22Ne is entirely transformed in 23Na. An extra production of this element is predicted at temperatures higher than 35 cdot10^6~K, reaching 60% at T~ 60\cdot 10^6~K. This extra production is provided by 20Ne reaction. In the end 23Na starts burning at T\geq 60\cdot 10^6~K. 23Na(p,alpha)^20Ne has not been studied at astrophysical energies with direct methods in the energy range of astrophysical interest. Here the Gamow window lies bwetween 50~keV and 200~keV, while the Coulomb barrier is at 2.57~ MeV. Several states of 24Mg were however studied, via the 23Na(3He,d)24Mg transfer reaction at 20~MeV. Two resonant states at 37~keV and 138~keV were found: the former had a too low cross section to be studied (but uncertainties were reduced by a factor of 515), and the latter is still the bigger source of uncertainties (circa a factor of 12) in the temperature region near T~70\cdot 10^6~K. From those facts is clear how even a slight reduction of the uncertainties is critical. For the 23Na(p,alpha)20Ne reaction, the Trojan Horse Metod was applied using the brand new 23Na beam delivered at Laboratori Nazionali del Sud. The beam collided with a CD_2 target, with the aim to induce the 23Na(d,alpha,20Ne) three-body reaction. We were able to select data coming from the quasi-free contribution of the reaction of interest. An evaluation of the arbitrary-units differential cross-section at the energies of astrophysical interest was also performed. This energy interval corresponds to 50leq E leq200 keV in the range of temperature proper of intermediate-mass AGB stars (20cdot 10^6leq Tleq 80cdot 10^6~K) . References [1] Indelicato, I., La Cognata, M., Spitaleri, C., et al., Apj, 845 (2017) [2] Pizzone, R. G., D’Agata G., La Cognata M., Indelicato I., et al., Apj, 836 (2017) [3] D’Agata, G., Pizzone, R. G., La Cognata, M., Indelicato, I., et al., submitted (2018) [4] Ugalde, C., Azuma, R. E., Coutre, A., et al., Phys.Rev.C, 77 (2008) [5] Ventura, P. and D’Antona, F., MNRAS, 410 (2011) [6] Mowlavi, N., A&A, 344, (1999) [7] Hale, S.E., Champagne, A.E., Iliadis, C., et al , Phys.Rev.C, 70 (2004)

Speaker: Giuseppe D'Agata (INFN - LNS)

Abstract 9_DAgataGiuseppe.pdf

148 The s-process nucleosynthesis in low mass stars: impact of the uncertainties in the nuclear physics determined by Monte Carlo variations

We investigated the impact of uncertainties in neutron-capture and weak reactions (on heavy elements) on the s-process nucleosynthesis in low-mass stars using a Monte-Carlo based approach. We performed extensive nuclear reaction network calculations that include newly evaluated temperature-dependent upper and lower limits for the individual reaction rates. Consistent with previous studies, we found that beta-decay rate uncertainties affect only a few nuclides near s-process branchings, whereas most of the uncertainty in the final abundances is caused by uncertainties in neutron capture rates, either directly producing or destroying the nuclide of interest. Combined total nuclear uncertainties due to reactions on heavy elements are in general less than 50%.

Speaker: Gabriele Cescutti (INAF Trieste)

Abstract 163-Cescutti.pdf

149 The Stellar 72Ge(n,g) Cross Section: A First Measurement at n_TOF

The slow neutron capture process (s-process) is responsible for producing about half of the elemental abundances heavier than iron in the universe. Neutron capture cross sections on stable isotopes are a key nuclear physics input for s-process studies. The 72Ge(n,g) Maxwellian Average Cross Section (MACS) has an important influence on production of isotopes between Ge and Zr in the s-process in massive stars [1] and so far only theoretical estimations are available [2]. An experiment was carried out at the neutron time-of-flight facility n_TOF [3] at CERN to measure the 72Ge(n,g) reaction for the first time at stellar neutron energies. At n_TOF, neutrons over a large energy range (few meV to several GeV) are produced by spallation reactions of a highly energetic (20 GeV/c), pulsed proton beam impinging on a massive Pb target. The capture measurement was performed using an enriched 72GeO2 sample at a distance of 184 m from the spallation target (Experimental Area 1), which allows a measurement with high neutron energy resolution. The prompt gamma rays produced after neutron capture were detected with a set of liquid scintillation detectors (C6D6), which met the experimental requirements of low neutron sensitivity [4]. The neutron capture yield is derived from the counting spectra taking into account the neutron flux and the gamma-ray detection efficiency using the Pulse Height Weighting Technique [5]. The experiment, data analysis and preliminary results will be presented.

Speaker: Mirco Dietz (University of Edinburgh)

Abstract 151_Dietz.pdf

150 The Study of 29Si(p,g)30P and Its Relevance to Classical Nova Nucleosynthesis

A classical nova is a stellar explosion occurring between the white dwarf and the main sequence companion star of a binary system, and while it is suspected that these explosions are responsible for the galactic production of rare nuclear species, a number of open questions about their dynamics remain unanswered. Some knowledge of the nature of classical novae can be gained using traditional means in the observatory, but by studying presolar grains of nova origin, one can learn more about classical novae in the laboratory as well. These grains, minute traces of ejected material produced in stellar explosions and later incorporated into meteorites, carry isotopic signatures of the processes that created them. A collection of grains with a putative classical nova origin have been identified in recent years. By comparing the isotopic abundances from these grain measurements to the results of computational models of nova explosions, our understanding of these fascinating events can be tested and improved. Discrepancies between grain isotopic ratios and those predicted by simulations complicate the efficacy of this strategy however. It will be shown that poorly constrained reaction rates substantially contribute to these discrepancies, using the effect of 29Si(p,g)30P rate uncertainties on the d(29Si/28Si) ratio as an illustrative case. This motivated the study of several low-energy resonances in the 29Si(p,g)30P reaction undertaken at the Laboratory for Experimental Nuclear Astrophysics (LENA). The experimental and analytical methods and challenges involved in these measurements will be discussed at length, followed by a presentation of results and preliminary understanding of their significance.

Speaker: Lori Downen (University of North Carolina)

Abstract 193-Downen.pdf

151 Thermodynamic instabilities in compact stars

We investigate the possible thermodynamic instability in a warm and dense nuclear medium where a phase transition from nucleonic matter to resonance-dominated Delta-matter can take place. Such a phase transition is characterized by both mechanical instability (fluctuations on the baryon density) and by chemical-diffusive instability (fluctuations on the isospin concentration) in asymmetric nuclear matter. Similarly to the liquid-gas phase transition, the nucleonic and the Delta-matter phase have a different isospin density in the mixed phase. In the liquid-gas phase transition, the process of producing a larger neutron excess in the gas phase is referred to as isospin fractionation. A similar effects can occur in the nucleon-Delta matter phase transition due essentially to a Delta- excess in the Delta-matter phase in asymmetric nuclear matter. In this context we also discuss the relevance of Delta-isobar and hyperon degrees of freedom in the bulk properties of the cold neutron stars and in the protoneutron stars at fixed entropy per baryon, in the presence and in the absence of trapped neutrinos.

Speaker: Gianpiero Gervino (INFN Torino)

Abstract 177_Lavagno.pdf

152 Towards a better description of neutrino opacity in hot and dense matter

An accurate description of neutrino interaction in hot and dense nuclear matter is important to dynamics of core-collapse supernova (CCSN) explosion and nucleosynthesis in CCSN as well as neutron star mergers (NSMs). In this work, improvements regarding neutrino opacity calculations in different aspects are studied. Firstly, higher order weak interaction terms like weak magnetism and pseudo-scalar coupling are included with full form factor dependence. Secondly, nucleon energy shifts in low-density nuclear matter have been obtained by using virial expansion and the Brueckner-Hartree-Fock (BHF) approach based on chiral EFT interactions, which can lead to a relatively accurate charged current neutrino opacity in the neutrino sphere in CCSNe. Thirdly, nucleon-nucleon bremsstrahlung processes, which are believed to be important at relatively high density region for neutrino transport, have been revisited using in-medium T-matrix formalism. RPA effects can be further taken into account on top of the above improvements.

Speaker: Gang Guo (GSI, Germany)

Abstract 175-GGuo.pdf

153 Two-body description for the radiative capture reaction 6Li (p,gamma)7Be

The 6Li abundance measured in the atmosphere of metal-poor stars is three orders of magnitude larger than predicted by the theory of Standard Big Bang Nucleosythesis (SBBN) predictions [1]. Even if the results of the astronomical measurements are still under debate [2-4], the knowledge of the cross section (or astrophysical S-factor) of the reactions that contribute to determine the 6Li abundance is fundamental in order to distinguish between different explanations. Among these reactions, the radiative capture 6Li(p,gamma)7Be plays an important role. Although this reaction was extensively studied experimentally [5-8], very large uncertainties in the S-factor in the BBN energies (50-400 keV) are still present. A recent work [9] pointed out the presence of a possible resonance in the BBN energy window, that reduces the S-factor at zero energy. In order to solve this puzzle, a new campaign of measurement was performed by the LUNA collaboration. From the theoretical side many studies were performed using different approaches and inputs, like a two-body a phenomenological potential [10], an optical potential [11], a cluster model [12] and the Gamow shell model [13]. In this work, we try to improve the model used in Ref. [10]. We treat the problem as a two-body problem, using phenomenological potentials to predict the S-factor. We fit the parameters of our potentials in order to reproduce the elastic scattering data of 6Li(p,p)6Li and the bound states properties of the 7Be. Solving the two-body Schroedinger equation, we evaluate the wave functions for the scattering and the bound states, which we use to predict the S-factor of the radiative capture reaction. The calculated S-factor can reproduce the energy behavior, but in order to agree with the experimental data we need to multiply the results by a spectroscopic factor. This is not surprisingly, since in this simple study we have neglected the internal structure of both 6Li and 7Be. The final results are in nice agreement with the available experimental data at stellar energies. Bibliography [1] M. Asplund et al., Astrophys. J. {\bf{644}}, 229 (2006). [2] R. Cayrel et al., Astron. Astrophys. 473, L37 (2007). [3] A. E. Garcia Perez et al.,Astron. Astrophys. 504, 213 (2009). [4] K. Lind et al., Astron. Astrophys. 554, A96 (2013). [5] S. Bashkin and R. R. Carlson, Phys. Rev. Lett. 97, 5 (1995). [6] Z. E. Switkowski et al., Nucl. Phys. A 331, 50 (1979). [7] F. E. Cecil et al., Nucl. Phys. A 539, 75 (1992). [8] R. M. Prior et al., Phys. Rev. C 70, 055801 (2004). [9] J.J. He et al., Phys. Lett. B 725, 287 (2013). [10]S. B. Dubovichenko et al., Phys. Atom. Nucl. 74, 1013 (2011). [11]F. C. Barker, Aust. J. Phys. 33, 159 (1980). [12]K. Arai, D. Baye, and P. Descouvemont, Nucl. Phys. A 699, 963(2002). [13]G. X. Dong et al., J. Phys. G: Nucl. Part. Phys. 44, 045201 (2017).

Speaker: Alex Gnech (Gran Sasso Science Institute)

Abstract 42_GnechAlex.pdf

154 Volatile Element Chemistry in the Solar Nebula - Revisited 40 Years Later

The relative abundances of volatile to refractory elements are easily affected by condensation and evaporation and therefore thermochemical equilibrium calculations are important to quantitatively evaluate fractionations between gases and solids in astronomical environments. Fegley and Lewis (1980 Icarus) computed condensation temperatures for P, F, Cl, Na, and K in the solar nebula using Cameron (1973) solar abundances. They also calculated chemical equilibrium abundances of gases and solids as a function of pressure and temperature. Lodders (2003 ApJ) and Schaefer & Fegley (2010 in Principles and Perspectives in Cosmochemistry, Springer) updated this work as new thermodynamic data (e.g., Lodders 1999,2004 J Phys Chem Ref Data) and better solar abundances became available. Several recent advances in the past decade led us to revisit and extend our earlier work, e.g., (1) new thermodynamic data on halogen-bearing and phosphorus-bearing minerals, (2) new chemical analyses and mineralogical studies of halogens and their host phases in terrestrial and extraterrestrial samples, and (3) renewed interest in the 36Cl-36S and 129I-129Xe systems. The results of our chemical equilibrium calculations confirm those of Schaefer and Fegley (2010) for fluorine and chlorine. At complete chemical equilibrium (0.0001 bar total P) fluorine condenses at about 713 K (50 percent) and chlorine condenses at about 400 K (50 percent). Our results for bromine and iodine also revise our earlier work (Fegley and Lewis 1980, Lodders 2003) due to newer thermodynamic data for their host phases. Finally we also show how kinetic inhibition of condensate formation in the solar nebula (e.g., see Fegley 1988 LPI Tech Report 88-04) affects halogen condensation temperatures. This work was supported by grant NSF-AST 1517541 from the NSF Astronomy Program.

Speaker: Bruce Fegley (Washington University)

Abstract Fegley_&_Lodders_2018_Volatile_element_chemistry_in_the_solar_nebula_-_revisited_40_years_later.pdf

155 Weak interference between the 1^- states in the vicinity of alpha-particle threshold of 16O

The subthreshold 1^-_1 state at an excitation energy E_x = 7.12 MeV in 16O has been believed to enhance the astrophysical S-factor for 12C(alpha,gamma_0)16O. The enhancement seems to originate from strong interference between 1^-_1 and 1^-_2 (E_x ~ 9.6 MeV) in the vicinity of the alpha-particle threshold. However, the weak interference between two states and a resulting small E1 S-factor are exemplified with R-matrix theory in this presentation. In my previous reports [1], I have predicted the small E1 S-factor at E_c.m.= 300 keV from the potential model, because non-absorptive scattering results in weak coupling between shell and cluster structure in 16O. In the present example, I utilize the previous results to estimate the reduced alpha-particle width of 1^-_1 and 1^-_2. In addition, the formal parameters in R-matrix are obtained from an exact expression, including a higher-order correction, because it has been reported that the resonance parameters for 1^-_2 are not appropriately treated in the linear approximation. This correction ensures that the R-matrix calculation corresponds to the experimental data. In the calculation [2], a large energy shift for the pole of 1^-_2 is expected from the alpha+12C cluster structure in 16O. The resultant energy of the 1^-_2 pole is found to be located in the vicinity of 1^-_1. This proximity of the poles suppresses their interference, and it consequently makes the small E1 S-factor below the barrier (Figure 1). The corresponding results of the \beta-delayed alpha-particle spectrum of 16N and the calculated p-wave phase shift of alpha+12C elastic scattering are consistent with the previous experimental results. The experimental alpha-particle width of 1^-_2 is also reproduced by the present example. It would therefore be possible in the R-matrix method that the E1 S-factor is reduced from the enhanced value currently expected. At the same time, the reaction rates of 12C(alpha,gamma)16O are expected to be obtained from the direct-capture component, rather than compound nucleus mechanisms. [1] M. Katsuma, Proc. Nuclei in the Cosmos XIV, JPS Conf. Proc. 14 (2017) 021009; M. Katsuma, Phys. Rev. C78, 034606 (2008); ibid. 81 (2010) 067603; Astrophys. J. 745 (2012) 192; PoS(NIC XIII) (2015) 106. [2] M. Katsuma, arXiv:1701.02848 [nucl-th].

Speaker: Masahiko Katsuma (Osaka City University)

Abstract 116_Katsuma.pdf

156 Women scientists who made nuclear astrophysics

Female role models reduce the impact on women of “stereotype threat” [1], i.e., of “being at risk of confirming, as a self-characteristic, a negative stereotype about one’s social group” [2]. This can lead women scientists to underperform or to leave their scientific career because of negative stereotypes such as that they are not as talented or interested in science as men. Sadly, history rarely provides role models for women scientists; instead it often renders these women invisible [3]. In response to this situation, we present a selection of twelve outstanding women who helped develop nuclear astrophysics - some famous, some less so. The final aim is to produce a calendar, which will be translated into several languages. This project is developed as part of the COST Action ChETEC (chetec.eu, CA16117). [1] See, e.g., “Delusion of gender”, Cordelia Fine, 2010, W.W. Norton and Co. ISBN 0-393-06838-2, page 36 and references therein. [2] Steele & Aronson, 1995, “Stereotype threat and the intellectual test performance of African-Americans”, Journal of Personality and Social Psychology, 69, 797-811. [3] “...by moving a woman to the background, by making her disappear com- pletely from the narrative, by minimising her involvement, by fiddling with the story [...], by diminishing or stealing her work, by confining her to the role of “wife of ” or “sister of ” [or “assistant of ”], auto-erasure” (source http://www.cafebabel.co.uk/society/article/georgette-sand-when-history- makes-women-invisible.html).

Speaker: Maria Lugaro (Konkoly Observatory)

Abstract 23_LugaroMaria.pdf

157 Bus to hotels

Wednesday, 27 June

Cosmology and big bang nucleosynthesis

Convener: Oscar Straniero (INAF - OATe)

158 Experimental Challenge to the Cosmological Li Problem in the Big-Bang Model

The primordial nucleosynthesis (BBN) right after the big bang is one of the key elements that support the big bang model. The BBN is well known that it produced primarily light elements, and explains reasonably most of the elemental abundances. However, there remain some interesting and serious questions. One is the over production problem of 7 Li, called the cosmological Li problem. The BBN simulations using recent detailed micro-wave background measurements explain most light elements including D, 4 He, etc, but the 7 Li abundance is over predicted roughly by a factor of three. The problem resides either in nuclear reaction cross sections which are not know well, unknown physics, or astronomical observations. Recently, there have been significant progresses reported on nuclear cross sections [1, 2, 3], especially for the destruction process of 7 Be, which is considered to be the main producer of 7Li in BBN. The primordial 7 Li is considered to have been produced mostly by the electron capture of 7 Be in the late stage of BBN. Thus, the question for nuclear physics side is whether 7Be is overproduced or less destructed in the BBN model [1]. The least investigated reaction was 7 Be(n,α)7 He. Direct measurements were reported by measuring the 7Be(n,α) reaction with neutron beams for the s-wave component [2], and by the time-reverse reaction 4 He(α ,n)7Be for the p-wave component [3]. In total, the 7Be(n,α)7He cross sections has been identified to be not large enough to destroy 7 Li to explain the overproduction of 7 Li in BBN. This conclusion is supported by the following efforts such as the experiments using the Trojan Horse method. I will extend my discussion on other possible destruction reactions of 7 Be, which are also being investigated. One is to revisit the main destruction reaction 7 Be(n,p)7 Li. Nuclear reactions of 7Be with t and 3 He are also under investigation, although these reactions seem less probable. Another interesting question for the BBN is the heavy element synthesis. This would affect the first star generation. Some possible reaction channels that lead to production of the CNO elements will be also touched in the talk. References [1] S.Q. Hou, J.J. He, S. Kubono, and Y.S. Chen, Phys. Rev. C 91 (2015) 055802. [2] M. Barbagallo et al., Phys. Rev. Lett. 117 (2016) 152701. [3] T. Kawabata, S. Kubono et al., Phys. Rev. Lett. 118 (2017) 052701.

Speaker: Shigeru Kubono (RIKEN Nishina Center)

Abstract ID082_Kubono.pdf

Slides Kubono_NIC2018_public_version.pdf

159 Connecting Nuclear Astrophysics to Cosmological Structure Formation

Galactic chemical evolution (GCE) is a multidisciplinary topic that involves nuclear physics, stellar evolution, galaxy evolution, and cosmology. Observations, experiments, and theories need to work together in order to build a comprehensive understanding of how the chemical elements synthesized in astronomical events are spread inside and around galaxies and recycled into new generations of stars. In this talk, I will present our efforts to create permanent connections between the different fields of research involved in GCE, highlight the impact of nuclear physics uncertainties on GCE predictions, and describe the challenges of using chemical abundances to trace the formation and evolution of dwarf galaxies in the early universe. I will also discuss the implication of the first gravitational wave detection of a neutron star merger event (GW170817, Abbott et al. 2017) on the evolution of r-process elements in the Milky Way from a GCE perspective.

Speaker: Benoit Côté (Konkoly Observatory)

Abstract ID_104_Cote.pdf

Slides Cote_NIC_Italy_2018.pdf

160 7Be(n,p) cross section measurement for the Cosmological Lithium Problem at the n_TOF facility at CERN

Big Bang Nucleosynthesis (BBN) theory predicts the abundances of the light elements D, 3He, 4He and 7Li produced in the early universe. The primordial abundances of D, 3He and 4He inferred from observational data are in good agreement with predictions, however, the BBN theory overestimates the primordial 7Li abundance by about a factor of three with respect to the observations in metal poor halo stars [1]. This discrepancy is known as “Cosmological Lithium Problem” (CLiP). Since primordial 7Li is produced mainly by the decay of 7Be, reducing the amount of 7Be surviving the BBN phase, reduces the primordial 7Li. The two principal reactions responsible of the destruction of 7Be via neutron reactions are: the 7Be(n,p)7Li, providing 97% destruction of 7Be and the 7Be(n,a)4He, responsible of 2.5%. The (n,a) reaction has already been studied at the n_TOF facility at CERN, where its cross section has been found too low to solve the CliP[2]. Various measurements have excluded also a significant effect on the CLiP of charged particle induced reactions on 7Be, so the only possibility left to find a Nuclear physics solution to the problem is the (n,p) reaction. Despite the importance of this reaction in BBN, there is a lack of cross section data. Taking advantage of the innovative features of the second experimental area at n_TOF facility at CERN[3][4], e.g. the very high instantaneous flux, the wide energy range and the low background conditions, an accurate measurement of 7Be(n,p)7Li cross section has been recently performed at n_TOF with a pure 7Be target produced by implantation of a 7Be beam at ISOLDE. The experimental procedure, the set-up used in the measurement and the results will be presented in this talk. References [1] Martin Asplund et al., The Astrophysical Journal {644}(2006). [2] M. Barbagallo et al., Phys. Rev. Lett. {117} (2016). [3] M. Sabatè-Gilarte et al., Eur. Phys. J. A {53}(2017)210. [4] C.Weiss et al., NIM A {799}(2015)90

Speaker: Lucia Anna Damone (INFN Bari)

Abstract 4_Damone.pdf

Slides Damone_NIC2018_public_version.pdf

161 Cross section measurements of the 7Be(n,p)7Li and the 7Be(n,α)4He reactions covering the Big-Bang nucleosynthesis energy range by the Trojan Horse method at CRIB

It is still an open question that the prediction of the primordial 7Li abundance by the standard Big-Bang Nucleosynthesis (BBN) model is about 3 times larger than the observation, the so-called cosmological 7Li problem. Since the 7Li abundance strongly depends on the 7Be production and destruction rate, those of the main destruction processes 7Be(n,p)7Li and 7Be(n,α)4He need to be determined in the BBN energy range. In spite of the several recent experimental progresses, there are still some uncertainties and ambiguities at the most relevant energies; the 7Be(n,p1)7Li∗ channel, the transition to the first excited state of 7Li has never been taken into account; several new studies on the 7Be(n,α)4He yet lack in data directly reaching the BBN energies. We have performed indirect measurements of both of these reactions by the Trojan Horse Method (THM). The experiments were performed at the INFN-LNL in collaboration with the INFN-LNS nuclear astrophysics group, and at the Center-for-Nuclear-Study Radioactive Ion Beam (CRIB) separator located at RIKEN. We will present the results of the latter experiment. The experimental setup consisted of two parallel-plate avalanche counters to track the 7Be RI beam bombarding a CD2 target, and 6 sets of ∆E-E position-sensitive silicon telescopes to observe the 7Be(d,7Lip)1H and 7Be(d,αα)1H reactions in inverse kinematics, which allowed us to approach the 7Be(n,p)7Li and 7Be(n,α)4He reactions in quasi-free kinematics, respectively. The contributions of the 7Be(n, p0)7Li and the 7Be(n,p1)7Li∗ reactions were extracted by Gaussian fitting to the 3-body Q-value spectrum for Ec.m.∼0–2 MeV. We will discuss the consistency of the present data with the previous ones taking into account resonance structures, also showing new information around the BBN energies including possible 7Be(n,p1)7Li∗ contributions with reliable error evaluations.

Speaker: Seiya Hayakawa (Center for Nuclear Study, University of Tokyo)

Abstract 124_Hayakawa.pdf

162 The cosmologically relevant 7Be(n,alpha)4He reaction in view of the recent THM investigations

The role of the unstable 7Be during the early epoch of the Big Bang Nucleosynthesis is currently matter of study in view of the long-standing 7Li cosmological problem [1]. Recently, the Trojan Horse Method (THM) [2] have been applied for measuring the cross section of the (n,alpha) reaction channel on 7Be by means of charge-symmetry hypothesis applied to the previous 7Li(p,alpha)4He THM data corrected for Coulomb effects. The deduced 7Be(n,alpha)4He data overlap with the Big Bang nucleosynthesis energies and the deduced reaction rate allows us to evaluate the corresponding cosmological implications [3]. References [1] C. Bertulani & T. Kajino, Progress in Particle and Nuclear Physics 89, 56 (2016) [2] R.E. Tribble et al., Report on Progress Physics 77, 106901 (2014) [3] L. Lamia et al., The Astrophysical Journal 850, 175 (2017)

Speaker: Livio Lamia (University of Catania & INFN)

Abstract 016_Lamia.pdf

11:00 Coffee break

Techniques, tools and facilities for nuclear astrophysics

Convener: Manoel Couder (University of Notre Dame)

163 Direct Measurements Using Stable Beams

Many stellar burning phases are dominated by thermonuclear reactions involving stable nuclei. Prominent examples include hydrostatic hydrogen and helium burning in low-mass stars, massive stars, and thermally pulsing asymptotic giant branch stars. The nuclear reaction cross sections involved are very small and thus successful measurements require sophisticated equipment and data analysis techniques. This talk provides an overview of recent experimental improvements. Implications for globular clusters, presolar grains, and galactic radioactivity will be discussed.

Speaker: Christian Iliadias (University of North Carolina)

Abstract ID_209_liadis.pdf

164 Neutron Induced Reactions in Astrophysics

Neutron induced reactions play an important role in the formation of elements heavier than iron. In particular, neutron capture cross sections are a key nuclear physics input to predict abundances produced in the slow neutron capture process (s-process), which is responsible for about half of the heavy element abundances. Stellar models require cross section data on stable isotopes with accuracies of only a few percent, as well as experimental data on some radioactive isotopes, which may act as branching points in the s-process. Also for lighter mass isotopes, neutron induced reactions may play a crucial role, for example for the abundance of the cosmic gamma ray emitter 26Al, which is destroyed by 26Al(n,p) and 26Al(n,alpha) reactions. An experimental determination of these reactions is often challenging as only small amounts of sample material may be available (typically the case for radioactive species), or the reaction product may be hard to distinguish from background signals due to electronic noise or neutron scattering. I will present techniques for measuring neutron induced reaction cross sections, recent results and their importance to stellar nucleosynthesis. I will also talk about experimental advances and future possibilities for measurements on radioactive nuclei.

Speaker: Claudia Lederer-Woods (University of Edinburgh)

Abstract Lederer_Woods_abstractNIC2018.pdf

Slides LedererWoods_NIC2018_public_version.pdf

165 Nuclear AstroPhysics at ELI-NP: preliminary experiments with ELISSA detector

The Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility, under construction in Magurele near Bucharest in Romania, will provide high-intensity and high-resolution gamma ray beams that can be used to address hotly debated problems in nuclear astrophysics, such as the accurate measurements of the cross sections of several reactions important for the astrophysical p-process, Big Bang Nucleosynthesis and supernova explosion. For this purpose, a silicon strip detector array (named ELISSA) will be realized in a common effort by ELI-NP and Laboratori Nazionali del Sud (INFN-LNS, Catania, Italy), in order to measure excitation functions and angular distributions over a wide energy and angular range. We performed very accurate GEANT4 simulations in order to optimize resolution, detection efficiency, compactness, granularity, possibility of particle identification and costs. According to our simulations, the final design of ELISSA will be a very compact barrel configuration, leaving open the possibility in the future to pair a neutron detector with the array. The kinematical identification will allow to separate the reaction of interest from others thanks to the good expected angular and energy resolutions. An experimental campaign is ongoing in order to test the feasibility of the future study at ELI-NP. With this aim, an experiment has been approved at INFN-LNS in order to measure the 19F(p,alpha_pi)16O reaction at astrophysical energies using a prototype of the ELISSA array. Indeed, 19F synthesis is believed to take place in the H-He intershell region of AGB stars but current models fail to explain the high F abundances found in the low-mass AGB stars. Despite the 19F(p,alpha)16O is the main destruction channel and its reaction rate is determined by the sum over the rate for the (p,alpha_0), (p,alpha_pi) and the (p,alpha_gamma) channels, most of the existing measurements refer only to the 19F(p,alpha_0)16O channel, while very little experimental info is available for the (p,alpha_pi) and (p,alpha_gamma) rates at very low energies. Our simulations show that ELISSA will ensure the energy separation between the different channels and the kinematical identification of the outgoing reactions for which a good resolution is a crucial parameter. Moreover, an exploratory experiment to measure the 7Li gamma,3H4He reaction has been performed at High Intensity Gamma Source (HIgammaS). The reaction is of interest for the longstanding "Cosmological Li problem" and for verifying several recent theoretical predictions. The preliminary results of the experiment will be presented. The good preliminary results of our tests and simulations allows us to say that the ELISSA detector will be very suitable for nuclear astrophysics experiment with the upcoming gamma ray beam at the ELI-NP facility.

Speaker: Giovanni Luca Guardo (INFN - LNS)

Abstract 063_Guardo.pdf

Slides Guardo_NIC2018_public_version.pdf

166 The proton-capture campaign at the GSI storage rings

Radiative proton-capture reactions play a crucial role in explosive nucleosynthesis. In the corresponding stellar scenarios, e.g. supernovae or X-ray bursts, the nuclear reaction flow predominantly proceeds in the domain of radioactive nuclei, making reactions studies in the laboratory challenging. The most promising approach to cross section measurements on radionuclides is to prepare them in inverse kinematics at a rare ion beam facility like GSI/FAIR. After production at higher energies in the fragment separator the secondary beam can be injected into the ESR storage ring, where it is decelerated to the Gamow window and used efficiently for reaction studies. In this contribution the experimental method will be outlined with a focus on the challenges of particle detection in ultra-high vacuum and the storage of low-energy ions in a ring. Additionally, an extended overview of the proton-capture studies at the ESR will be given. This will include a discussion of results for the 96Ru(p,g) pilot experiment, the ongoing analysis of the 124Xe(p,g) reaction as well as the technical improvements achieved in the meantime. Finally, an outlook to future experiments will be given. Here, special emphasis will be put on the CRYRING@ESR facility, which is designed for the storage of heavy ions between several 100 keV/u and up to 10 MeV/u making it the perfect device to study reactions in the Gamow window.

Speaker: Jan Glorius (GSI Helmholtzzentrum für Schwerionenforschung)

Abstract 008_Glorius.pdf

167 Study on explosive nuclear synthesis with low-energy RI beams at CRIB

Astrophysical reactions involving radioactive isotopes (RI) are of importance for the stellar energy generation and nucleosynthesis especially in explosive stellar environments, such as X-ray bursts, core-collapse supernovae, big-bang and supermassive metal-poor stars. In spite of the essential difficulties in the experimental evaluation of those reaction rates, there are several successful approaches to study them. The experiments at the low-energy RI beam separator CRIB (CNS Radioisotope Beam Separator), operated by Center for Nuclear Study (CNS), the University of Tokyo, are introduced as examples of such studies. A striking method to study nuclear resonances in unstable nuclei is the proton/alpha resonant scattering with the thick target method in inverse kinematics. Many measurements have been performed at CRIB [1–4], mainly to study properties of resonances which may affect astrophysical reaction rates. With the measurement of 30S+alpha resonant scattering [4], we evaluated the 30S(alpha, p) reaction rate, which produces a considerable effect on the energy generation of X-ray bursts. The latest application of that method is the proton resonant scattering on an isomer-enriched 26Al RI beam, to study the destruction process of 26Al, which may reduce the production rate of cosmic 26Al gamma-rays. Indirect measurements of relevant astrophysical reactions have also been performed at CRIB. The world's 1st Trojan-horse-method experiment with an RI beam was performed at CRIB by an international collaboration including the INFN-LNS group. Measuring quasi-free 18F(d, n alpha) reaction, the low-temperature 18F(p, alpha) reaction S-factor was experimentally determined for the 1rst time [5]. Another recent Trojan-horse measurement at CRIB was to determine 7Be(n, p) and (n, alpha) reaction rates, which can be relevant for the cosmological 7Li abundance problem. We have performed a measurement of those reactions with the 7Be beam at CRIB, covering the temperature range of the big-bang nucleosynthesis. References [1] H. Yamaguchi et al., Phys. Rev. C 87 (2013) 034306. [2] J.J. He et al., Phys. Rev. C 88 (2013) 012801(R). [3] H. Yamaguchi et al., Phys. Lett. B 766 (2017) 11. [4] D. Kahl et al., Phys. Rev. C 97 (2018) 015802. [5] S. Cherubini et al., Phys. Rev. C 92 (2015) 015805.

Speaker: Hidetoshi Yamaguchi (Center for Nuclear Study, University of Tokyo)

Abstract 018_Yamaguchi.pdf

Slides Yamaguchi_NIC2018_public_version.pdf

13:15 Lunch

Excursion

Thursday, 28 June

Solar system

Convener: Nikos Prantzos (Institut d'Astrophysique de Paris)

168 The chemical composition of the Solar System

The stage for studying element and isotopic distributions with the goal to understand the origin of the chemical elements was set about a century ago when it was already recognized that meteorite compositions can provide clues, and when Russell (1929) did the first comprehensive quantitative analyses of elements on the photosphere and found that abundances of non-volatile elements in meteorites compared reasonably well. By the 1950s, improvements in detection sensitivities and quantitative analysis for solar and stellar spectroscopy, and also for analytical chemistry of numerous meteorite classes gave abundance data that served as testbed for nucleosynthesis models. By now, only 68 of 83 elements have been analyzed in the sun because issues with line strengths, number of lines, their accessibility in the spectrum and blending hamper measurements of all elements in the solar photosphere. The use of the CI-chondrites (carbonaceous chondrites of the Ivuna type) as solar system standard rocks for non-volatile elements was encouraged by Urey (1952) but it took until the 1970s to settle which type of chondritic meteorite is best suited to derive solar system abundances. Among primitive meteorites, the CI-chondrites are least affected by chemical volatility fractionations. About 40 elements have well-determined abundances in the sun and CI-chondrites that match quite well (except for very volatile elements H,C,N,O with gaseous compounds, and the noble gases). On the downside, only 5 CI chondrites were collected after they fell (out of more than 1,000 observed falls), and less than 25 kg total of them is left for study. Optimal CI chondritic abundances require multiple well-determined elemental analysis, and recently a surge of new elemental and isotopic measurements provided improvements, but also some problems. The abundances for all 83 naturally occurring elements and their isotopes can be evaluated statistically and, for quality-control, be compared to abundance systematics in other astronomical objects for elements with very similar chemistries and/or nucleosynthesis origins. Updates to our previous evaluations of CI-chondrite compositions for the solar system abundances will be presented and compared to recent photospheric data. Work supported by NSF AST1517541.

Speaker: Katharina Lodders (Washington University)

Abstract ID_100_Lodders.pdf

Slides Lodders_NIC2018_public_version.pdf

169 Nucleosynthetic fingerprints in meteorites and planets

During the past decade, it has been well established that virtually each planetary body in our solar system carries its own distinct nucleosynthetic isotope compositions. The variable compositions represent the heterogeneous distribution of presolar nm-to-µm size dust grains in our Solar System. While they were destroyed in most planetary bodies, primitive meteorites preserved these dust grains, which formed around evolved stars or in ejecta of stellar explosions. These grains still carry the extreme isotope compositions of their production sites. Primitive meteorites also contain mm-to-cm sized refractory inclusions. They show smaller isotopic variations in neutron-rich isotopes (e.g., 48Ca, 50Ti and 96Zr). Their subdued compositions compared to presolar dust results from mixing of material within the solar system. The smallest variations are observed on the largest scale: bulk meteorites and samples from terrestrial planets preserved unique nucleosynthetic fingerprints in the 0.01 to 0.1 permil range, which require challenging high precision measurements to be resolved. Hence, mixing processes in the protoplanetary disk led to homogenisation of extreme compositions, but did not fully erase them. Well established are enrichments in neutron-rich isotopes (e.g., 48Ca, 50Ti and 52Cr) compared to the Earth in samples from the outer region of our solar system (i.e. carbonaceous chondrites). These isotopes point towards supernova material that is enriched in the outer solar system. Correlated variations in Zr, Mo, Ru and Pd isotopes are well explained by the heterogeneous distribution of s-process material [1,2]. Such s-process variations are now also identified for heavier nuclides of Nd and W [3,4] and these variations are even smaller (few parts per million) than those of lighter isotopes e.g., of Zr and Mo. Overall, nucleosynthetic variations at bulk rock scale in heavier elements (Hf, W, Os, Pt, Hg) are very small or not resolvable. This also applies for p-process isotopes. For example, new high precision data of the rare 190Pt isotope demonstrate homogeneity in the solar system [5]. The same is true for the short-lived p-process radionuclide 92Nb (half-life = 37 million years). New data indicate an initial 92Nb/93Nb ratio of 1.68 (±0.10) × 10-5 for our solar system [6]. However, very specific refractory inclusions in meteorites (Group II CAIs) display 92Nb heterogeneities, apparently correlated with variations in the p-process isotope 84Sr. This correlation hints at the presence of a p-process dust carrier in the early solar system. [1] M. Ek, et al., LPSC 49, 1973 (2018). [2] W. Akram, et al., Geochim. Cosmochim. Acta 165, 484 (2015). [3] C. Burkhardt, et al., Nature 537, 394 (2016). [4] L. Qin, et al., Astrophys. J. 674, 1234 (2008). [5] A. Hunt, et al., Geochim. Cosmochim. Acta 216, 82 (2017). [6] M. Haba, et al., LPSC 48, 1739 (2017).

Speaker: Maria Schönbächler (ETH Zurich)

Abstract ID_181_Schoenbaechler.pdf

170 The Abundance of 60Fe in the Early Solar System

The abundance of the extinct radionuclide 60Fe (2.62 Myr half-life) in the early Solar System is highly disputed in the literature. On one hand, bulk measurements of early Solar System materials indicate an initial abundance consistent with galactic background [1, 2]. On the other hand, in situ studies by secondary ion mass spectrometry (SIMS) report a variety of ratios, e.g., [3], including some as high as 60Fe/56Fe = 1 × 10−6, e.g., [4]. Such high ratios are incompatible with galactic background and would require the injection of fresh nucleosynthetic material prior to the birth of the Solar System. Here we present new resonance ionization mass spectrometry (RIMS) measurements of a Semarkona chondrule (DAP1), which has been previously analyzed in situ by SIMS [3]. Despite improved precision compared to SIMS, our new RIMS measurements show no enhancement in 60Ni that could be attributed to the in situ decay of 60Fe. Our new value for the Solar System initial 60Fe/56Fe ratio of (6.4 ± 11.9) × 10−8 (2σ) is consistent with the low value as measured by bulk techniques and as found in some SIMS analy- ses, and agrees well with the 60Fe expected in galactic background. Our new result also agrees with a reevaluation of the previous SIMS DAP1 measurements. Supernova injec- tion of freshly synthesized 60Fe into the solar nebula just prior to the condensation of the first solids is thus not required to explain our measurement. It is however in agreement with a recent model by [5], which shows that Wolf-Rayet stars could have con- tributed the other short-lived radionuclides to the solar nebula, especially 26Al, without significantly enhancing 60Fe. Prepared by LLNL under Contract DE-AC52-07NA27344. and supported by NASA through grants NNX15AF78G (AMD), NNX11AG78G (GRH), and NNX14AI19G (GRH). LLNL-ABS-748505 References [1] H. Tang & N. Dauphas, E&PSL 359 (2012) 248. [2] H. Tang & N. Dauphas, ApJ 802 (2015) 22. [3] M. Telus et al. GCA 22 (2018) 342. [4] R. Mishra et al., E&PSL 22 (2016) 71. [5] V. V. Dwarkadas et al., ApJ 851 (2017) 147.

Speaker: Reto Trappitsch (Lawrence Livermore National Laboratory)

Abstract 145_Trappitsch.pdf

Slides Trappitsch_NIC2018_public_version.pdf

171 Isotopic compositions of trace elements in presolar SiC: new constraints on stellar nucleosynthesis

The isotopic compositions of trace elements in presolar grains provide unique constraints on stellar nucleosynthesis. The CHicago Instrument for Laser Ionization (CHILI) [1] is a laser resonance ionization mass spectrometer with unprecedented sensitivity and control of isobaric interferences, and 1ne lateral resolution, built primarily for applications in cosmochemistry. CHILI has recently been upgraded to its full designed capability, with the addition of: (1) a motionless-blanking Ga+ gun capable of sputtering with a lateral resolution of a few tens of nm; and (2) a multibounce mirror system that allows photoionization laser beams to pass 14 times through the sputtered cloud of atoms, greatly increasing sensitivity. CHILI has already made signi1cant progress in improving our knowledge of galactic chemical evolution (GCE), asymptotic giant branch (AGB) stars and core-collapse supernovae, through in isotopic compositions of trace elements in presolar SiC grains, all done with laser ablation at a lateral resolution of 1 m and without the multibounce mirror system. Fe and Ni isotopes in mainstream SiC grains from AGB stars show the effects of both GCE and neutron capture [2]. Sr and Ba isotopes in presolar SiC grains of Type X show two different types of isotopic patterns, representing the variety of heavy element nucleosynthesis sites with Type II supernovae [3]. Fe and Ni isotopes in Type X SiC grains show that signi1cant neutron capture effects occur in Type II supernovae [4]. Sr, Mo, and Ba isotopes in presolar SiC grains of Types AB1 and AB2 show that they come from Type II supernovae and J-type carbon stars, respectively [5, 6]. Correlated Sr and Ba, along with Ni isotopes in mainstream presolar SiC grains suggest that low-mass AGB stars have 13C pockets that cover a larger fraction of the helium intershell than was previously recognized [7]. References [1] T. Stephan et al., Int. J. Mass Spectrom. 407 (2016) 1. [2] R. Trappitsch et al., Geochim. Cosmochim. Acta 221 (2018) 87. [3] T. Stephan et al., Geochim. Cosmochim. Acta 221 (2018) 109. [4] J. Kodol´anyi et al., Geochim. Cosmochim. Acta 221 (2018) 127. [5] N. Liu et al., ApJ 855 (2018) 144. [6] N. Liu et al., ApJL 844 (2017) L12. [7] N. Liu et al., Lunar Planet. Sci. 49 (2018) 2035.

Speaker: Andrew Davis (University of Chicago)

Abstract 199_Davis.pdf

172 Short-lived radionuclei as clocks for the prehistory of the Solar System

While we know that stars are born in groups (clusters) within stellar nurseries, i.e., (possibly giant) molecular clouds, perhaps surprisingly, we do not have any consensus on the type of stellar nursery and stellar cluster where our Sun was born. Radioactive nu- clei with half-lives between roughly 10 and 100 Myr were present in the early Solar Sys- tem, as indicated by high-precision meteoritic analysis. They provide accurate clocks to measure the timing of the events that predated the formation of the Sun’s stellar nursery. By comparing predictions from the evolution of their galactic abundances to the meteoritic data we can build up a time line for the nucleosynthetic events that pre-dated the birth of the Sun (Figure 1), and investigate the lifetime of the stellar nursery where the Sun was born. However, many hurdles are still present between us and a clear picture of the Sun prehistory. These difficulties take the form of uncertainties in nuclear physics properties, stellar production, and Galactic evolution. We will present the current knowledge and discuss what is required to make the picture in focus.

Speaker: Maria Lugaro (Konkoly Observatory, Hungary)

Abstract 025_Lugaro.pdf

Slides NIC2018_Lugaro.pdf

11:00 Coffee break

Stellar contribution: massive stars and CCSNe

Convener: Hendrik Schatz (Michigan State University)

173 the evolution of massive stars: what we know and what we would like to know

I will review the key properties of the evolution of massive stars from the pre main sequence up to the core bounce plus the follow up of the shock wave and the associated explosive nucleosynthesis. I will discuss in particular which are the weakest points in the predictive power of the present computations as a function of the mass, metallicity and initial rotation velocity.

Speaker: Alessandro Chieffi (IAPS)

Abstract ID_014_CHIEFFI.pdf

Slides Chieffi_NIC2018_public_version.pptx

174 Learning from Nucleosynthesis from Multi-dimensional simulations of Core-Collapse Supernovae

For more that two decades, we have understood that the development of a successful core-collapse supernova is inextricably linked to neutrino heating and three dimensional fluid flows, with large scale hydrodynamic instabilities allowing successful explosions that spherical symmetry would prevent. Unfortunately, our understanding of the nucleosynthesis that occurs in these supernovae, and therefore the impact of supernovae on galactic chemical evolution, has generally ignored much that we have learned about the central engine of these supernovae over the past two decades. Now, with two and three dimensional simulations of core-collapse supernovae run to sufficient duration, we are learning how the multi-dimensional, neutrino-driven character of the explosions directly impacts the nucleosynthesis and other observables of core-collapse supernovae. I will present results for the nucleosynthesis calculated from simulations of a range of supernovae with our CHIMERA code, highlighting the ways that these results differ from the parameterized models that form the backbone of our understanding of supernova nucleosynthesis.

Speaker: William Hix (Oak Ridge National Laboratory)

Abstract ID_190_Hix.pdf

175 CANCELLED - Multi-d core collapse supernovae and nucleosynthesis

The explosion of massive stars as core-collapse supernovae represents one of the outstanding problems in modern astrophysics. Core-collapse supernovae figure prominently in the chemical evolution of galaxies as the dominant producers of elements between oxygen and the iron group, and they play an important role in the production of elements heavier than Fe. They represent a key ingredient in understanding the history of chemical enrichment of the Universe. We present in this work a detailed analysis of nucleosynthesis calculations of a 15 Msun neutrino-driven supernova explosions in 3D (explosions, approximative neutrino treatment, progenitors are presented by Wongwathanarat et al. 2017). Nucleosynthesis calculations are performed in a post-process using tracer particles method (TONiC code, Travaglio et al. 2011). The nucleosynthesis network used is based on 1500 isotopes, and for the first time about 500.000 tracer particles cover the star up to the explosive C-burning shell. We also discuss a the consequences for using different nuclear reaction networks (Basel 2009 as well as JINA 2012). The nuclear processes included are electron captures, neutron captures, alpha captures and photodisintegrations. A detailed comparison of the nucleosynthesis calculation between 3D and 1D models (where also the 1D model includes neutrino-driven explosion) will be presented providing interesting information on 1. overproduction of neutron-rich material 2. elemental and isotopic abundances information of elements like Mn, Cr, Sc, Cu & Zn to better understand the observations in metal-poor stars in our Galaxy as well as in external objects 3. radiogenic material 4. potential source of p-process nuclei.

Speaker: Claudia Travaglio (INAF - OATO)

Abstract 130_Travaglio.pdf

176 Bringing back core-collapse supernova explosions as r-process site

Canonical core-collapse supernova explosions, driven by the neutrino-heating mechanism, are presently ruled out as nucleosynthesis site for the production of heavy elements. Detailed numerical studies, with accurate neutrino transport and a sophisticated treatment of weak processes included, have shown that the ejected material does not yield sufficient neutron excess [1] for the production of elements with atomic numbers greater than 32 < Z < 50 [2], known as light neutron-capture elements. Here, we will review this caveat in the light of observations of metal-poor star (metalicity as stellar age tracer), dwarf galaxies and deep sea sediments. Based on new insights, we revisit the possibility that a few rare supernova explosion events can account for a strong r-process, i.e. the production of elements up to mass numbers of A ≃ 195 (third r-process peak). Therefore, it has been shown recently that the appearance of exotic phases of hot and dense matter, associated with a 1st-order phase transition from ordinary nuclear matter to the quark-gluon plasma at the supernova interior, triggers the onset of energetic supernova explosions of massive stars with zero-age main sequence masses of 40–50 M⊙ [3]. Moreover, these events yield a strong r process, which we will present and discuss here for the first time. Keywords: core-collapse supernovae - equation of state - nucleosynthesis References [1] G. Mart inez-Pinedo, T. Fischer, A. Lohs, and L. Huther, “Charged-Current Weak Interac- tion Processes in Hot and Dense Matter and its Impact on the Spectra of Neutrinos Emitted from Protoneutron Star Cooling,” Physical Review Letters, 109, 251104, 2012. [2] G. Mart ́ınez-Pinedo, T. Fischer, and L. Huther, “Supernova neutrinos and nucleosynthesis,” Journal of Physics G Nuclear Physics, 41, 044008, 2014. [3] T. Fischer, N.-U. F. Bastian, M.-R. Wu, S. Typel, T. Kla ̈hn, and D. B. Blaschke, “High- density phase transition paves the way for supernova explosions of massive blue-supergiant stars,” ArXiv e-prints, astro-ph.HE/1712.08788.

Speaker: Tobias Fischer (University of Wroclaw)

Abstract 156_FischerTobias.pdf

Slides fischer_nicxv.pdf

177 Nucleosynthesis in Core-Collapse Supernovae

Core-collapse supernovae (CCSNe) are one of the most important nucleosynthesis sites and they hold a key role in the evolution of galaxies. In the explosion, CCSNe eject freshly synthesized iron-group nuclei from explosive burning alongside of intermediate mass elements (from hydrostatic and explosive burning) and carbon and oxygen from the pre-explosion evolution. In the neutrino-driven wind, nuclei beyond the iron group can be synthesized under neutron-rich conditions (weak r-process) and proton-rich conditions (nu p-process). The signature of CCSN nucleosynthesis can be observed in the atmospheres of the oldest stars. Here, we will compare the nucleosynthesis from different progenitor models and different methods to trigger explosions in spherical symmetry. We will discuss the detailed synthesis pathways and the possible effects on the yields from the details of the progenitor and/or explosion properties.

Speaker: Carla Frohlich (NC State University)

Abstract 192_Frohlich.pdf

13:15 Lunch

Nuclear data and astrophysics

Convener: Gianluca Imbriani (Federico II University & INFN)

178 Mass measurements of short-lived nuclides in CSRe and its impact on some issues in nuclear astrophysics

Recent commissioning of the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou enabled us to conduct high-precision mass measurements at the Institute of Modern Physics in Lanzhou (IMP). In the past few years, mass measurements were performed using the CSRe-based isochronous mass spectrometry employing the fragmentation of the energetic beams of 36 Ar, 58 Ni, 78 Kr, 86 Kr, and 112Sn projectiles. Masses of short-lived nuclides of on both sides of the stability valley were measured[1–10]. Relative mass precision of down to 106 ∼ 107 is routinely achieved and some issues in nuclear structure and nuclear astrophysics have been addressed. In this talk, the experimental details are presented and the progress and some typical results are briefly introduced. The impacts of mass values on the reaction paths in rp- and ν p-process of nucleosynthesis in the stellar environments are discussed. References [1] X. L. Tu et al., Phys. Rev. Lett. 106 (2011) 112501 [2] X. L. Tu et al., Nucl. Instrum. Meth. A 654 (2011) 213 [3] Y. H. Zhang et al., Phys. Rev. Lett. 109 (2012) 102501 [4] X. L. Yan et al., Astrophys. Jour. Lett. 766 (2013) L8 [5] P. Shuai et al., Phys. Lett. B 735 (2014) 327 [6] X. Xu et al., Chin. Phys. C 39 (2015) 104001 [7] X. Xu et al., Phys. Rev. Lett. 117 (2016) 182503 [8] P. Zhang et al., Phys. Lett. B 767 (2017) 20 [9] Q. Zeng et al., Phys. Rev. C 96 (2017) 031303(R) [10] Y. M. Xing et al., Phys. Lett. B 781 (2018) 358

Speaker: Yu Hu Zhang (Institute of Modern Physics, CAS)

Abstract Zhang.pdf

Slides Zhang_NIC2018_public_version.pptx

179 Beta-delayed neutron emitters in the r‐process

Beta-delayed neutron (beta-n)-emitters play an important, two-fold role in the stellar nucleosynthesis of heavy elements in the "rapid neutron-capture process" (r-process). On one hand they lead to a detour of the material $\beta$-decaying back to stability. On the other hand, the released neutrons increase the neutron-to-seed ratio, and are re-captured during the freeze-out phase and thus influence the final solar $r$-abundance curve. For this reason the neutron branching ratio of very neutron-rich isotopes is a crucial input parameter in astrophysical simulations. A large fraction of the isotopes for r-process nucleosynthesis are not yet experimentally accessible and are located in the "Terra Incognita". With the next generation of fragmentation and ISOL facilities presently being built or already in operation, one of the main motivation of all projects is the investigation of very neutron-rich isotopes at and beyond the border of presently known nuclei. However, reaching more neutron-rich isotopes means also that multiple neutron-emission becomes the dominant decay mechanism. Since 2016 the BRIKEN project (“Beta-delayed neutron measurements at RIKEN for nuclear structure, astrophysics, and applications”) focusses on the most exotic betan-emitters which can presently be produced. The setup combines the most efficient neutron detection array in the world with a state-of-the-art implantation detector and two clover detectors. Several experiments were carried out in 2017 and covered 231 betan-emitter between 64Cr up to 151Cs. For many of these isotopes, betan-emission branching ratios have been measured for the first time, e.g. the doubly-magic N=50 isotope 78Ni, as well as about 50 new half-lives. More experiments for A>150 and A<60 will be carried out in the upcoming 2-3 years, making this experimental campaign one of the largest systematic investigation of two important nuclear physics input parameters for modelling the r-process nucleosynthesis. The expected results from the BRIKEN campaigns will excel results from the previous six decades and will help to improve the theoretical understanding of this complex decay mechanism tremendously, especially the competition between neutron emission and de-excitation via gamma-decay and emission of several neutrons. Almost all of the previously measured betan-emitters will be remeasured, and approximately 150 new betan emitters will be added to the list of 298 know betan-emitters. Also the number of measured multi-neutron emitters will be largely expanded. The inclusion of these new results in astrophysical network calculations will help to reduce the uncertainty in the calculated r-process abundances from this nuclear physics quantity.

Speaker: Iris Dillmann (TRIUMF)

Abstract ID_112_Dillmann.pdf

180 Experimental charged-particle (a,n) reaction studies relevant for the weak r-process

Core-collapse Supernovae explosions are likely to produce at least some of the elements heavier than iron found in nature. Although the conditions are not adequate to produce the heaviest elements, those explosions powered by neutron-rich neutrino-driven winds can contribute to the galactic abundance of elements from iron all the way to silver and beyond. Charged-particle reactions in the wind, mainly (alpha,n) and (alpha,2n) play an important role to create heavier mass nuclei. In order to validate these explosions as viable scenarios to produce heavy nuclei, it is critical to reliably predict the charged-particle reaction rates that control the production of elements. (alpha,n) and (alpha,2n) reaction rates used in nucleosynthesis calculations are calculated with statistical Hauser-Feshbach (HF) models as experimental information on (alpha,n) and (\alpha,2n) reaction rates is limited to a few stable isotopes in the region of interest and, even in those few cases, the data do not cover the energy range of astrophysical interest. However, the theoretical reaction rates often vary by an order of magnitude (when employing different nuclear physics input) and their large uncertainties directly results in unacceptable uncertainty in the final elemental abundances calculated within the astrophysical environment. In order to address these uncertainties, we have developed the neutron detector HABANERO (Heavy ion Accelerated Beam induced (Alpha,Neutron) Emission Ratio Observer) and started a program to constrain (alpha,n) and (alpha,2n) reaction rates of astrophysical interest. Preliminary results of the first experiment using HabaNERO, a measurement of the 75Ga(alpha,n)78As and 75Ga(alpha,2n)77As cross sections will be presented along with plans for future measurements.

Speaker: Fernando Montes (National Superconducting Cyclotron Laboratory)

Abstract 184_MontesFernando.pdf

181 Precise nuclear binding energies for the r process and core collapse

The r-process abundances depend sensitively on nuclear masses, i.e. binding energies. We have recently measured masses of several rare-earth nuclei with the JYFLTRAP Penning trap in Jyvaskyla and studied their impact on the r-process calculations. The rare-earth abundance peak at approx 165 forms during the later stages of the r-process and reflects both the astrophysical conditions as well as properties of nuclei in the region. The observed weaker neutron pairing toward the midshell at N=104 results in a smoother abundance pattern and in a better agreement with the observed solar r-process abundances. In addition to the main r process, we have determined masses of several nuclei close to 78Ni relevant for the core collapse phase of supernovae. Prior to collapse the nuclei are in nuclear statistical equilibrium (NSE), and the abundances are governed mainly by nuclear binding energies. On the other hand, electron captures on nuclei play a key role in the collapse. They drive matter toward more neutron-rich nuclei, cool the core via neutrino emission and reduce the amount of electrons thus affecting the electron degeneracy pressure resisting the gravitational collapse. In this contribution, I will give an overview of these recent mass measurements at JYFLTRAP and discuss their astrophysical motivation and impact. References M.R. Mumpower {et al.}, Progr. Part. Nucl. Phys. {\bf 86} (2016) 86. M.R. Mumpower {et al.}, Phys. Rev. C {\bf 85} (2012) 045801. M. Vilen {et al.}, arXiv:1801.08940v3 [nucl-ex] C. Sullivan {et al.}, Astrophys. J. {\bf 816} (2015) 44.

Speaker: Anu Kankainen (University of Jyväskylä)

Abstract 109_KankainenAnu.pdf

182 The beta-Oslo method: experimentally constrained (n,g reaction rates relevant to the r-process)

All elements found in our Universe, except for the very lightest ones, have been created during stars' lives and/or deaths. Burbidge, Burbidge, Fowler and Hoyle pointed out the slow neutron-capture and the rapid neutron-capture process to be the main contributors for producing elements from iron to uranium. On August 17, 2017, the LIGO and Virgo gravitational-wave detectors measured, for the first time, a direct signal from two colliding neutron stars. Follow-up measurements with telescopes sensitive to electromagnetic radiation confirmed that the r-process had indeed taken place in the collision (Ref.~\cite{Pian2017}). Hence, a long-standing question in nuclear astrophysics was solved; at least one astrophysical r-process site is now identified. However, the uncertain nuclear-physics input remains a huge obstacle in modeling the r-process yields in large-scale nucleosynthesis network calculations. The r-process inevitably involves highly neutron-rich nuclei, where there is a severe lack of relevant nuclear data such as masses, beta-decay rates and neutron-capture cross sections. Well away from the valley of stability, different theoretical predictions for neutron-capture rates may vary with several orders of magnitude. In this talk, a recently developed method to address this issue is presented: the beta-Oslo method provides data on the nuclear level density and average gamma-decay strength of moderately neutron-rich nuclei. These quantities are crucial input for calculations of neutron-capture rates, which in turn play a key role in a "cold" r-process scenario. The beta-Oslo method presents a first step towards constraining neutron-capture rates of importance to the r-process. References E.~M.~Burbidge \textit{et al.}, Rev. Mod. Phys. \textbf{29}, 547 (1957). B.~P.~Abbott \textit{et al.}, Phys. Rev. Lett. \textbf{119}, 161101 (2017). E. Pian \textit{et al.}, \textit{Nature} \textbf{551}, 67 (2017). M. Arnould, S. Goriely, and K. Takahashi, Phys. Rep. {\bf 450}, 97 (2007). A.~Spyrou \textit{et al.}, Phys. Rev. Lett. \textbf{113}, 232502 (2014). S.~N.~Liddick \textit{et al.}, Phys. Rev. Lett. \textbf{116}, 242502 (2016).

Speaker: Ann-Cecilie Larsen (University of Oslo)

Abstract 52_Larsen.pdf

Slides Larsen_Nuclei_in_the_Cosmos_XV_2018.pdf

183 Assessment of Stellar Nucleosynthesis Abundances using ENDF/B-VIII.0 and TENDL-2015 Evaluated Nuclear Data Libraries Content

Evaluated Nuclear Data File (ENDF) libraries contain complete collections of reaction cross sections, angular distributions, fission yields and decay data. These data collections have been used worldwide in nuclear industry and national security applications. It represents a great interest to explore the recently-released ENDF/B-VIII.0 library for nuclear astrophysics purposes and compare findings with the predictions of Talys Evaluated Nuclear Data Library (TENDL-2015) and Karlsruhe Astrophysical Database of Nucleosynthesis in Stars (KADoNiS). The Maxwellian-averaged cross sections (MACS) and astrophysical reaction rates were calculated using the ENDF/B-VIII.0 and TENDL-2015 evaluated data sets. The calculated cross sections were combined with the solar system abundances and fitted using the classical model of stellar nucleosynthesis. Astrophysical rapid- and slow-neutron capture, r- and s-processes, respectively, abundances are extracted from the present data and compared with available values. Further analysis of MACS reveals the potential astrophysical data deficiencies and strong needs for new measurements. The current results demonstrate large nuclear astrophysics potential of evaluated libraries and mutually beneficial relations between nuclear industry and research efforts.

Speaker: Boris Pritychenko (Brookhaven National Laboratory)

16:45 Coffee break

184 Poster prize ceremony

185 Special lecture - Explosive nucleosynthesis: what we learned and what we still do not understand

Speaker: Friedrich Thielemann (University of Basel)

186 Bus transfer to conference banquet

Conference banquet

Friday, 29 June

Stellar contribution: NS mergers

Convener: Friedrich Thielemann (University of Basel)

187 Gravitational-wave and multi-messenger astronomy

Ground-breaking discoveries happened during the first observing runs of the Advanced gravitational-wave detectors, LIGO and Virgo. On September 14 2015 the gravitational waves from the coalescence of a binary system of black holes marked the beginning of a new exploration of the Universe through gravitational waves [1]. This detection was followed by other detections of binary black-hole systems [2, 3, 4, 5]. Another epochal discovery happened on August 17, 2017 with the detection of the first gravitational waves from the inspiral and merger of a binary neutron-star system [6] and its electromagnetic signatures in all the bands from the high-energy to the radio [7]. The talk will give an overview of the astrophysical implications of the first gravitational-wave detections, which span from relativistic and nuclear astrophysics to fundamental physics and cosmology. I will describe the gravitational-wave and multi-messenger observations and the major results about our knowledge of the physics governing neutron stars, black holes, and the most energetic transients in the sky. Challenges and perspectives for the next years will be discussed. References [1] Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2016a, Physical Review Letters, 116,061102 [2] Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2016b, Physical Review Letters, 116,241103 [3] Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2017a, Physical Review Letters, 118,221101 [4] Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2017b, Physical Review Letters, 119,141101 [5] Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2017c, ApJL, 851, L35 [6] Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2017d, Physical Review Letters, 119,161101 [7] Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2017e, ApJL, 848, L12

Speaker: Marica Branchesi (Gran Sasso Science Institute)

Abstract ID_210_Branchesi.pdf

188 Measuring neutron star properties from thermonuclear bursts

Thermonuclear (type-I) X-ray bursts arise from unstable ignition of accreted fuel on the surface of neutron stars in close binary systems. Many nuclear reactions contribute to the burning that follows ignition (e.g. Galloway & Keek, 2017), and the rates of several reactions help to shape the burst light curve. It has long been a goal of observers to deduce information about these reactions (and the properties of the host objects) from the observational data available. In this presentation I will review recent progress reconciling numerical models with observations to meet this goal. Large samples of observational data, such as the Multi-INstrument Burst ARchive (MINBAR1) provide access to high quality, uniformly analysed observational data. Specific examples from this sample have been selected to serve as model test cases (Galloway et al., 2017). In parallel, a large sample of model predictions over a wide range of source conditions has been released (Lampe et al., 2016). Software tools are under development to comprehensively match observations to simulations, and hence determine the source parameters. Numerical models are also being applied to more ambitious targets, including entire transient outbursts (e.g. Johnston et al., 2018). These efforts are beginning to produce robust constraints on neutron star properties including accreted fuel composition, as well as neutron star mass and radius, that take into account many of the astrophysical uncertainties normally affecting such measurements. I will discuss future plans and prospects including the connection to nuclear experimental physics.

Speaker: Duncan Galloway (Monash University)

Abstract ID_091_Galloway.pdf

189 Nuclear Processes in the Crusts of Accreting Neutron Stars

Accreting neutron stars have crusts that differ in composition from regular neutron stars. The composition determines the thermal properties of the crust and thus observables during the accretion phase, such as X-ray bursts and superbursts in the shallow crust, as well as quiescent X-ray emission that probes the physics in the deeper regions of the crust. In addition accreted neutron stars have compositional boundaries where electron capture parent and daughter nuclei can coexist leading to a nuclear Urca process that further affect the thermal evolution. I will discuss results from recent calculations that determine for the first time the detailed composition of the outer crust, and the upper regions of the inner crust, and its implications for interpreting observables. It turns out that the shell structure of exotic neutron rich nuclei, as well as the interplay of X-ray burst physics and crust physics are of particular importance. I will also discuss recent experimental results from experiments at the National Superconducting Cyclotron Laboratory that determine location and strength of the most important Urca cooling nuclei through beta decay studies. I will conclude with an outlook for future work in theory as well as experiments at advanced rare isotope facilities such as FRIB.

Speaker: Hendrik Schatz (Michigan State University)

Abstract ID_113_Schatz.pdf

190 Predicting Neutron Capture Cross Sections from Nuclear Masses: implications for r-process Nucleosynthesis

A growing body of work has shown that individual neutron capture cross sections play an important role in the final isotopic abundances from a wide range of possible astrophysical scenarios, including wind ejecta from neutron star mergers. Unfortunately, the isotopes which seem to show the greatest impact are far from stability and not within experimental reach for direct measurements in the coming years. While indirect techniques are actively being developed to improve the state of the art, there is still a heavy reliance on Hauser Feshbach reaction theories, whose predictions quickly diverge by more than a factor of ten off stability. Motivated by this, we have recently discovered a previously unrecognized correlation between the neutron capture cross-section and the two-neutron separation energy. This offers several exciting possibilities. First, by parameterizing this simple correlation, we have been able to provide a new set of cross section predictions that can be used for nucleosynthesis studies. Second, because two-neutron separation energies can be measured with achievable rare beam intensities, the quality and quantity of S_2n data is far more reaching than what is available for neutron capture, allowing experimentally based extrapolations. Finally, this may offer hints into where traditional reaction theories have missed underlying physics that is needed to more accurately model the capture reaction process. We will present the discovered correlations as well as results from initial studies of the impact the deduced cross sections would have on r-process scenarios.

Speaker: Aaron Couture (Los Alamos National Laboratory)

Abstract ID_003_Couture.pdf

Slides Couture_NIC2018_public_version.pdf

191 The 59Cu(p,a) cross section and the heavy element nucleosynthesis in core collapse supernovae

A long standing problem in stellar evolution concerns the production mechanism for proton-rich heavy elements. These p-nuclei are thought to be produced in supernova explosions via photodisintegration of heavy elements. However, current stellar models fail to reproduce the observed abundances of lighter p-nuclei such as 92Mo and 96Ru [1]. An alternative possibility for production of the light p-nuclei may be the nu-p-process that is thought to occur in core collapse supernovae [2]. A recent study found that the efficiency of heavy element production depends on the strength of the 59Cu(p,a) reaction that may hinder the process by recycling material back to 56Ni, creating a closed NiCu cycle [3]. Therefore, the 59Cu(p,a)56Ni reaction cross-section is important in order to calculate the efficiency of the nu-p-process in producing the heavy elements. In addition, this reaction is also of importance for explaining the light curve of X-ray bursts, and affects the composition of burst ashes on the surface of the neutron star significantly [4]. Currently, there is no direct measurement of the 59Cu(p,a)56Ni reaction cross section. We present the preliminary results of a first such measurement. The experiment was performed at the HIE-ISOLDE facility at CERN in inverse kinematics by impinging the 59Cu beam on CH2 target. The reaction products, the alpha-particles and the 56Ni recoils, were detected in coincidence using a set of three annular silicon strip detectors. The measurement was made possible by using a purpose-built detection system provided by the University of Edinburgh and by taking advantage of the high intensity radioactive 59Cu beam available at HIE-ISOLDE. The upgrade to HIE-ISOLDE was needed to be able to perform this measurement at the beam energies that correspond to the temperatures of the stellar environment. The reaction has been studied at five different beam energies between 3.6 MeV/u and 5.0 MeV/u. I will present the scientific motivation, the experimental setup and running, and the first data. [1] M. Arnould and S. Goriely, Phys. Rep. 384, 1, (2003). [2] Frohlich et al., Phys. Rev. Lett. 96, 142502, (2006). [3] A. Arcones et al., Astrophys. Jour. 7500:18 (9pp), (2012). [4] R. H. Cyburt et al., Astrophys. Jour. 830:55 (20pp), (2016).

Speaker: Ruchi Garg (University of Edinburgh)

Abstract 139_GargRuchi.pdf

192 Impact of electron-captures on nuclei near N=50 on core-collapse supernovae

Sensitivity studies of the late stages of stellar core collapse with respect to electron-capture rates indicate the importance of a region of nuclei near the N=50 shell closure, just above doubly magic 78Ni. In the present work, it has been demonstrated that uncertainties in key characteristics of the evolution, such as the lepton fraction, electron fraction, entropy, stellar density, and in-fall velocity are about 50% due to uncertainties in the electron-capture rates on nuclei in this region, although thousands of nuclei are included in the simulations. The present electron-capture rate estimates used for the nuclei in this region of interest are primarily based on a simple approximation, and it is shown that the estimated rates are likely overestimated by an order of magnitude or more. More accurate microscopic theoretical models are required to obtain Gamow-Teller strength distributions, upon which electron-capture rates are based. The development of these models and the benchmarking of such calculations rely on data from charge-exchange experiments at intermediate energies. An experimental campaign to study Gamow-Teller strength distributions in nuclei at and near N=50, including 86Kr and 88Sr, with the (t,3He) reaction at NSCL is underway and preliminary results, and their effects on future astrophysical work, will be presented.

Speaker: Rachel Titus (NSCL/MSU)

Abstract 97_TitusRachel.pdf

Slides Ttitus_NIC2018_public_version.pdf

193 Fission properties relevant for GW170817

The recent observation of gravitational waves and electromagnetic counterpart to GW170817 [1] has provided fresh impetus to understand the formation of the heaviest elements on the periodic table. The merging of two neutron stars offers a potentially robust site for the neutron-rich nucleosynthesis of these elements in the rapid neutron capture process (r-process). However, many challenging problems remain in both the astrophysical modeling of merger events and the nuclear physics inputs. Among the nuclear physics needs for the r-process, fission properties may be particularly important. The dynamical ejecta of mergers is expected to be so neutron-rich that the resulting r-process produces nuclei above the predicted N=184 shell closure and terminates via fission. We focus our discourse on recent nuclear model developments in the description of fission apart of the Fission In r-process Elements (FIRE) collaboration. We discuss new calculations of neutron-induced and beta-delayed fission properties using FRDM2012. We present new microscopic fission yields predicted from FRLDM. We report on the relevance of these calculations to nucleosynthetic yields, the impact on reheating of the ejecta in addition to the influence on kilonova observations. [1] B. P. Abbott et al. PRL 119 161101 (2017).

Speaker: Matthew Mumpower (Los Alamos National Laboratory)

Abstract 129_MumpowerMatthew.pdf

Slides Mumpower_NIC2018_public_version.pdf

11:00 Coffee break

Stellar contribution: NS mergers Pt. 2

Convener: Thomas Rauscher (University of Basel & University of Hertfordshire)

194 R-process in Binary Neutron Star Mergers

Neutron star mergers had long been suspected to produce gravitational wave ”chirps”, gamma ray bursts and produce r-process elements. While overall convincing, all these conjectures were based on indirect arguments and none was proven directly. This changed on August 17, 2017: a gravitational wave signal from a merging neutron star binary was detected, closely followed by a short burst of gamma-rays and week-long transients across the electromagnetic spectrum coming from the radioactive decay of freshly synthesised r-process elements. In this talk I will give an overview over these recent events with a particular focus on the production of heavy elements.

Speaker: Stefan Rosswog (The Oskar Klein Centre, Stockholm University)

Abstract ID_211_Rosswog.pdf

195 Weak r-process in the blue-kilonova of double neutron-star mergers

The r-process nucleosynthesis has been considered to occur in explosive astronomical phenomena relevant to neutron stars, e.g. core-collapse supernovae and mergers of compact-object (neutron stars/black holes) binaries. However, detailed quantitative properties in astrophysical models for the r-process are not completely understood yet. In this talk, I will show recent results of r-process nucleosynthesis in neutron star mergers, based on our collaboration. As mass ejection through neutron star mergers has several phases with different nucleosynthesis composition, I will focus on nucleosynthesis yields on neutrino-driven ejecta in the post-merger phase, based on the hydrodynamical models by Fujibayashi et al. (2018), ApJ (in press, arXiv:1711.02093). The neutrino irradiated ejecta in the later phase is expected to be less neutron-rich and produce lighter and medium mass r-process nuclei. I will our results basically agree with the recent observation for the early blue component of kilonova associated with GW170817.

Speaker: Nobuya Nishimura (YITP, Kyoto University)

Abstract 197-Nishimura.pdf

Slides Nishimura_NIC2018_public_version.pdf

196 Modeling of the electromagnetic counterpart of compact binary merger: ejecta, neutrinos and nucleosynthesis

Compact binary mergers (CBMs) are cosmic laboratory for fundamental physics. All four fundamental interactions play a key role in setting the properties of the observables associated with these powerful stellar collisions. Thus, they need to be taken into account to provide reliable multimessenger predictions. In this talk, I will focus on the role of neutrinos and weak interaction in setting the properties and the composition of the ejecta. The impact on the features of the electromagnetic counterparts from CBMs will be investigated through a multicomponent, anisotropic kilonova model. The application of this model to the electromagnetic counterpart of GW170817 allows to derive key information on the amount and composition of the ejecta coming from this first detected binary NS merger. Finally, I will show how the application of this model to GW170817, in association with information derived from the analysis of the GW signal, and from one of the largest set of binary NS simulations in Numerical relativity, sets constraints on the nature of the remnant and on neutron star equation of state in a genuine multimessenger framework.

Speaker: Albino Perego (Milano Bicocca University & INFN)

Abstract 64_PeregoAlbino.pdf

Slides Perego_NIC2018_public_version.pdf

197 Conclusion

Speaker: Roland Diehl (MPE Garching)

13:00 Lunch

198 Bus to L'Aquila and Rome airports