Diffraction 2014

10 Sept 2014, 17:00 → 15 Sept 2014, 23:00 Europe/Lisbon

Primošten (Croatia)

Alessandro Papa (Universita` della Calabria & INFN-Cosenza), Kornelija Passek-Kumericki (Rudjer Boskovic Institute, Zagreb)

Diffraction 2014 is the eigth biennial Workshop dedicated to theoretical and experimental progress in diffractive processes at high energies.

Organized and sponsored by:
Istituto Nazionale di Fisica Nucleare (Italy)
Rudjer Boskovic Institute, Zagreb  (Croatia)
Università della Calabria (Italy)
University of Zagreb (Croatia)
HadronPhysics3 within Seventh Framework Programme (FP7) of EU
DESY Hamburg
CERN. Sito ufficiale

Wednesday, 10 September

17:00 → 19:30 Registration

18:30 → 19:30 Welcome Drink

19:30 → 21:00 Dinner

Thursday, 11 September

09:00 → 09:20 Opening address

09:20 → 10:50 Diffraction in DIS (I)

Convener: D.A. Ross

09:20 Inclusive DIS and PDFs

Recent results on deep-inelastic scattering at HERA are presented. These include new H1 and ZEUS measurements of the proton longitudinal structure function FL and new combined measurements of the DIS inclusive cross sections based on the full HERA inclusive data samples published up to now. The new combined H1 and ZEUS neutral and charged current inclusive cross sections are used as the sole input to NLO and NNLO QCD analyses to determine new sets of parton distributions, HERAPDF2.0, with small experimental uncertainties and an estimate of model and parametrisation uncertainties.

Speaker: Enrico Tassi (CS)

Slides diffraction2014-etassi.pdf

09:50 Updates of PDFs in MSTW framework

I present an update of the PDFs obtaining using the same overall framework as MSTW. In particular I concentrate on the effect of new data sets, particularly from the LHC, but compare the changes in the PDFs resulting from this source to changes due to some differences in theoretical procedure.

Speaker: Dr Lucian Harland-Lang (IPPP Durham)

Slides lhldiff2014.pdf

10:20 HERAFitter - open source QCD Fit framework and its related studies

HERAFitter project provides a framework for Quantum Chromodynamics(QCD) analyses related to the proton structure. Based on the factorisation concept, HERAFitter allows determination of parton distribution functions(PDFs) from the various hard scattering measurements. Diffractive PDFs as well as alternative approaches to DGLAP can be used to analyse DIS data at low-x with HERAFitter. Here we also report a set of PDFs determined using HERA data and preserving correlations between uncertainties.

Speaker: Ringaile Placakyte (DESY)

Slides placakyte_diffraction14.pdf

10:50 → 11:20 Coffee break

11:20 → 12:35 Diffraction in DIS (II)

Convener: M. Ruspa

11:20 Heavy flavour production at HERA

Measurements of heavy-quark production at HERA constrain the structure of the proton, and have provided valuable indications of perturbative QCD.Several measurements of heavy quark production in deep inelastic scattering and photoproductions regimes, using different decay modes, are presented, both new individual measurements from the H1 and ZEUS collaborations, as well as combined data. QCD fits to the data lead to measurements of the charm and beauty masses and also provide precise predictions for e.g. W and Z production at the LHC.

Speaker: Mr Andrii Gizhko (DESY Hamburg)

Slides gizhkohfdiff14.pdf

11:45 Recent results on Charmonium production at HERA

Exclusive charm vector meson production has been studied in the high statistics HERA-2 data. H1 has measured the elastic and proton-dissociative photoproduction cross sections of J/psi mesons as function of W_{gamma p} and t. The W_{gamma p} and t dependencies are parametrised using phenomenological fits, and results are compared to other measurements. ZEUS has measured the cross section ratio of exclusive DIS production of psi(2S) to psi(1S) as function of Q^2, W_{gamma p} and t.

Speaker: Dr Nelli Gogitidze (LPI, Moscow / DESY, Hamburg)

Slides DIFF2014_Gogitidze.pdf

12:10 QCD and Hadronic Final States

The production of inclusive jets as well as of dijet and trijet topologies is investigated with the high statistics HERA II data. The H1 and ZEUS experiments have determined the corresponding cross sections with improved experimental precision, compared to previous measurements. For both experiments, a hadronic energy scale uncertainty as small as 1% is reached. The value of the strong coupling constant alpha_s(M_Z) is extracted and its running is probed. Measurements with the ZEUS data of the photoproduction of isolated photons, both inclusive and in association with a jet, are reported, including studies of kinematic variables sensitive to the event dynamics. The measurements are compared to higher order theoretical calculations. Using topologies involving high track multiplicities and an associated jet, the H1 data are used to search for the production and decay of QCD instantons. A recent measurement of charged particle spectra in the H1 ep DIS data is also presented.

Speaker: Mr Jan Olsson (DESY)

Slides DIFF2014_Olsson.pdf

12:35 → 15:30 Lunch and leisure time

15:30 → 17:10 Diffraction in DIS (III)

Convener: M. Ruspa

15:30 Photoproduction of isolated photons at HERA

The photoproduction of isolated photons, both inclusive and together with a jet, has been measured with the ZEUS detector at HERA using an integrated luminosity of 374pb−1. Differential cross sections are presented in the isolated-photon transverse-energy and pseudorapidity ranges 6

Speaker: Oleg Kuprash (DESY)

Slides Diffraction2014_Kuprash.pdf

15:55 Measurement of Exclusive Dijet Production in Diffractive DIS with the ZEUS Detector at HERA

The exclusive production of dijets in diffractive deep inelastic lepton-proton scattering has been measured with the ZEUS detector at HERA with an integrated luminosity of 372 inverse picobarn. Jets have been reconstructed in the photon-Pomeron rest frame using the exclusive kt algorithm. The shape of the differential cross-section as a function of the angle between the plane spanned by the incoming and scattered lepton momenta and the plane spanned by the virtual photon and jets momenta is presented. The shape is determined by jet production mechanism and provides information about Pomeron structure.

Speaker: Mr Grzegorz Gach (AGH University)

Slides Gach_Dijets.pdf

16:20 Recent HERA results with very forward neutrons and photons

Two new analyses exploring different kinematic regimes are presented, based on H1 data collected in the years 2006-2007: inclusive neutron and photon production in DIS and exclusive rho0 production associated with forward neutrons in photoproduction. The former reaction is analysed in terms of the Feynman scaling hypothesis and compared to various Monte Carlo models, none of which is able to describe the data in all respects. The latter process is interpreted in terms of a double peripheral process involving pion and Pomeron exchanges. Within the OPE approach the elastic cross section of photon-pion scattering at =22 GeV is extracted.

Speaker: Dr Sergey Levonian (DESY)

Slides Diff2014_levonian.pdf

16:45 Diffraction and Low x Physics at a Large Hadron electron Collider

The Large Hadron Electron Collider is a proposed upgrade to the LHC in which the existing proton or heavy ion beams collide with a newly constructed electron beam of nominal energy 60 GeV, simultaneously with ongoing pp or AA collisions. As well as the overall status of the project, prospects for diffractive physics studies in particular and low x physics more generally will be discussed in this presentation.

Speaker: Paul Newman (Birmingham)

Slides Diff14-Newman.pdf

17:10 → 17:40 Coffee break

17:40 → 19:25 Diffraction in DIS (IV)

Convener: D.A. Ross

17:40 Access to Generalized Parton Distributions at COMPASS

A brief experimentalist's introduction to Generalized Parton Distributions (GPDs) is given. Recent COMPASS results are shown on exclusive production of neutral rho-mesons, and their interpretation in terms of a phenomenological model as indication for chiral-odd, transverse GPDs is discussed. It is briefly outlined how to access GPDs at COMPASS and projections are shown for future [2016/17] COMPASS measurements of exclusive reactions, in particular Deeply Virtual Compton Scattering and hard exclusive vector meson production.

Speaker: Dr Wolf-Dieter Nowak (DESY/Freiburg University)

Slides Nowak_DIFFRACTION2014.pdf

18:05 Some news about GPDs and hard exclusive processes

We report on some new theoretical results for the representation of generalized parton distributions (GPDs), the understanding of next-to-leading order corrections to hard exclusive processes, the calculation of higher twist corrections to deeply virtual Compton scattering, and we present the first global GPD fit to H1 and ZEUS data.

Speaker: Dr Dieter Mueller (Ruhr-University Bochum)

Slides 02-Mueller.pdf

18:25 Breakdown of diffractive factorization

The Pomeron structure measured in diffractive DIS is a higher twist and cannot be applied to diffractive hadronic collisions. Interaction with the spectators breaks factorization of soft and hard interactions and results in a leading twist effect.

Speaker: Prof. Boris Kopeliovich (UTFSM)

Slides kopeliovich.pdf

18:45 Impact factor for quark-antiquark-gluon jet production in DDIS

We present the calculation of the impact factor for the photon to quark, antiquark and gluon transition within Balitsky's high energy OPE. We also rederive the impact factor for photon to quark and antiquark transition within the same framework. These results provide the necessary building blocks for further phenomenological studies of inclusive diffractive DIS as well as for two and three jets diffractive production which go beyond approximations discussed in the litterature.

Speaker: Mr Renaud Boussarie (LPT Orsay)

Slides BoussarieDiffraction2014.pdf

19:05 New approach to QCD Factorization

Factorization is the fundamental concept in order to apply QCD calculations to description of hadronic reactions. According to Fac- torization, theoretical study of any hadronic process includes both parton scattering and parton distributions. The partonic sub-processes are calcu- lated with the use of regular methods of perturbative QCD. In contrast, the parton distributions are introduced purely phenomenologically, without any theoretical grounds. There are two popular kinds of Factorization in the literature: Collinear and kT - factorizations. They were introduced indepen- dently of each other. We show that both the kT - and collinear factorization can be obtained by consecutive reductions of some more general (Basic) fac- torization. Each of these reductions is an approximation valid under certain assumptions. First, the transitions from Basic to kT - factorization assumes that the mo- menta of the partons connecting the perturbative and non-perturbative blobs are mostly transverse. This assumption fairly agrees both with the DGLAP and BFKL. Second, if the unintegrated parton distributions in kT -factorization have a maximum(s) in kT , then kT - factorization can be reduced to collinear factor- ization. The sharper the maximum is, the better is accuracy of the transition. This assumption can be checked with analysis of available experimental data. Integration over momenta of the connecting partons in the Basic factorization for amplitudes of the forward Compton scattering o hadrons must yield a nite result. This obvious requirement allowed us to deduce theoretical con- straints on the parton distributions both in kT - and Collinear factorizations.

Speaker: Prof. Boris Ermolaev (Ioffe Physico-Technical Institute)

Slides 05-Ermolaev.pdf

19:25 → 21:00 Dinner

Friday, 12 September

08:30 → 10:30 Forward physics in Hadron-Hadron Collisions (I)

Convener: A. Levy

08:30 Totem results

The TOTEM experiment measured the elastic, inelastic and total pp cross-section at sqrt(s)= 7 TeV and 8 TeV. The elastic scattering was measured in a large range of |t| allowing the determination of the pp cross-section, the discrimination among the elastic models and the study of the Coulomb-Nuclear interference |t|-region. The measurement of the charged particle dN/deta and the status of the analyses on soft single, double, and central diffractive interaction will be also reported.

Speaker: Dr Mirko Berretti (CERN)

Slides MirkoBerretti-diffraction2014.pdf

08:50 Diffraction and Forward Physics results from the ATLAS experiment

Recent diffraction and forward physics results from the ATLAS experiment are presented, based on data collected in the Run I, which include measurements of forward rapidity gaps, gap fraction and azimuthal decorrelation using jet veto and total proton-proton cross section.

Speaker: Dr Marek Tasevsky (Institute of Physics of ASCR, Prague)

Slides Tasevsky-Diffraction2014-results.pdf

09:10 CMS results on multijet correlations

We present recent CMS measurements on multijet correlations using forward and low-pT jets, focusing on searches for BFKL and saturation phenomena. In p-p collisions at sqrt(s)=7 TeV, azimuthal correlations in dijets separated in rapidity by up to 9.4 units were measured. The results are compared to BFKL- and DGLAP-based predictions. In p-p collisions at sqrt(s)=8 TeV, cross sections for jets with pT>21 GeV and |y|<4.7, and for minijets with pT>1 GeV are presented. The minijet results are sensitive to the bound imposed by the total inelastic cross section, and are compared to various models for taming the growth of the 2->2 cross section at low pT.

Speaker: Dr Grigory Safronov (ITEP)

Slides safronov_multijets_diff14_1.pdf

09:30 QCD measurements in the forward acceptance at the LHC

Due to its unique pseudorapidity coverage and the possibility of extending measurements to low transverse momenta, LHCb allows studies of different QCD processes in a kinematic range where models have large uncertainties. We present charged particle multiplicity measurements, different with respect to transverse momentum and pseudorapidity, as well as recent results on the energy flow and inelastic cross-section.

Speaker: Dr Murilo Rangel (UFRJ)

Slides RANGEL_QCD_LHCb

09:50 The CT-PPS project

The CMS-Totem Precision Proton Spectrometer project is presented. The status of ongoing developments is described, and future plans are discussed. Ada Solano, on behalf of the CMS and TOTEM Collaborations

Speaker: Ada Maria Solano (TO)

Slides 05-Solano.pdf

10:10 Forward Physics at the LHC with tagged protons

In this talk, we will describe briefly some of the physics topics that can be studied at the LHC using tagged protons, namely QCD and the structure of the pomeron in terms of quarks and gluons, as well as the search for extra-dimensions in the universe via anomalous couplings between photon, W and Z.

Speaker: Dr Christophe Royon (IRFU-SPP, CEA Saclay)

Slides croatia2014.pdf

10:30 → 11:00 Coffee break

11:00 → 12:40 Forward physics in Hadron-Hadron Collisions (II)

Convener: C. Mesropian

11:00 Double Pomeron Exchange: the early days (ISR and SPS)

The first observations of double pomeron exchange (DPE) reactions were in pp collisions at the CERN Intersection Storage Rings (ISR) in the early 1980’s, with C.M. energies up to 63 GeV. These were followed by many detailed studies at the SPS and at the Tevatron (fixed target), with lower C.M. energy but higher statistics and a variety of final state produced hadrons. I will give a mini-review of these experiments, which may not be familiar to the younger generation, but are still very relevant.

Speaker: Michael Albrow (Fermilab)

Slides 01-Albrow.pptx

11:20 STAR results on central exclusive production in pp collisions

Preliminary measurement of the Central Exclusive Production of the two oppositely charged pions produced in the process $pp\to pp \pi^+\pi^-$, obtained with the STAR detector at RHIC at \sqrt{s} = 200 GeV is presented. The Roman Pots were used to tag forward protons while pion pair tracks were reconstructed in the STAR Time Projection Chamber (TPC). Predictions of models based on Regge phenomenology are compared to the spectra of the kinematical variables corrected for detector acceptance and efficiency.

Speaker: Prof. Mariusz Przybycien (AGH University of Science and Technology)

Slides diffraction_2014.pdf

11:40 Central Exclusive $\pi^{+}\pi^{-}$ Production in $p \bar{p}$ Collisions at $\sqrt{s}= 0.9$ and 1.96 TeV at the Tevatron

We have measured exclusive $\pi^{+}\pi^{-}$ production in proton-antiproton collisions at $\sqrt{s}=$0.9 and 1.96 TeV in the Collider Detector at Fermilab. We selected events with exactly two oppositely charged particles in $|\eta|<1.3$, with no other particles detected in $|\eta|<5.9$. The central $\pi^{+}\pi^{-}$ was required to have rapidity $|y|<1$. By requiring no other charged particles, these events are dominated by double pomeron exchange, which constrains the quantum numbers of the central state. The data show resonance structures attributed to the $f_0$ and $f_2$ mesons. We place upper limits on exclusive $\chi_{c0}\rightarrow\pi^{+}\pi^{-}$ and $\chi_{c0}\rightarrow K^{+}K^{-}$.

Speaker: Ms Maria Zurek (FZ Juelich, University of Cologne)

Slides MariaZurekDiff2014.pdf

12:00 CMS results on exclusive and diffractive production

We report on the CMS measurements of exclusive and diffractive processes, including the latest CMS measurements of exclusive and diffractive production of dijets, dimuons and vector bosons in pomeron- and photon-induced collisions in p-p at 7 TeV. The data are compared to various theoretical predictions.

Speaker: Prof. Gilvan Alves (CBPF/MCT)

Slides Diff14_talk-v1.pdf

12:20 Exclusive J/Psi and Psi(2S) vector meson production

An updated measurement of exclusive J/psi and psi(2S) vector meson production is presented. The forward reach of the LHCb detector is sensitive to the gluon PDF down to x=5E-6. The data are compared to predictions at LO and NLO order and to model that include saturation effects, which may become important at such low x-values. Comparisons are also made to photoproduction results from HERA and fixed target experiments. A first result of exclusive di-charm production is also presented.

Speaker: Dr Murilo Rangel (UFRJ)

Slides 14_Diffraction_CEP.pdf

12:40 → 15:30 Lunch and leisure time

15:30 → 17:10 Diffraction in Hadron-Hadron Collisions (I)

Convener: B. Kopeliovich

15:30 Charge exchange reaction at high energies

Charge exchange reactions at high energies are examined. Such reactions can in principle be tagged in pp-collisions by their topology of asymmetric forward charges of Z_tot=0 and Z_tot=2. The low energy data of the reaction pp \rightarrow n \Delta^{++} are reviewed, and extrapolated to LHC and FCC energies. The charge exchange reaction induced by W^{+},W^{-}-exchange is presented. The prospects of identifying charge exchange reactions at the LHC and FCC colliders are discussed.

Speaker: Dr Rainer Schicker (Phys. Inst., University Heidelberg)

Slides diff2014_schicker.pdf

15:50 Lessons from LHC elastic & diffractive data

We discuss a model which gives a `global' description of the wide variety of high-energy elastic and diffractive data that are presently available, particularly from the LHC experiments. The model is based on only one pomeron pole, but includes multi-pomeron interactions. Significantly, the LHC measurements require that the model includes the transverse momentum dependence of the intermediate partons as a function of their rapidity, which results in a rapidity (or energy) dependence of the multi-pomeron vertices. We may call this the k_t(s) effect.

Speaker: Prof. Alan Martin (IPPP, Durham)

Slides LessonsLHC.pdf

16:10 pp Elastic Scattering at LHC Energies

Using a unified analytic representation for the elastic scattering amplitudes of pp scattering for all energies, the behavior of observables at the LHC energies in the range 2.76 - 14 TeV is discussed. Similary to the case of 7 TeV data, the proposed amplitudes give excellent description of the preliminary data at 8 TeV. We discuss the energy dependence of the observables, with predictions for the experiments at 2.76, 13 and 14 TeV and investigate asymptotic properties of pp collisions.

Speaker: Mr Anderson Kendi Kohara (Universidade Federal do Rio de Janeiro)

Slides 03-Kohara.pdf

16:30 Tension in the LHC Diffractive Data ?

I discuss the results for diffractive production at the LHC, and indicate that the discrepancies present in the results of the different collaborations is not unique. Examples of similar disagreement in other high energy data is presented and conclusions drawn. A survey is made of models attempting to describe high energy diffractive data.

Speaker: Errol (Asher) Gotsman (Tel Aviv University)

Slides primeg1.pdf

16:50 Asymptotic Scenarios for the Proton's Central Opacity: An Empirical Study

We present a model-independent analysis of the experimental data on the ratio X between the elastic and total cross-sections from pp and \barpp scattering in the c.m. energy interval 5GeV-8TeV. Using a novel empirical parametrization for that ratio as a function of the energy and based on theoretical and empirical arguments, we investigate three distinct asymptotic scenarios: either the black-disk (BD) limit or scenarios above and below that limit. Our analysis favors a scenario below the BD, with asymptotic ratio X=0.36 \pm 0.08. Assuming the saturation of the Pumplin bound, the predicted asymptotic ratio of the soft diffractive cross-section to the total cross-section reads 0.14 \pm 0.08.

Speaker: Mr Paulo V R G Silva (Universidade Estadual de Campinas)

Slides DIFF2014_PVRGSilva.pdf

17:10 → 17:40 Coffee break

17:40 → 19:20 Diffraction in Hadron-Hadron Collisions (II)

Convener: E. Levin

17:40 RENORM Predictions of Diffraction at LHC Confirmed

The RENORM model predictions of differential and integrated diffractive, total, and total-inelastic cross sections at the LHC are confirmed by recent measurements. The predictions of several other available models are discussed, highlighting their differences from RENORM, mainly arising from the way rapidity gap formation, low- and high-mass diffraction, unitarization, and hadronization are implemented.

Speaker: Prof. Konstantin Goulianos (The Rockefeller University)

Slides 01-Goulianos.pdf

18:00 The hadron structure and the description of the elastic scattering in a wide region of $t$ and $s$

The analysis of different sets of the PDFs is made in the framework of the model of t-dependence of the GPDs. On the basis of the new high energy general structure model, which takes into account the different moments of the GPDs of the hadron the quantitative descriptions of all existing experimental data from 9.8 GeV to 7 TeV, including the Coulomb range and large momentum transfers up to -t=15 GeV^2, is obtained with only 3 free fitting high energy parameters. The real part of the hadronic amplitude is determined only through complex s satisfying the dispersion relations. The possible contributions of the hard Pomeron and maximal Odderon was examined.

Speaker: Dr Oleg Selyugin (Joint Institute for Nuclear Research)

Slides 02-Selyugin.ppt

18:20 Impact picture for near-forward elastic scattering up to LHC energies

We will recall the main features of an accurate phenomenological model to describe successfully near-forward elastic scattering in a wide energy range, including ISR, SPS and Tevatron colliders. A large step in energy domain is accomplished with the LHC collider presently running, giving a unique opportunity to confront the new data with the predictions of our theoretical approach.

Speaker: Prof. Jacques Soffer (Temple University, Philadelphia, PA, USA)

Slides 03-Soffer.pdf

18:40 Multi-pion Meson Productions in Diffractive and Central Productions at COMPASS and at ALICE

Recent results on (pi pi pi)− from COMPASS from a study of the reaction pi- p -> pi+ pi- pi- + p at 190 GeV/c. A new state is found, at mass = 1420 GeV with JPC = 1++ and decaying to f0(980)pi− and f0(980) pi+pi−. This state has never been seen before and never been predicted by theorists or anticipated by experimentalists on meson spectroscopy. Because of its very small cross section, it is NOT likely to be a quarkonium but an exotic meson consisting of tetra-quarks (q¯q)0 + (q¯q)− or it could be a gluonic hybrid (q¯q)− + (a valence gluon), where q’s stand for the light-mass quarks, i.e. q = {u, d, s}. ALICE Collaboration are currently analyzing the (pi+pi−)0 and (pi+pi−pi+pi−)0 systems pro- duced in a central production via double-Pomeron or Pomeron-Reggeon exchanges from p+p at 7 TeV. Recent results from partial-wave analyses of the two- and four-pion systems are presented.

Speaker: Prof. Suh-Urk Chung (CERN/BNL/PNU(Pusan National University, Busan, Republic of Korea))

Slides mytalk3.pdf

19:00 Anomalous Photon-Gauge-Boson Coupling Contribution to the Exclusive Vector Boson Pair Production from Two Photon Exchange in pp Collision at 8 TeV

We study the W/Z pair production from two photon exchange in pp collisions at the LHC in order to evaluate the contributions of anomalous photon-gauge-boson couplings, predicted in many Standard Model (SM) extensions. We start by reproducing the total cross section for W+ W- production and we present the lepton invariant mass distribution corresponding to the SM signal with pT (e mu) > 30 GeV. Next, we consider the anomalous couplings by calculating the Z pair production process by considering a 1 TeV scale for new physic effects. We calculate the total cross section and we present the transverse momentum distribution for the fully leptonic final state with zero extra tracks.

Speaker: Dr José Sá Borges (Universidade do Estado do Rio de Janeiro)

Slides 05-SaBorges.pdf

19:20 → 21:00 Dinner

Saturday, 13 September

08:20 → 10:20 Spin Physics (I)

Convener: J. Soffer

08:20 Proton spin in leading order of the covariant approach

In the framework of the covariant quark-parton model we study the relativistic interplay between the quark spins and orbital angular momenta, which collectively contribute to the proton spin. The spin structure functions g1 and g2, corresponding to the many-quark state J =1/2 are shown to satisfy constraints and relations, which fit well the available experimental data including the data on proton spin content ΔΣ ≲ 1=3. The suggested Lorentz-invariant three-dimensional approach for calculation of the structure functions is compared with the approach based on the conventional collinear parton model. For details see Phys.Rev. D89, 014012 (2014).

Speaker: Dr Petr Zavada (Institute of Physics ASCR, Prague)

Slides zavada_diff14.pdf

08:45 Spin Physics Program in Jefferson Lab's Hall C

The nucleon spin structure has been studied at Jefferson Lab's Hall C in experiments RSS (E01-006) and SANE (E07-003), which measured double spin asymmetries using the U. of Virginia solid polarized target and CEBAF's 6 GeV polarized electrons. The proton longitudinal spin structure g1 and transverse structure g2 have been investigated at kinematics extending from the elastic point to DIS, for four-momenta squared ranging from 0.8 to 5 GeV^2. The neutron structures have been measured in the region of the nucleon resonances at 1.3 GeV^2 on a deuteron target. Results of both experiments will be highlighted. A brief survey of approved experiments for the 12 GeV program will also be presented.

Speaker: Dr Oscar A. Rondon (Institute for Nuclear and Particle Physics - Univ. of Virginia)

Slides Spin Program in Hall C

09:10 Jefferson Lab Spin Structure Measurements at Low Q2

The latest generation of electron scattering experiments at Jefferson Lab endeavor to completely describe the nucleon in terms of the fundamental de- grees of freedom of Quantum Chromodynamics. A critical component of this program is to understand how the spin of the nucleon arises from its sub- structure, and what role spin plays in the structure of more complex nuclear systems. The Jefferson Lab spin-dependent data allows tests of effective the- ories of QCD, provides constraints on bound state Q.E.D. calculations, and can provide unique tests of novel physics, such as searches for hidden color components of nuclear wavefunctions. We’ll discuss results from the Jefferson Lab spin structure program, and provide a perspective on upcoming spin-dependent experiments at the newly upgraded 12 GeV continuous electron beam accelerator facility.

Speaker: Prof. Karl Slifer (UNH)

Slides slifer_diffraction_2014.pdf

09:35 How large is the gluon polarization in the statistical parton distributions approach?

We review the theoretical foundations of the quantum statistical approach to parton distributions and we show that by using some recent experimental results from Deep Inelastic Scattering, we are able to improve the description of the data by means of a new determination of the parton distributions. We will see that a large gluon polarization emerges, giving a significant contribution the the proton spin.

Speaker: Prof. Jacques Soffer (Temple University, Philadelphia, PA, USA)

Slides 04-Soffer.pdf

09:55 The spin physics results from COMPASS

Latest COMPASS results on quark and gluon helicities are discussed, as well as results on transverse spin and transverse momentum effects in semi-inclusive deeply inelastic scattering of 160 GeV/c muons off proton and deuteron targets.

Speaker: Dr Oleg Kouznetsov (JINR)

Slides 05-Kouznetsov.pptx

10:20 → 10:40 Coffee break

10:40 → 13:00 Spin Physics (II)

Convener: J. Soffer

10:40 Spin physics results from STAR

In order to better understand the spin structure of the proton, the STAR detector detects the collision products of polarised protons. Our ability to collide protons at various center of mass energies and to reconstruct jets from -1 < \eta < 2 and pions and etas up to \eta of 4 allows for sensitivity to different probes, kinematics and different mixes of partonic subprocesses. I will present recent results of the STAR spin physics program, such as inclusive jet asymmetries indicating a non-zero gluon polarisation for x > 0.05, W asymmetries indicating a preference for sea quark polarisations, recent transverse spin asymmetries results, as well as discuss possible future developments.

Speaker: Nikola Poljak (University of Zagreb, STAR collaboration)

Slides Diffraction_Npoljak_v3.pdf

11:05 Spin physics results from PHENIX

The PHENIX spin physics program seeks to understand the spin structure of the proton through study of polarized proton collisions. We study asymmetries produced in collisions of both longitudinally and transversly polarized protons at a variety of center of mass energies. Recent results from the observation of neutral and charged meson, W boson, and heavy flavor final states will be presented.

Speaker: Paul Kline (Stony Brook University)

Slides 02-Kline.pdf

11:25 Towards a Pion Generalized Parton Distribution Model from Dyson Schwinger Equations

We compute the pion quark Generalized Parton Distribution and quark Double Distributions in a coupled Bethe Salpeter and Dyson Schwinger approach in terms of quarks flavors or isospin states. We use simple analytic expressions inspired by the numerical resolution of Bethe Salpeter and Dyson Schwinger equations. We explicitly check the support and polynomiality properties, and the behavior under charge conjugation or time invariance of our model. We obtain analytic expressions for the Double Distributions and Generalized Parton Distribution at vanishing pion momentum transfer at a low scale. Our model compare very well to experimental pion form factor or parton distribution function data.

Speaker: Dr Hervé Moutarde (Irfu, CEA-Saclay)

Slides 03-Moutarde.pdf

11:50 A Polarized Drell-Yan Experiment to Probe the Dynamics of the Nucleon Sea

In QCD, nucleon spin comes from the sum of the quark spin, gluon spin, and the quark and gluon orbital angular momentum, but how these different components contribute and the interplay among them is not yet understood. For instance, sea quark orbital contribution remains largely unexplored. Measurements of the Sivers function for the sea quarks will provide a probe of the sea quark orbital contribution. The upcoming E1039 experiment at Fermilab will measure the Sivers asymmetry of the sea quarks via the Drell-Yan process using a 120 GeV unpolarized proton beam directed a transversely polarized ammonium target. We report on the status and plans of the E1039 polarized Drell-Yan experiment.

Speaker: Dr David Kleinjan (Los Alamos National Laboratory)

Slides 2014_09_13_Diffraction.pdf

12:15 Comparing T-odd and T-even spin sum rules

The sum rules (SRs), in particular the ones related to momentum and angular momentum conservation, are discussed. The cases of distribution, fragmentation and fracture (diffractive distribution) functions are compared. The SRs for T-odd distribution functions include the phases borrowed from hard subprocesses. The possible SR validity for each flavour and justification of the existence of nodes of Sivers function are discussed. The stability of SRs against QCD evolution is analyzed. The interplay of SRs for inclusive and exclusive processe is considered. The relations to the equivalence principle for nucleon spin interaction with gravity and its generalization are discussed.

Speaker: Prof. Oleg Teryaev (JINR)

Slides 05-Teryaev.ppt

12:40 Results on Transverse Spin Asymmetries in Polarized Proton - Proton Elastic Scattering at sqrt(s) = 200 GeV

We present a preliminary result on a precision measurement of the transverse double spin asymmetries ANN and ASS in polarized proton-proton elastic scattering at sqrt(s) = 200 GeV in the small four momentum transfer squared (t) region 0.005 < -t < 0.035 (GeV/c)2, the Coulomb Nuclear Interference (CNI) region. This preliminary result is based on about 20 million elastic events acquired by the STAR experiment at RHIC during the run with dedicated optics of β*=20m. The preliminary values of ANN and ASS show that they are about equal, small but distinguishable from zero: ANN ≈ ASS = – 0.0051±0.0006(stat)±0.0010(sys). We shall also present the result on the single transverse spin asymmetry AN obtained from the same sample of events. The result on AN can be explained by the interference of electromagnetic spin-flip and hadronic non-flip amplitude.

Speaker: Dr Wlodek Guryn (For the STAR Collaboration)

Slides WlodekDiff2014V2.pdf

13:00 → 14:00 Lunch and leisure time

14:00 → 20:00 Excursion

20:00 → 21:00 Dinner

Sunday, 14 September

08:30 → 10:30 Progress in QCD (I)

Convener: D. Ivanov

08:30 On the BLM optimal renormalization scale setting for semihard processes

We apply the BLM scale setting procedure directly to the amplitudes (cross sections) of several semihard processes. It is shown that due to the presence of {$\beta_0$}-terms in the NLA results for the impact-factors the obtained optimized renormalization scale is not universal, it depends both on the energy and on the type of the process in question. We illustrate this general conclusion considering in details the following semihard processes: $p+p\to {\rm jet}+{\rm jet} +X$, the inclusive production of two forward high-$p_T$ jets separated by large interval in rapidity $\Delta y$ (Mueller-Navelet jets); the high-energy behaviour of the total cross section for highly virtual photons; the forward amplitude of production of two light vector mesons in collision of two virtual photons $\gamma^*\gamma^*\to V_1V_2$.

Speaker: Beatrice Murdaca (CS)

Slides 01-Murdaca.pdf

08:50 Test of BFKL dynamics at the LHC

After recalling the fits to the forward jet cross sections at HERA in order to test the BFKL dynamics, we will give our predictions concerning the Mueller Navelet and jet gap jet cross sections at the LHC, ad we will mention the jet veto measurements performed by the ATLAS collaboration. We will finish by proposing a new measurement of the jet gap jet events in DPE events.

Speaker: Dr Christophe Royon (IRFU-SPP, CEA Saclay)

Slides croatia2014_bfkl.pdf

09:10 Renormalization group analysis of reggeon field theory

We investigate the possibility whether reggeon field theory can serve as an effective description for high energy QCD at long distances. As a first step we study the fixed point structure of local reggeon field theory.

Speaker: Dr Joachim Bartels (University Hamburg)

Slides Bartels-Primosten-2014.pdf

09:30 Non-perturbative effects for the BFKL equation

Two models for the region of small transverse momenta in the BFKL equation are discussed. In the first of them the gluons are massive as a result of the Higgs mechanizm. For the second case the impact parameter space is compactified, which can serve as a model for the confinement based on the dual Meissner effect. Further, the non-Fredholm properties of the BFKL kernel at the collinear kinematics in the t-channel allow us to calculate its eigenvalues in a semi-classical approximation for N=4 SUSY in all orders of perturbation theory.

Speaker: Prof. Lev Lipatov (Petersburg Nuclear Physics Institute)

Slides Croat14.pdf

09:50 The Green Function for the Discrete BFKL Pomeron

We describe the solution to the BFKL equation with running coupling, leading to a set of discrete Regge poles, in terms of a universal green function and discuss the conditions under which this Green function can lead to amplitudes which match those of a DGLAP analysis in the leading logarithm approximation

Speaker: Prof. Douglas Ross (Southampton University)

Slides ross.pdf

10:10 Discontinuities of multi-Regge amplitudes in the next-to-leading order

Calculation of s-channel discontinuities of multi-Regge amplitudes in the next-to-leading logarithmic approximation in the BFKL approach is discussed. The discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is calculated explicitly in the planar N=4 SYM and compared with the result obtained using the two-loop 6-point remainder function derived as the expectation value of the Wilson loop.

Speaker: Prof. Victor Fadin (Institute of Nuclear Physics SB RAS)

Slides Fadin.pdf

10:30 → 11:00 Coffee break

11:00 → 12:40 Progress in QCD (II)

Convener: J. Bartels

11:00 The $\gamma^* \gamma^*$ total cross section in NLA BFKL.

We study the $\gamma^* \gamma^*$ total cross section in the NLA BFKL approach. We have extracted the NLO corrections to the photon impact factor from two recent papers of Balitsky and Chirilli and Chirilly and Kovchegov. Then use them to build several representations of the total cross section, equivalent within the NLA. We have combined these different representations with two among the most common methods for the optimization of a perturbative series, namely PMS and BLM, and compared their behavior with the energy with the only available experimental data, those from the LEP2 collider.

Speaker: Dr Dmitry Ivanov (Sobolev Institute of Mathematics)

Slides 01-Ivanov.pdf

11:20 Unified BFKL and DGLAP evolution in terms of theta

We present an evolution equation which simultaneously sums the leading BFKL and DGLAP logarithms for the integrated gluon distribution in terms of a single variable, namely the emission angle of the gluon. This form of evolution is appropriate for Monte Carlo simulations of events of high energy prton-proton interactions, particularly where small x events are sampled.

Speaker: Prof. Alan Martin (IPPP, Durham)

Slides Unified_BFKL_DIFF2014.pdf

11:40 QCD mechanisms of (semi)exclusive Drell-Yan processes

The (semi) exclusive pion-nucleon Drell-Yan processes with different non-perturbative QCD ingredients are considered. The classical one involves proton Generalized parton distribution (GPD) and pion distribution amplitude, while another one invloves proton and pion GPDs. For the first mechanism collinear factorization holds while for the second one the analytic continuation may be applied. The possible cancellations between different cuts are discusssed. The contributions of both mechanisms (and interference in the case of transitional GPD for the first mechanism) are clculated at Born level. The generalization to gluon GPDs case and central exclusive Higgs production is discussed,

Speaker: Prof. Oleg Teryaev (JINR)

Slides 03-Teryaev.ppt

12:00 Double parton effects for jets with large rapidity separation

We discuss production of four-jet final state $pp \to jjjjX$ in proton-proton collisions at the LHC through the mechanism of double-parton scattering (DPS) in the context of jets with large rapidity separation. The DPS contributions are calculated within the so-called factorized Ansatz and each step of DPS is calculated in the LO collinear approximation. The LO pQCD calculations are shown to give a reasonably good descritption of recent CMS and ATLAS data on inclusive jet production and therefore this formalism can be used to reliably estimate the DPS effects. Relative contribution of DPS is growing at large rapidity distance between jets. This is consistent with our experience from previous studies of double-parton scattering effects in the case of open and hidden charm production. The calculated differential cross sections as a function of rapidity distance between the most remote in rapidity jets are compared with recent results of LL and NLL BFKL calculations for Mueller-Navelet (MN) jet production at $\sqrt{s}$ = 7 TeV. The DPS contribution to the production of jets widely separated in rapidity is carefully studied for the present energy %\sqrt{s}$ = 7 TeV and also at the nominal LHC energy $\sqrt{s}$ = 14 TeV and in different ranges of jet transverse momenta. The differential cross section as a function of dijet transverse momenta as well as two-dimensional $(p_T(y_{min}),p_T(y_{max})$ -plane correlations for DPS mechanism are also presented. Some ideas how the DPS effects could be studied in the case of double dijet production are suggested. This research was published recently [1]. [1] R. Maciula and A. Szczurek, Phys. Rev. D90, 014022 (2014).

Speaker: Antoni Szczurek (Institute of Nuclear Physics, Krakow and Rzeszow University, Rzeszow)

Slides 04-Szczurek.pdf

12:20 On effects of multiple gluons in J/psi hadroproduction

Prompt J/psi hadroduction is considered beyond the leading twist two-gluon production mechanism. A contribution to the process is analysed in which the meson production is mediated by three-gluons, with two gluons coming from the target and one gluon from the projectile. Such contribution is enhanced at large energies due to large double gluon density at small x. This contribution is calculated within perturbative QCD, in the k_T factorisation approach and it is found to be significant correction to the leading twist cross-section at the energies of the Tevatron or the LHC. The results are given as differential pT-dependent cross-sections for J/psi polarisation components.

Speaker: Mariusz Sadzikowski (Jagiellonian University)

Slides diff_2014.pdf

12:40 → 15:30 Lunch and leisure time

15:30 → 16:50 Progress in QCD (III)

Convener: A. Szczurek

15:30 TMD pdfs and DY lepton pair production at LHC

We consider the transverse momentum dependent (TMD) quark densities of the proton which are very important ingredients for unpolarized Drell-Yan lepton pair production in proton-proton collisions at the LHC energies. We calculate the TMD sea quark density as a convolution of the Catani-Ciafaloni-Fiorani-Marchesini-evolved gluon distribution and the TMD gluon-to-quark splitting function. This splitting function contains all single logarithmic small-x corrections to the sea quark evolution for any order of perturbation theory. Based on the O(α) production amplitude q∗+q¯∗→Z/γ∗→l++l−, calculated by taking into account the effective q∗q¯∗Z/γ∗ vertex, we analyze the distributions on the dilepton invariant mass, transverse momentum and rapidity and specific angular correlations between the produced leptons as measured by the CMS, ATLAS and LHCb collaborations. We show that our predictions are sensitive to the TMD quark distributions of the proton.

Speaker: Nikolai Zotov (Moscow State University)

Slides 01-Zotov.pdf

15:50 Twist expansion of differential cross-sections of forward Drell-Yan process

In my talk I will present twist expansion of differential cross-sections of forward Drell-Yan (DY) process at high energies. The expansion of all invariant DY form-factors is performed assuming GBW saturation model, and the saturation scale plays the role of the hadronic scale of OPE. Results are given both for the differential cross-sections dependent on the Drell-Yan pair transverse momentum qT and for the inclusive cross-sections. It is shown that the Lam-Tung relation is satisfied at twist 2 and broken at twist 4. The results open the way for a forthcoming analysis of multiple scattering and higher twist effects in DY process at the LHC.

Speaker: Mr Tomasz Stebel (Jagiellonian University)

Slides primosten_Stebel.pdf

16:10 NLO Vertex for a Forward Jet plus a Rapidity Gap at High Energies

We present the calculation of the forward jet vertex associated to a rapidity gap (coupling of a hard pomeron to the jet) in the BFKL formalism at next-to-leading order(NLO). We handle the real emission contributions making use of the Lipatov's effective action. This result is important since it allows, together with the NLO non-forward gluon Green function, to perform NLO studies of jet production in diffractive events (Mueller-Tang dijets, as a well-known example).

Speaker: Mr José Daniel Madrigal Martínez (IPhT CEA Saclay)

Slides Diffraction2014-MuellerTang.pdf

16:30 The photon PDF of the proton

We show how the photon input parton distribution function (PDF) may be calculated with good accuracy, and used in an extended DGLAP global parton analysis in which the photon is treated as an additional point-like parton. The uncertainty of the input photon PDF is relatively small, since the major part of the distribution (which is produced by the coherent emission of the photon from a proton that remains intact) is well known. We present the expected photon PDFs, and compare the predictions with ZEUS data for isolated photon electroproduction at negative rapidities.

Speaker: Prof. Alan Martin (IPPP, Durham)

Slides photonPDF_DIFF2014.pdf

16:50 → 17:20 Coffee break

17:20 → 19:00 Saturation

Convener: L. Motyka

17:20 Why mean pt is interesting

We review recent ALICE data on mean pt in pp and in pPb collisions. First we show that multiplicity spectra exhibit geometrical scaling (GS) and then we study its consequences as far as mean pt is concerned. Next we discuss appropriate scaling variable for mean pt dependence on N_ch which is related to the interaction radius R. We use Color Glass Condensate results for R dependence on N_ch. Finally we show what are the limitations on the energy behavior of R at fixed multiplicity and propose a simple model in which R at large N_ch tends to a fixed value that does not depend on energy. Such behavior has testable phenomenological consequences that seem to be supported by the data.

Speaker: Prof. Michal Praszalowicz (Jagiellonian University)

Slides praszalowicz_meanpt.pdf

17:40 On parton number fluctuations at various stages of the rapidity evolution

Starting with the interpretation of parton evolution with rapidity as a branching-diffusion process, we describe the different kinds of fluctuations of the density of partons which affect the properties of QCD scattering amplitudes at moderately high energies. We then derive some of these properties as direct consequences of the stochastic picture. We get new results on the expression of the saturation scale of a large nucleus, and a modified geometric scaling valid at intermediate rapidities for dipole-dipole scattering.

Speaker: Dr Stéphane Munier (CPHT, Ecole Polytechnique, CNRS)

Slides munier_v1.pdf

18:00 Large impact parameter behaviour and CGC/saturation approach: the BFKL equation with massive gluon

I will discuss the solution to the BFKL equation with massive gluon.Such equation arises in the electro-weak theory with the zero Weinberg angle . However, for us, the gauge invariant theory with the Higgs mechanism for the creation of mass gives the instructive example of the theory in which has correct large impact parameter behaviour. The spectrum of this equation which coincide with the spectrum of massless BFKL equation will be discussed as well as the expected asymptotical behaviour of the scattering amplitude.

Speaker: Prof. Eugene Levin (Tel Aviv University/UTFSM)

Slides 03-Levin.pdf

18:20 Next-to-leading order corrections for scattering amplitudes in high-energy QCD

The rapidity (energy) evolution of hadronic observables in scattering of a diluted, perturbative projectile, on a dense gluonic target is described in QCD by the JIMWLK equation. This is a functional non-linear equation that is consistent with the QCD unitarity and reduces to the linear BFKL equation when the scattering probability is low. Recently, there was major progress in this field - the NLO JIMWLK Hamiltonian was calculated by means of a comparison of the general structure of the NLO Hamiltonian with the NLO evolution equations of quark dipole and Baryon. In my talk I will present the ideas which enabled us determining the NLO correction.

Speaker: Mr Yair Mulian (PhD student)

Slides JIMWLK_presentation_DIFFRACTION.pdf

18:40 Particle Production in Dilute-Dense Collisions and Rapidity Correlations

Multi-particle production with rapidity correlations in high-energy pA collisions can be studied through a generalization of the JIMWLK Hamiltonian applying to a generating functional describing the projectile. We also address the physical picture described by different viewpoints on the evolution equations governing these generating functionals.

Speaker: Mr José Daniel Madrigal Martínez (IPhT CEA Saclay)

Slides Diffraction2014-Production.pdf

20:00 → 22:30 Social dinner

Monday, 15 September

09:00 → 11:00 LHC and post-LHC

Convener: R. Orava

09:00 The AFP project in ATLAS

Status of the AFP (ATLAS Forward Proton) project is reported including technical aspects and physics motivation.

Speaker: Dr Marek Tasevsky (Institute of Physics of ASCR, Prague)

Slides Tasevsky-Diffraction2014-AFP.pdf

09:20 New results on Central Exclusive Production

Central exclusive production (CEP) processes in high-energy proton -(anti)proton collisions offer a very promising framework within which to study both novel aspects of QCD and new physics signals. We discuss charmonium CEP applying the Durham model for evaluation of the rates and proton momentum correlations at the Tevatron and LHC energies. We also present the results of a recent novel application of the 'hard exclusive' PT formalism to the CEP of dijets and dimeson CEP which, in particular, opens a way to probe the gluon component of the meson wave-functions.

Speaker: Prof. Valeri Khoze (IPPP, University of Durham)

Slides khozeDIF14__.ppt

09:40 Vector meson production in ultra-peripheral collisions at the LHC

By using a Regge-pole model for vector meson production (VMP), successfully describing the HERA data, we analyze the correlation between VMP cross sections in photon-induced reactions and those in ultra-peripheral collisions at the Large Hadron Collider (LHC). The important role of non-linear trajectories is emphasized. Predictions for future experiments on production of $J/\psi$ and other vector mesons are presented.

Speaker: Prof. Laszlo Jenkovszky (Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine)

Slides Diff_2014_Primosten.ppt

10:00 Probing Generalized Parton Distributions in Ultraperipheral Collisions

Ultraperipheral collisions in hadron colliders give new opportunites to investigate the hadron stucture through exclusive photoproduction processes. I will describe the possibility of measuring the Generalized Parton Distributions in the Timelike Compton Scattering process and in the production of heavy vector meson.

Speaker: Dr Jakub Wagner (National Centre for Nuclear Research)

Slides Wagner_diff2014.pdf

10:20 The existence and uniqueness of diffraction at the LHC

We discuss the mathematical ill-posedness of measuring diffractive cross sections at the LHC. As a solution, a Bayesian algorithmic framework is proposed to regularize the ill-posedness.

Speaker: Mikael Mieskolainen (Helsinki Institute of Physics, University of Helsinki)

Slides Primosten_Mieskolainen.pdf

10:40 Polarization Test For Higgs Spin and Parity

A polarization test for the formation of a resonance is developed and applied to determine the spin and the parity of the Higgs particle. The test is based on very general principle and is completely independent of dynamical assumptions. A set of observables are identified that distinguish between J^P =0^+, 0^-, 2^+, 2^- states.Furthermore, the same set of observables provide useful information on the magnitude of each helicity amplitude contributing to the gg->H->\gamma \gamma process.

Speaker: Prof. Firooz Arash (Tafresh University)

Slides Arash_Diffraction_2014.pdf

11:00 → 11:30 Coffee break

11:30 → 11:50 Diffraction in DIS (V)

Convener: W. Guryn

11:30 Diffractive dijet production in DIS and gamma-p

The QCD factorization theorem in diffraction is tested by comparing diffractive jet production data to QCD predictions based on fits to inclusive diffractive cross section data. H1 measured dijet production with a leading proton detected in the Very Forward Proton Spectrometer (VFPS), both in deep-inelastic scattering and in photoproduction. The DIS measurements are complemented by measurements of dijet production with an associated rapidity gap and in a data sample selected with a leading proton in the Forward Proton Spectrometer (FPS).

Speaker: Dr Richard Polifka (Charles University in Prague)

Slides PolifkaDiffDijets.pdf

11:50 → 12:50 Diffraction in Nuclear Physics (I)

Convener: W. Guryn

11:50 Exclusive photoproduction of J/psi and psi(2S) in pp and AA collisions

The amplitude for γp→J/ψp (γp→ψ′p) is calculated in a pQCD kT-factorization approach. The total cross section for this process is calculated for different unintegrated gluon distributions and compared with the HERA data and the data extracted recently by the LHCb collaboration. The amplitude for γp→J/ψp (γp→ψ′p) is used to predict the cross section for exclusive photoproduction of J/ψ (ψ′) meson in proton-proton and nucleus-nucleus collisions. In the pp case, compared to earlier calculations we include both Dirac and Pauli electromagnetic form factors. We also discuss the dependence of nuclear shadowing on the charmonium state.

Speaker: Dr Wolfgang Schaefer (Institute of Nuclear Physics PAN)

Slides 01-Schafer.pdf

12:10 Exclusive photoproduction of quarkonium at the LHC energies within the color dipole approach

In this contribution we present our recent results for the coherent photoproduction of vector mesons psi(1S), psi(2S) and Upsilon (1S) in the hadron-hadron and nucleus-nucleus collisions in the LHC energies. Predictions for the rapidity distributions are presented using the color dipole formalism and including saturation effects that are expected to be relevant at high energies. Comparison is done to the J/psi and Psi(2S) photoproduction data from LHCb Collaboration on proton-proton collisions at 7 TeV and data from ALICE collaboration on lead-lead reactions at 2.76 TeV. Predictions are performed for the Upsilon states in proton and nucleus target as well.

Speaker: Prof. M.Beatriz Gay Ducati (Universidade Federal do Rio Grande do Sul- UFRGS)

Slides Gay_Ducati.pdf

12:30 Diffractive cross sections in high energy heavy ion reactions with the dipole formalism

Recent developments in the Lund Dipole Cascade Model make it possible to study diffractive processes in high energy heavy ion collisions by this tools. In the dipole formalism of parton interactions fluctuations are naturally included and adding them to the pomeron ladder they substantially determine the diffractive excitation cross sections in such reactions. Our Monte Carlo event generator provides results for pA and \gamma-A diffractive cross reactions that are shown and discussed. A general observation is that their ratios compared to the total cross sections are relatively small but not negligible.

Speaker: Andras Ster (Wigner RCP, Budapst, Hungary)

Slides 03-Ster.pdf

12:50 → 15:30 Lunch and leisure time

15:30 → 16:45 Diffraction in Nuclear Physics (II)

Convener: W. Guryn

15:30 Soft and Hard probes of proton multiple scattering in p+Pb collisions with the ATLAS experiment at the LHC

Proton-Lead (p+Pb) collisions at the Large Hadron Collider provide a unique opportunity to study the dynamics of soft and hard scattering processes in nuclear targets, at the TeV scale. The ATLAS experiment has measured the inclusive charged particle pseudorapidity distribution, the production of Z bosons and and the inclusive jet production in p+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. These measurements are presented as a function of “centrality”, an experimental quantity that indirectly constrains the p+Pb collision geometry. The p+Pb collision centrality was characterized by the total transverse energy measured over the pseudorapidity interval 3.2--4.9 in the direction of the lead beam. A Glauber Monte Carlo analysis was used to simulate the geometry of the inelastic p+Pb collision, and the mean number of nucleon-nucleon collisions was extracted in each centrality interval. Extensions of the standard Glauber model which allow a event by event fluctuation in the nucleon-nucleon cross-section were also implemented. Geometric scaling was studied relative to the expectation from independent nucleon-nucleon collisions. Measurements of charged particle multiplicity and Z bosons indicate that considering fluctuations of the nucleon-nucleon cross section may lead to significant changes in the geometric scaling behaviour. Measurements of inclusive jet production indicate that the factorization between hard and soft processes is violated at an unexpected level.

Speaker: Mr Miguel Arratia (University of Cambridge)

Slides ATL-COM-PHYS-2014-1089.pdf

15:55 Results and future prospects of ultra-peripheral heavy-ion collisions with CMS

Ultra-peripheral collisions (UPCs) of heavy ions involve long range electromagnetic interactions at impact parameters larger than twice the nuclear radius. At TeV energies, the strong electromagnetic field due to the coherent action of the Z=82 proton charges generates a large flux of photons, which can be used for high-energy photoproduction studies. Heavy vector mesons (for example J/psi, Psi', Upsilon) produced in electromagnetic interactions provide direct information on the parton distribution functions in the nucleus at very low values of Bjorken-x. These events are characterized by a very low hadron multiplicity. The wide pseudorapidity coverage of the CMS detectors is used to separate such events from very peripheral nuclear interactions. The CMS experiment has excellent capabilities for the measurement of the heavy vector mesons in the dimuon decay channel using the tracker and the muon chambers. This analysis demonstrates CMS's capabilities for measuring J/psi and the two-photon process in ultra-peripheral collisions, using the 2011 PbPb and 2013 pPb data. The prospects for future measurements using the data to be collected in the 2015 PbPb run will be described.

Speaker: Pat Kenny

Slides diff2014UpcProspects.pdf

16:20 Vector meson photoproduction in ultra-peripheral p-Pb and Pb-Pb collisions at the LHC with the ALICE experiment

Vector mesons are copiously produced in ultra-peripheral collisions(UPC). In these collisions, the impact parameter is larger than the sum of the nuclear radii, implying that electromagnetic processes become dominant. The cross section for heavy vector meson production is expected to be sensitive to the gluon distribution and can therefore probe nuclear gluon shadowing (Pb-Pb) and the gluon structure function in the nucleon (p-Pb). The ALICE Collaboration has performed the first measurements of the $\rho^{0}$, J/$\psi$ and $\psi$(2S) UPC cross section in Pb-Pb collisions and that for exclusive J/$\psi$ photoproduction off protons in ultra-peripheral proton-lead collisions at the LHC.

Speaker: Mr Michal Broz (Comenius University)

Slides UPC.DIFF2014.pdf

16:45 → 17:00 Closing address

17:00 → 17:30 Coffee and greetings

18:30 → 21:00 Dinner