# Strangeness in Nuclei and in Neutron Stars

Europe/Rome
N. 131, building C (Dipartimento di Fisica, Universita di Pisa)

### N. 131, building C

#### Dipartimento di Fisica, Universita di Pisa

Largo Bruno Pontecorvo, 3, Pisa (Italy)
Description
The “Strangeness in Nuclei and in Neutron Stars” workshop has the aim to set up an arena where young and experimented theoreticians and experimentalists, working in strangeness nuclear physics and astrophysics (neutron star studies), will discuss the most recent achievements and future perspectives of collaboration. The recent results in experimental strangeness physics, such as the kaonic atoms studies, hypernuclei and kaonic nuclear clusters research and kaon/hypernuclei-nucleon scattering, will be critically analyzed in the view of their possible relevance in astrophysics, more specifically in the equation of state of neutron stars, especially after the discovery of 2 solar masses stars. Is there any role strangeness plays in the Universe? This workshops plans to discuss the guiding lines towards finding answers to this fascinating question.

Topics
•  Kaonic atoms and kaonic nuclei
•  Hypernuclei
•  Kaon-nucleon and hyperon-nucleon interactions
•  Hyperonic three-body interactions
•  Hypernuclear matter
•  Hyperons and strange quark matter in neutron stars

Invited speakers

M. Cargnelli (Vienna), R. Del Grande (Frascati), A. Gal (Jerusalem),
D. Gazda (Trento),  R. Lea (Trieste), D. Logoteta (Pisa),  M. Merafina (Roma),
G. Pagliara (Ferrara),  F. Pederiva (Trento),  K. Piscicchia (Frascati),
A. Scordo (Frascati),  J. Zmeskal (Vienna).

Participants
• Alessandro Drago
• Alessandro Scordo
• Alessio Sodini
• Antonio Pasqua
• Avraham Gal
• Catalina Oana Curceanu
• Daniel Gazda
• Davide Decataldo
• Diana Laura Sirghi
• Domenico Logoteta
• Francesco Pederiva
• Giuseppe Pagliara
• Ignazio Bombaci
• Ivica Friscic
• Johann Zmeskal
• Kristian Piscicchia
• Marco Merafina
• Mathieu Renzo
• Michael Cargnelli
• raffaele de troia
• Raffaele Del Grande
• Ramona Lea
• Raquel Alvarez-Rodriguez
• sofia sarperi
• Wednesday, May 20
• 1
Light (anti)(hyper)nuclei production in Pb-Pb collisions measured with ALICE at the LHC
Thanks to its excellent particle identification capability, the ALICE detector allows for the identification of deuterons, $\rm ^{3}{He}$ and $\rm ^{4}{He}$ and their corresponding antinuclei. This is achieved via the measurement of their specific energy loss in the Time Projection Chamber and of their velocity by the Time-Of-Flight detector. Moreover, thanks to the Inner Tracking System ability to separate primary from secondary vertices, it is possible to identify (anti)hypertritons ($\rm ^{3}_{\Lambda}{H}$) exploiting their mesonic weak decay ($\rm ^{3}_{\Lambda}{H}$ $\rightarrow$ $^{3}\rm{He}$ + $\pi^-$) and to search for a hypothetical bound state of a $\Lambda$ with a neutron decaying into a deuteron and a pion. Results on the production of light nuclei and anti-nuclei in Pb--Pb and lighter collision systems (pp and p--Pb) will be presented. Hypernuclei production rates in Pb--Pb will also be shown, together with a measurement of the hypertriton lifetime and upper limits estimated on the production of lighter exotica candidates. The experimental results will be compared with the predictions of both thermal (statistical) and baryon coalescence models.
Speaker: Ramona Lea (TS)
• 2
X-rays of light kaonic atoms: SIDDHARTA and future
The X-ray measurements of kaonic atoms are important for understanding the low-energy QCD in the strangeness sector. The SIDDHARTA experiment studied the X-ray transitions of 4 light kaonic atoms (H, D, 3He and 4He) using the DAFNE electron-positron collider at LNF (Italy). The currently most precise values of the shift and width of the kaonic hydrogen 1s state were determined, which are now being used as fundamental information for the low-energy K-p interaction in theoretical studies. The yields of kaonic hydrogen K-series transitions and of the kaonic He3 and He4 L-series were measured, the upper limit of the X-ray yields of kaonic deuterium was determined, important for future K-d experiments. The shifts and widths of the kaonic 3He and 4He 2p states were analyzed, settling open points in this issue. In the contribution, the experimental approach and the results of SIDDHARTA will be presented, along with plans for new experiments on kaonic deuterium.
Speaker: Michael Cargnelli (Austrian Academy of Sciences - Stefan Meyer Institute)
• 1:00 PM
lunch
• 3
Y* resonances investigation in low-energy kaon-nuclei hadronic interactions
The AMADEUS experiment deals with the investigation of the low-energy kaon-nuclei hadronic interaction at the DA$\Phi$NE collider at LNF-INFN, which is fundamental to solve longstanding questions in the non-perturbative strangeness QCD sector. We analysed the 2004/2005 KLOE data, exploiting $K^-$ absorptions in $H$, ${}^4He$, ${}^{9}Be$ and ${}^{12}C$, to extract for the first time the module of the non-resonant transition amplitude, below threshold, in the I=1, $\Lambda \pi^-$ channel. A similar analysis is presently ongoing for the $\Sigma^+ \pi^-$ and $\Sigma^0 \pi^0$ (purely I=0) channels in order to study the shape of the controversial $\Lambda(1405)$ state.
Speaker: Mr Kristian Piscicchia (LNF)
• 4
Progress in Strangeness Nuclear Physics
In this talk I will discuss the progress made both experimentally and theoretically towards understanding the physics of hypernuclei, that is nuclear systems that include one or more strange baryons known as hyperons, mostly the Lambda(1116) lightest one, and which live sufficiently long to be explored in dedicated accelerator experiments. Some topical issues will be highlighted: light neutron-rich hypernuclei, the hyperon puzzle' in neutron stars, and the possible existence of a doubly-strange dibaryon known as Jaffe's H dibaryon. Time-permitting, I will also talk on antikaon-nuclear interactions and the search for antikaon-nuclear quasibound states, including the issue of antikaon condensation'.
Speaker: Prof. Avraham Gal (The Hebrew University, Jerusalem, Israel)
• 4:00 PM
coffee break
• 5
Equation of state of lambda-neutron matter from Quantum Monte Carlo calculations
I will review the recent progress we have reached in the ongoing study of strange matter using phenomenological potentials and Quantum Monte Carlo calculations. In particular I will focus on the discussion of the possibility of effectively constraining the interaction (in particular in the three-body sector) making use of the available experimental results. Some of our recent calculations, for instance, show that the hyperon-nucleon-nucleon interaction in the nucleon isospin triplet channel is very weakly constrained by the lambda separation energy in light and symmetric hypernuclei, pointing out the need of increasing the availability of experimental data for medium-mass asymmetric hypernuclei.
Speaker: Francesco Pederiva (TIFP)
• 6
The hyperonic three-body forces in hadronic matter
We calculate a two-meson exchange three-baryon potential between two nucleons and one hyperon (NNY). Our NNY potential is built in order to be consistent with the two-body nucleon-hyperon (NY) Julich 2004 (Ju04) potential of the Julich group. In particular, we focus on the NNΛ and NNΣ− forces since the Λ and Σ− are the first hyperons expected to appear in microscopic calculations of neutron star matter. We finally discuss several calculations of hyperonic matter, based on the Brueckner–Hartree–Fock approach, including the effect of the hyperonic three-body forces. These results suggest that at high densities the total contribution of the NNY force is repulsive making the resulting equation of state (EoS) stiffer, as required from neutron star mass observations.
Speaker: Dr Domenico Logoteta (INFN section of Pisa)
• Thursday, May 21
• 7
Combustion of hadronic stars into quark stars: the turbulent and the diffusive regimes
The conversion of a hadronic star into a quark star occurs within two different regimes. The first regime, characterized by turbulent combustion, occurs on very short time scales (of the order of ms) and it is decoupled from the neutrino cooling. In the second regime, turbulence is not active anymore, and the conversion proceeds, on a much longer time scale (of the order of tens of seconds), via diffusion and production of strange quarks. At the same time, neutrino cooling is also active. The interplay between the slow conversion of the outer part of the star and the cooling of the newly forming quark star leads to a plateau in the neutrino luminosity which, if observed, would possibly represent a unique signature for the existence of quark matter compact stars.
Speaker: Giuseppe Pagliara (FE)
• 8
Strangeness production using stopped antiprotons
The study of baryon-baryon interactions as a basic tool for the investigation of the strong interaction can be extended to the hyperon sector, where much less data exist, especially only few data are available on strangeness S = −2 systems. Stopped antiprotons are very efficient for the production of S = −2 systems via double strangeness and charge exchange reactions, which results in the production of anti-K* which will interact with another nucleon to form a Xi baryon. These studies will result in detailed information of S = −2 baryonic and possible di-baryonic states. A possible experimental setup will be discussed as well as the future possibility for a source of intense, low-momentum antiprotons at FAIR.
Speaker: Mr Johann Zmeskal (SMI)
• 9
Gravity and termodynamics in globular clusters: new theoretical and numerical developments
Stellar dynamics - N-body simulations
Speaker: Prof. Marco Merafina (University of Rome La Sapienza)
• 11:00 AM
coffee break
• 10
Observational properties of Type Ia Supernovae according to the Double Degenerate model
Type Ia Supernovae (SNe) are explosive events of relevant importance in Physics and Astrophysics but many aspects about their origin are nowadays unclear. In particular there is a great debate about the nature of the progenitor binary system and its evolution up to the explosion. The aim of this work was to verify if a selected model of SNe Ia progenitors is able to provide observational counterparts whose existence can be observationally tested. We refer to the Double Degenerate system in which two White Dwarfs (WDs) merge because of Gravitational Waves emission from the system. It has been assumed that the less massive WD is completely dissolved into an optically thick disk which accretes matter into the remaining WD of the system [1]. Since the amount of matter that can be accreted on the star depends on its structural features, it is possible to determine the properties of the accreting WD and that of the disk all along their time evolution from first principles ([2],[3]) and to numerically follow the full evolution of the merged system from the merging to the explosion [4]. Since the evolutionary time scales are known and also known is the rate of type Ia SNe occurring in the Galaxy, we could easily derive the expected number of systems existing in the Galaxy and statistically estimate their spatial distribution. We reproduced the spectral distribution of each expected pre-exploding system once the position, the dust extinction in the Galaxy and the WD and disk properties were known. From the obtained spectral distribution, the fluxes in various relevant observational bands have been obtained (namely those of the Sloan Digital Sky Survey and those of the GALEX telescopes). The apparent magnitudes have been obtained to make a comparison with the matched GALEX and SDSS data catalogs. [1] Lorén-Aguilar, P., Isern, J., Garcìa-Berro, E. 2010, MNRAS, 406, 2749 [2] Piersanti, L., Gagliardi, S., Iben, I.Jr., Tornambé, A. 2003, ApJ, 583, 885 [3] Piersanti, L., Gagliardi, S., Iben, I.Jr., Tornambé, A. 2003, ApJ, 598, 1229 [4] Tornambé, A. & Piersanti, L. 2013, MNRAS, 431, 1812-1822
Speaker: Dr Raffaele Del Grande (LNF-INFN)
• 11
K- four nucleon absorption process studies through the Λt channel
The study of the low-energy negatively charged kaons interactions with the nuclear matter will be presented. In particular, the interactions of the kaons produced at the DAΦNE collider with the He nuclei present in the drift chamber gas and with the C nuclei contained in the drift chamber wall of the KLOE detector, generating the Λt final state are studied. This channel gave us the possibility to investigate the K- four nucleon absorption (4NA), a process which is poorly studied by other experimental and theoretical works. Dedicated MC simulations of the 4NA of the K- in He and C are performed and the experimentally extracted invariant mass, momentum and angular distributions spectra were fitted, in order to obtain for the first time the absolute value of the BR and the σ (100 MeV/c) for the 4NA process leading to the Λt pair in the final state.
Speaker: Alessandro Scordo (LNF)
• 12
Ab Initio Calculations of Light Hypernuclei
In this contribution I will report on our recent ab initio study of nuclear systems with strangeness. We formulated hypernuclear no-core shell model methodology and performed large-scale calculations of light s-shell as well as p-shell Lambda hypernuclei. In our calculations we employed realistic nucleon-nucleon, three-nucleon and hyperon-nucleon interactions. In particular we focused on baryon-baryon interactions derived within chiral perturbation theory.
Speaker: Daniel Gazda (ECT*)