Quark Matter 2014 - XXIV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

18 May 2014, 08:00 → 24 May 2014, 13:40 Europe/Zurich

darmstadtium

Johanna Stachel (Ruprecht-Karls-Universitaet Heidelberg (DE)), Peter Braun-Munzinger (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

The Quark Matter 2014 conference is the twenty-fourth edition of the most prestigious series of international meetings in the field of ultrarelativistic heavy-ion collisions. The meetings bring together theorists and experimentalists committed to understanding the fundamental properties of strongly interacting matter at extreme energy densities. The conditions reached in head-on nuclear collisions at the highest currently available energies correspond to those in primordial matter a few tens of microseconds after the Big Bang. Thus, this type of laboratory research improves our understanding of the early phase of the Universe.
 

The first Quark Matter conference took place in 1980 in Darmstadt. Since then, the meetings of this series have been organized approximately every 1.5 years. The recent instances were in Jaipur, India (2008), Knoxville, USA (2009), Annecy, France (2011), and Washington DC, USA (2012). The current meeting brings the conference to Darmstadt again, a place with a long-standing tradition of heavy-ion research and is jointly organized by GSI Helmholtzzentrum für Schwerionenforschung GmbH, Technische Universität Darmstadt, and Universität Heidelberg.

List of Contributed Talks QuarkMatter2014_ParallelTalks.pdf

List of Posters Poster List sorted by Board-IDs Poster List sorted by Lastnames

Sunday 18 May

09:00 → 09:05 Departure of buses at darmstadtium for Student Day

09:30 → 10:30 QM check-in and access to GSI for Student Day

10:30 → 12:15 Observables and concepts

10:30 Bulk properites and hydrodynamics: Observables and concepts

Speaker: Pasi Huovinen (Johann Wolfgang Goethe-Universität)

Slides lecture.pdf

11:30 Phase diagram, fluctuations, thermodynamics, and hadron chemistry: Observables and concepts

Speaker: Claudia Ratti (Wuppertal University)

Slides QMStudents2_ratti.pdf

10:30 → 12:15 Recent developments

10:30 Bulk properties and hydrodynamics: Recent developments

Speaker: Hannah Petersen

Slides petersen_qm14_students.pdf

11:30 Phase diagram, fluctuations, thermodynamics, and hadron chemistry: Recent developments

Speaker: Alexander Philipp Kalweit (CERN)

Slides PhaseDiagramLectureQM.pdf

12:15 → 13:45 Lunch

13:45 → 15:30 Observables and concepts

13:45 Jets and high-pt probes: Observables and concepts

Speaker: Thorsten Renk (University of Jyväskylä)

Slides trenk-qm2014-student.pdf

14:45 Electromagnetic probes: Observables and concepts

Speaker: Hendrik van Hees (Goethe University Frankfurt)

Slides qm14-lect.pdf

13:45 → 15:30 Recent developments

13:45 Jets and high-pt probes: Recent developments

Speaker: Marco Van Leeuwen (University of Utrecht (NL))

Slides 14QMStudentDay_highpt_mvanleeuwen.pdf

14:45 Electromagnetic probes: Recent developments

Speaker: Klaus Johannes Reygers (Ruprecht-Karls-Universitaet Heidelberg (DE))

Slides qm2014-lecture-em-probes-recent-developments.pdf

15:30 → 16:00 Coffee break

16:00 → 20:00 Check-in

16:00 → 18:00 Observables and concepts

16:00 pA, initial state, approach to equilibrium: Observables and concepts

Slides QM2014-Salgado.key s.pdf

17:00 Heavy flavor: Observables and concepts

Speaker: Kai Schweda (Physikalisches Institut - Ruprecht-Karls-Universitat Heidelberg)

Slides QM-schweda.ppt

16:00 → 18:00 Recent developments

16:00 pA, initial state, approach to equilibrium: Recent developments

Speaker: Constantinos Loizides (Lawrence Berkeley National Lab. (US))

Slides pa-cl-qm14.pdf

17:00 Heavy flavor: Recent developments

Speaker: Enrico Scomparin (Universita e INFN (IT))

Slides Enrico_QM14.pdf Enrico_QM14.pptx

18:00 → 18:05 Departure of buses to Darmstadt city center

Monday 19 May

08:00 → 09:00 Check-in

09:00 → 10:35 Opening session

09:00 Welcome by the conference chairs P. Braun-Munzinger and J. Stachel

Slides QM2014_presentation_pbm.pdf

09:05 Welcome by Dr. B. Vierkorn-Rudolph, Federal Ministry of Education and Research

09:10 Welcome by J. Partsch, Mayor of Darmstadt

09:15 Welcome by Prof. H. J. Prömel, President of TU Darmstadt

09:20 Welcome by Prof. B. Eitel, Rector, Heidelberg University

09:25 Welcome by Prof. H. Stöcker, Scientific Director GSI

09:30 Welcome by Prof. B. Sharkov, Scientific Director FAIR

09:35 Quarks (and Glue) at Frontiers of Knowledge

Speaker: Frank Wilczek (MIT)

Slides quarkFrontiers01.pdf

10:30 → 11:00 Coffee break

11:00 → 13:00 Collective dynamics: 1

Convener: Takeshi Kodama (Universidade Federal do Rio de Janeiro)

announcement announcement-tuesday.pdf

11:00 Measurement of the centrality dependence of the charged particle pseudorapidity distribution in proton-lead collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with the ATLAS detector

Proton-lead collisions at the LHC provide an opportunity to probe the physics of the initial state of ultra-relativistic heavy ion collisions. In particular, they can provide insight on the effect of an extended nuclear target on the dynamics of soft and hard scattering processes and subsequent particle production. Charged particle multiplicity and pseudorapidity distributions are among the most basic experimental probes of particle production. The centrality dependence of the charged particle pseudorapidity distributions, dNch/deta , was measured in p+Pb collisions at a nucleon-nucleon centre-of-mass energy of sqrt(s_NN) = 5.02 TeV using the ATLAS detector. Charged particles were reconstructed over |eta| < 2.7 using the ATLAS pixel detector. The proton-lead collision centrality was characterized by the total transverse energy measured over the pseudorapidity interval 3.2 < eta < 4.9 in the direction of the lead beam. The dNch/deta distributions are found to vary strongly with centrality, with an increasing asymmetry between the proton-going and Pb-going directions as the collisions become more central. Three different calculations of the number of participants, Npart, have been carried out using a standard Glauber model as well as two Glauber-Gribov extensions. Charged particle multiplicities per participant pair are found to vary differently with Npart for these three models, highlighting the importance of the fluctuating nature of nucleon-nucleon collisions in the modeling of the initial state of p+Pb collisions.

Speaker: Ramiro Rolando Debbe Velasco (Brookhaven National Laboratory (US))

Slides RDebbeATLAS_multiplicity18MAY2014.pdf

11:20 Transverse energy distributions at mid-rapidity in $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at $\sqrt{s_{NN}} = $62.4--200 GeV and implications for particle production models

Measurements of the midrapidity transverse energy distribution $dE_T/d\eta$, are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at 62.4--200 GeV. The $E_T$ distributions are compared with the number of participants, $N_{\mathrm{part}}$, the number of binary collisions, $N_{\mathrm{coll}}$, and the number of constituent-quark participants, $N_{qp}$, calculated from a Glauber model. For Au$+$Au, $(dE_T/d\eta)/N_{\mathrm{part}}$ indicates that the two component ansatz $dE_T/d\eta ~ (1-x)N_{\mathrm{part}}/2+xN_{\mathrm{coll}}$, which has been used to explain $E_T$ distributions is simply a proxy for $N_{qp}$, and that the $N_{\mathrm{coll}}$ term does not represent a hard-scattering component in $E_T$ distributions. The $dE_T/d\eta$ distributions of Au$+$Au and $d$$+$Au are then calculated from the measured $p$$+$$p$ $E_T$ distributions using two models (additive quark model and the number-of-constituent quarks model) that both reproduce the Au$+$Au data. However, the number-of-constituent-quark-participant model agrees well with the $d$$+$Au data, while the additive quark model does not. A description of the various models and their implications will be discussed.

Speaker: Michael Tannenbaum (Brookhaven National Laboratory (US))

Slides Tannenbaum-QuarkMatter2014talk.pdf

11:40 Collective flow in small systems

The collective expansion of the fireball formed in ultrarelativistic p-A and d-A collisions are discussed. Estimates based on the extrapolation of the hydrodynamic model from A-A collisions to small systems indicate possible formation of a dense droplet of matter. Fluctuation in the initial state lead to finite eccentricity and triangularity, which give measurable elliptic and triangular flow of the emitted particles. Further predictions consistent with experimental observations are the mass ordering of the average transverse momentum and of the elliptic flow for identified particles. We discuss the prediction of the model for collisions of a deformed projectile as in d-A collisions. This deformation leads to a large elliptic flow.

Speaker: Piotr Bozek

Slides bozekqm.pdf

12:00 Light flavor hadron spectra at low-$p_{\rm T}$ and search for collective phenomena in high multiplicity pp, p-Pb and Pb-Pb collisions measured with the ALICE experiment

Comprehensive results on transverse momentum distributions, their ratios, d$N$/d$y$ and <$p_{\mathrm{T}}$> values for identified light flavor hadrons ($\pi$, K, p, $\Lambda$, $\Xi$, $\Omega$) at low $p_{\mathrm{T}}$ and mid rapidity are reported for all collision systems at LHC energies: pp, p-Pb, Pb-Pb. It is well known that strong collective effects are observed in central Pb-Pb collisions as a particle mass dependent hardening of the spectral shapes attributed to hydrodynamical flow and may be quantitatively parametrized with Boltzmann-Gibbs Blast Wave fits. In this talk, we investigate the existence of collective phenomena in small systems: pp, p-Pb and peripheral Pb-Pb where similar patterns are observed in multiplicity dependent studies. For pp collisions, measurements at three center-of-mass energies ($\sqrt{s} = $ 0.9, 2.76, 7 TeV) are presented and the evolution of the spectral shape with $\sqrt{s}$ is discussed.

Speaker: Cristian Andrei (IFIN-HH Bucharest (RO))

Slides CAndrei_QM2014.pdf

12:20 Spectra of identified particles, geometry categorization and bias, and global observables in d+Au collisions

In this talk the transverse momentum spectra of identified particles, geometry categorization and bias, and global observables in d+Au collisions at 200 GeV are reported. In d+Au collisions, the intermediate $p_T$ region between 2 and 5 GeV, there is a significant enhancement of the baryon to meson ratios relative to those measured in p+p collisions. The enhancement is present in d+Au collisions as well as Au+Au collisions and increases with centrality. We compare a class of peripheral Au+Au collisions with a class of central d+Au collisions which have a comparable number of participants and binary collisions. The $p_T$ dependent ratios for these classes display a remarkable similarity. The nuclear modification of hadrons at higher transverse momentum also reveal interesting effects. Geometry selection in d+Au/p+Pb collisions is crucial for understanding the physics underlying modified nuclear parton distribution functions, gluon saturation and glasma diagrams, initial state energy loss, and possible hydrodynamic flow in these small systems. Data from the p+Pb LHC results indicate potentially large biases in the geometry determination in these small systems. The PHENIX collaboration presents tests of auto-correlation biases. Our findings indicate that these biases are an order of magnitude smaller at RHIC as compared to the LHC, and are thus well quantified. Geometry tests with neutron-tagged events and the centrality scaling of d$N_{ch}/d\eta$ and d$E_T/d\eta$ are presented.

Speaker: Sarah Campbell (Iowa State University)

Slides QMdA6.pdf

12:40 Why is the radial flow in high multiplicity pp/pA stronger than in AA?

With growing multiplicity, the pp and pA collisions enter the domain where the macroscopic description (thermodynamics and hydrodynamics) becomes applicable. We discuss this situation, first with simplified thought experiments, then with some idealized representative cases, and finally address the real data. For clarity, we don't do it numerically but analytically, using the Gubser solution. We found that the radial flow is expected to increase from central AA to central pA. Recent CMS and ALICE data confirm that it is the case. We discuss the consequences of these finding.

Speaker: Edward Shuryak (stony brook university)

Slides shuryak_QM14.pdf shuryak_QM14.pptx

11:00 → 13:00 Electromagnetic probes: 1

Convener: Charles Gale (McGill University)

slides QM2014_announcement_reception_football.pdf

11:00 Beam energy dependence of dielectron production in Au+Au collisions from STAR at RHIC

Bulk-penetrating dielectrons allow for the extraction of direct information from all stages of a heavy ion collision as they serve as electromagnetic probes with negligible final-state interactions. The completion of the Barrel Time-of-Flight detector (TOF) in 2010 has allowed the Solenoid Tracker At RHIC (STAR) to play a unique role in the study of dielectron production with excellent particle identification, low material budget, full azimuthal acceptance at mid-rapidity, and a wide momentum coverage. In combination with the Beam Energy Scan (BES) conducted at RHIC, in particular, STAR presents the unprecedented opportunity to map out a significant portion of the QCD phase diagram within a homogeneous experimental environment. In the quest for a better understanding of strongly interacting nuclear matter the Low-Mass Region (LMR, $M_{ee}$ < 1.1 GeV/$c^2$) of dielectron spectra, on the one hand, provides information about in-medium modifications of the $\rho$-meson's properties. The Intermediate-Mass Region (IMR, 1.1 < $M_{ee}$ < 3 GeV/$c^2$), on the other hand, can provide access to the initial Quark-Gluon Plasma (QGP) temperature as well as a possibly medium-modified correlated charm continuum. In this talk, we will present the energy-dependent study of dielectron production at $\sqrt{s_{NN}}$ of 19.6, 27, 39, and 62.4 GeV. $M_{ee}$ and $p_{\text{T}}$ differential measurements of LMR mass distributions are compared to cocktail simulations of known hadronic sources. The excess yield is further compared to calculations of $\rho$ in-medium modifications. Properties of IMR spectral data will be compared to simulations of semi-leptonic charmed decays.

Speaker: Mr Patrick Huck (LBNL/CCNU)

Slides 14-05-19_HuckQM14.pdf

11:20 Dielectron measurements in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC

Electromagnetic probes are excellent messengers from the hot and dense medium created in ultra-relativistic heavy-ion collisions. Since leptons do not interact strongly, their spectra reflect the entire space-time evolution of a collision. The surrounding medium can lead to modifications of the dielectron production rate. To quantify modifications in heavy-ion collisions, measurements in pp collisions serve as a reference, while the analysis of p-A collisions allows to disentangle cold from hot nuclear matter effects. We present dielectron measurements with the ALICE central barrel detectors. The invariant mass distributions in the range $ 0 < m_{ee} < 3 $ GeV/$ c^{2} $ are compared to the expected hadronic sources for pp collisions at $ \sqrt{s}=7 $ TeV, and for p-Pb collisions at $ \sqrt{s_{\rm NN}} = 5.02$ TeV. The cross section of virtual direct photons measured in pp collisions is compared to predictions from NLO calculations as a function of the transverse momentum. Latest results of the analysis of Pb-Pb collisions at $ \sqrt{s_{\rm NN}}=2.76 $ TeV are presented.

Speaker: Markus Kohler (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

Slides mkk_QM2014.pdf

11:40 Electromagnetic emission at RHIC and LHC

I will discuss the general features of the electromagnetic radiation from QCD matter using spectral functions in the hadronic phase and the OPE expansion in the partonic phase, and use them to analyze current di-lepton and photon emissions at collider energies both at RHIC and LHC. The large low mass di-lepton enhancement and photon v2 will be addressed.

Speaker: Mr Ismail Zahed (Stony Brook University)

Slides qm14X.pptx

12:00 Thermal photon $v_3$ at LHC from event-by-event hydrodynamics

Thermal photon $v_3$ is calculated for 0--40% central collisions of Pb nuclei at LHC from event-by-event ideal hydrodynamic model [1]. The differential triangular flow parameter $v_3(p_T)$ calculated with respect to the participant plane (PP) is found to be non-zero, positive, and shows similar qualitative nature to the elliptic flow parameter $v_2(p_T)$ [2]. At $p_T=$ 1 GeV $v_3$(PP) is found to be about half of $v_2$(PP) however, for larger values of $p_T$ these two anisotropy parameters become comparable. The global geometry of the produced matter as well as the local fluctuations in the initial density distribution are responsible for this substantial value of the triangular flow parameter for thermal photons where $v_3$(PP) probes the initial state geometry in an indirect way via the generation of additional transverse flow. $v_3$ calculated with respect to the reaction plane as expected is close to zero. $v_3$(PP) strongly depends on the value of the fluctuation size parameter $\sigma$ especially in the higher $p_T$ region where, a larger $\sigma$ results in a smaller $v_3$(PP). In addition, the $v_3$(PP) is found to increase with the initial formation time of the system. [1] R. Chatterjee, D. K. Srivastava, and T. Renk, arXiv:1401.7464. [2] R. Chatterjee, H. Holopainen, I. Helenius, T. Renk, and K. J. Eskola, PRC88, 034901 (2013).

Speaker: Rupa Chatterjee

Slides qm14.pdf

12:20 Viscous corrections to photon emission in heavy-ion collisions

Photons are believed to be clean and penetrating probes of the medium created in ultra-relativistic heavy-ion collisions. The thermal photon spectrum and its anisotropy coefficients, $v_n$, are known to be very sensitive to the thermalization time, the specific shear viscosity, the equation of state of produced matter, and the initial state fluctuations [1,2]. In this talk, we will present state-of-the-art calculations of event-by-event photon emission from nuclear collisions at RHIC and LHC energies including both shear and bulk viscous corrections. Momentum spectra of thermal photons and their $p_T$-differential anisotropic flow coefficients $v_n(p_T)$ ($n$ up to 5) are computed, both with and without accounting for viscous corrections to the standard thermal emission rates. Viscous corrections to the rates are found to have a larger effect on the $v_n$ coefficients than the viscous suppression of hydrodynamic flow anisotropies. Effects from non-zero initial flow and viscous pressure tensor to photon spectra and their anisotropies are also investigated by evolving fluctuating initial density profiles with free-streaming on the event-by-event basis before matching to hydrodynamics. Complementary to the majority of hadronic observables, thermal photons provide us with additional constraints on the evolution of the viscous pressure tensor as well as the early dynamics of heavy-ion collisions. Their anisotropic flows, especially higher order $v_n$, can be used as a sensitive viscometer for the quark-gluon plasma. [1] C. Shen, U. Heinz, J.-F. Paquet and C. Gale, "Thermal photons as a quark-gluon plasma thermometer revisited", arXiv:1308.2440 [nucl-th]. [2] C. Shen, U. Heinz, J.-F. Paquet, I. Kozlov and C. Gale, "Anisotropic flow of thermal photons as a quark-gluon plasma viscometer", arXiv:1308.2111 [nucl-th].

Speaker: Chun Shen (Ohio State University)

Slides

• QM14_ChunShen.pdf
• QM14_ChunShen_picture.pdf
• QM14_ChunShen_picture.pptx

Video hadrons_vs_photons.avi

12:40 Photon suppression and dilepton enhancement in semi-QGP

Experimental measurements of photon collective flow have obtained v2 comparable to those of hadrons. This favors a scenario of hadron dominated medium in photon production. A realistic calculation of photon rate in QGP phase is important to scrutinize this scenario. Fire ball produced in RHIC and LHC is close to semi-QGP which has a non-trivial value of Polyakov loop. We calculated the photon rate in the semi-QGP and found indeed a suppression of the photon rate due to non-trivial Polyakov loop, as compared to standard thermal perturbative results. We also calculated dilepton rate in the same semi-QGP. On the contrary, we found non-trivial Polyakov loop enhances the dilepton rate. This implies the v2 of dilepton distinguishes from that of photon.

Speaker: Shu Lin (RIKEN BNL)

Slides Photon_and_dilepton_in_semi-QGP.pdf

11:00 → 13:00 Initial state physics: 1

Convener: Carlos Pajares (University Santiago de Compostela)

slides QM2014_announcement_reception_football.pdf

11:00 The ridge through Colored Glass

The ridge in pp, p/d+A and A+A collisions manifest at very high multiplicities. Regardless of whether initial state or final state effects dominate, the physics of very high parton densities is relevant. In this talk, we attempt a synthesis of the state-of-the art in the CGC approach to computing both initial state and final state effects that generate collimated long range rapidity correlations. The emphasis throughout will be on a) quantitative comparisons to data, and b) on open problems in the different approaches that become manifest through such comparisons. We will discuss future measurements that are likely to provide definitive answers regarding the physics underlying this remarkable phenomenon. References: 1) K. Dusling and R. Venugopalan, ``Initial state triangular azimuthal anisotropy in p+A and A+A collisions",in preparation. 2) B. Schenke, P. Tribedy, and R. Venugopalan, ``Multiplicity constrained v_n moments in pA and AA collisions in the IP-Glasma model", in preparation. 3) B.~ Schenke, P. Tribedy and R. Venugopalan, ``Multiplicity distributions in p+p, p+A and A+A collisions from Yang-Mills dynamics,'' Phys.\ Rev.\ C {\bf 89}, 024901 (2014). 4)A. Bzdak, B. Schenke, P. Tribedy and R. Venugopalan,``Initial state geometry and the role of hydrodynamics in proton-proton, proton-nucleus and deuteron-nucleus collisions,''Phys.\ Rev.\ C {\bf 87}, 064906 (2013).

Speaker: Raju Venugopalan

Slides QM2014_raju-venugopalan.pdf

11:20 Higher harmonics from intrinsic multi-particle production

We explore the detailed structure of the {\em ridge} in the Color-Glass-Condensate (CGC) effective field theory of QCD and demonstrate a novel mechanism that produces a non-vanishing $v_3$ without final-state re-scattering. A $v_3$ in agreement with the LHC p+Pb data is generated by the interference of diagrams attributed to the jet (away-side) and ridge (near-side) substructure of the azimuthal correlation. We also find that the $v_3$ in p+A is comparable to that in A+A for similar multiplicities.

Speaker: Kevin Dusling

Slides QM14_Dusling.pdf

11:40 Initial state geometry and fluctuations in deformed and asymmetric nuclear collisions in the IP-Glasma framework

The IP-Glasma model of initial conditions based on the *ab initio* color glass condensate (CGC) framework successfully explains the bulk features of global data for various systems like p+p, p+A and A+A over a wide range of energies [1-3]. We employ this framework to study deformed U+U collisions, asymmetric Cu+Au collisions and the effect of deformation in Au+Au collisions at RHIC. A combined study of these heavy ion systems with varying initial geometries can provide a unique opportunity to determine the origin of different sources of fluctuations that affect global observables like multiplicity and flow. We study the sensitivity of multiplicity, eccentricity and their event-by-event distributions to the details of initial state geometry. Results are compared to a two component MC-Glauber model implementation that includes Negative-Binomial multiplicity fluctuations. We argue that measurements of global observables for these systems at RHIC can constrain the mechanism of multi-particle production [4]. Ref : [1]B .Schenke, P. Tribedy, R. Venugopalan, Phys. Rev. Lett. 108 (2012) 252301, Phys.Rev. C89 (2014) 024901. [2]C. Gale, S. Jeon, B. Schenke, P. Tribedy, R. Venugopalan, Phys.Rev.Lett. 110 (2013) 012302. [3]A. Bzdak, B. Schenke, P. Tribedy, R. Venugopalan, Phys. Rev. C 87, 064906 (2013). [4]B .Schenke, P. Tribedy, R. Venugopalan *in preparation*

Speaker: Prithwish Tribedy (VECC)

Slides tribedy_qm2014.pdf

12:00 Flow measurements and selection of body-body and tip-tip enhanced samples in U+U collisions at STAR

The azimuthal anisotropy of particle production is commonly used in high-energy nuclear collisions to study the early evolution of the expanding system. The prolate shape of uranium nuclei provides the possibility to study how the initial geometry of the nuclei affects the azimuthal distributions. It also provides a unique opportunity to understand the initial conditions for particle production at mid-rapidity in heavy ion collisions. In this talk, the two- and four- particle cumulant, $v_2$($v_2{2}$ and $v_2{4}$), from U+U collisions at $\sqrt{s_{NN}}=$ 193 GeV and Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV for inclusive charged hadrons will be presented. The STAR Zero Degree Calorimeter is used to subdivide the 0-1% centrality bin into even finer centralities. Differences were observed between the multiplicity dependence of $v_2{2}$ for most central Au+Au and U+U collisions. Data was compared with a Monte Carlo Glauber model and it was seen that this model cannot explain the multiplicity dependence of $v_2{2}$ in central collisions. It has also been demonstrated that ZDC and multiplicity in combination provide a way to select body-body or tip-tip enhanced samples of central U+U collisions. We will also present preliminary $v_1$ and $v_2$ results for inclusive charged hadrons from Au+Au and U+U collisions, with the first-order event plane determining from spectator neutrons. This type of event plane represents the reaction plane instead of the participant plane as used in other methods, this analysis provides an alternative approach to examine the eccentricity-scaling to reveal the QGP properties.

Speaker: Hui Wang (Brookhaven National Lab)

Slides QM_Hui_v5.pptx

12:20 Photonuclear production of vector mesons in ultra-peripheral Pb-Pb collisions at the LHC

Vector mesons are copiously produced in ultra-peripheral nucleus-nucleus collisions. In these collisions, the nuclei are separated by impact parameters larger than the sum of the nuclear radii, and the interaction is mediated by the electromagnetic field. The interaction effectively corresponds to a photonuclear interaction between a photon, generated from the electromagnetic field of one of the nuclei, and the target nucleus. The ALICE Collaboration has previously published results on exclusive J/$\psi$ photoproduction at mid and forward rapidities in Pb-Pb collisions. The cross section for this process is a particularly good measure of the nuclear gluon distribution. In this talk, the latest results on exclusive production of light and heavy vector mesons from ALICE in Pb-Pb collisions will be presented.

Speaker: Joakim Nystrand (University of Bergen (NO))

Slides NystrandALICEQM14.pdf

12:40 Double-parton scatterings in proton-nucleus and nucleus-nucleus collisions at the LHC

We have derived a simple generic expression to compute the cross sections for double-parton scatterings (DPS) in high-energy proton-nucleus and nucleus-nucleus collisions as a function of the corresponding single-parton hard cross sections [1,2]. Estimates of DPS contributions at LHC energies for (i) same-sign W-boson pair production in p-Pb, and (ii) double-J/$\psi$ production in Pb-Pb, are obtained from NLO predictions with nuclear PDF modifications for the corresponding single-parton scatterings. The first process can help determine the effective $\sigma_{\rm eff}$ parameter characterising the transverse distribution of partons in the nucleon, whereas the second one provides interesting insights on the event-by-event dynamics of J/$\psi$ production in Pb-Pb. The expected cross sections and event rates after typical acceptance and efficiency losses, for various others DPS processes involving quarkonia, jets, and gauge bosons ($\gamma$, W, Z) will be given for p-Pb and Pb-Pb collisions at the LHC. [1] D. d'Enterria, A. Snigirev, Phys.Lett. B718 (2013) 1395 [2] D. d'Enterria, A. Snigirev, Phys.Lett. B727 (2013) 157

Speaker: David d'Enterria (CERN)

Slides dde_DPS_pA_AA_QM14.pdf

11:00 → 13:00 Heavy flavor: 1

Convener: Joerg Aichelin (University of Nantes)

announcement QM2014_announcement_Wed.pdf

11:00 Theoretical predictions of jet suppression: a systematic comparison with RHIC and LHC data

Accurate theoretical predictions of jet suppression are necessary for studying the properties of QCD matter created in ultra-relativistic heavy ion collisions. However, testing the prediction accuracy - and extracting useful qualitative knowledge - is often limited by constraining the predictions to only few experimental probes at a time, and by using free parameters. To address this issue, we will present comprehensive suppression predictions, which run across all available probes and different centrality regions at RHIC and LHC. To generate these predictions, we use the finite size dynamical QCD formalism that we previously developed, together with its recent extensions to finite magnetic mass [1] and running coupling [2]; this formalism is integrated into a numerical procedure that uses no free parameters in model testing. We obtain a very good agreement with the experimental results across all particle species [2,3], for different centrality regions [4], and for both RHIC and LHC. We will also discuss improved qualitative understanding of the relevant experimental data, which follows from such comprehensive comparison. 1. M. Djordjevic and M. Djordjevic, Physics Letters B 709, 229 (2012). 2. M. Djordjevic and M. Djordjevic, arXiv:1307.4098 3. M. Djordjevic, Phys.Rev.Lett. 112, 042302 (2014). 4. M. Djordjevic, M. Djordjevic and B. Blagojevic, to be submitted.

Speaker: Dr Magdalena Djordjevic (Institute of Physics Belgrade, University of Belgrade)

Slides MDjordjevic_QM2014.pptx

11:20 Heavy quark physics measurements with the PHENIX Detector

In heavy ion collisions at RHIC, heavy quarks are produced predominantly in the initial hard scatterings and thus probe the entire lifetime of the hot and dense medium. Additionally, measuring charm and beauty quarks allows us to study the mass dependence of energy loss, constraining the transport properties of the Quark-Gluon Plasma. Previous measurements at RHIC have shown large suppression and azimuthal anisotopy of open heavy flavor hadrons. In order to further constrain medium properties using heavy flavor probes, the interaction of charm and beauty quarks must be measured separately. PHENIX presents new results on heavy quark physics via single leptons, dilelectron correlations, electron-muon correlations, and tagging with displaced vertices.

Speaker: Alan Dion (Stony Brook University)

Slides qm2014_Dion.pdf

11:40 Heavy-flavour production and nuclear modification factor in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ =2.76 TeV with ALICE

Heavy quarks (charm and beauty) are considered effective probes to investigate the properties of the strongly-interacting medium formed in high energy nuclear collisions. Heavy quarks lose energy interacting with the medium via inelastic processes (medium-induced gluon radiation) and elastic collisions. The nuclear modification factor, $R_{\rm AA}$, defined as the ratio of the heavy-flavour production yield in nucleus-nucleus collisions to the binary scaled pp one, is an observable sensitive to in-medium energy loss. In particular, the comparison of the $R_{\rm AA}$ of charm, beauty and light-flavour hadrons provides information about the colour charge and parton mass dependence of the energy loss. Open heavy-flavour production was measured with ALICE in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76~\mathrm{TeV}$ using D mesons ($ {\rm D^0} $, ${\rm D^{*+}}$, $ {\rm D^{+}} $ and ${\rm D_s^+}$ ) reconstructed from their hadronic decays and electrons from heavy-flavour decays at central rapidity, and muons from heavy-flavour decays at forward rapidity. The D meson and heavy-flavour decay leptons differential $ R_{ \rm AA } $ measurements, namely the transverse momentum, rapidity and centrality dependence, will be shown. The comparison of the nuclear modification factors of strange and non-strange D mesons will be presented, as well as the ${\rm D^0}$ $R_{\rm AA}$ measured in different azimuthal regions with respect to the reaction plane of the collision. The D meson $R_{\rm AA}$ will be compared with light-flavour and non-prompt ${\rm J}/\psi$ results (from the CMS experiment). In addition, the heavy-flavour $R_{\rm AA}$ and $v_2$ will be compared to results from Au-Au collisions at $\sqrt{s_{\rm NN}}=200~\mathrm{GeV}$ measured at RHIC. Finally, the heavy-flavour measurements will be compared to theoretical models.

Speaker: Andrea Festanti (Universita e INFN (IT))

Slides HFinPbPb_AFestanti_QM2014.pdf

12:00 Open charmed hadron production in p+p, Au+Au and U+U collisions at STAR

Heavy quarks are dominantly produced from initial hard scatterings in high-energy heavy ion collisions, and their interaction with QCD medium is sensitive to the medium dynamics. Thus heavy quarks are suggested as excellent probes to study the properties of the hot and dense nuclear matter created at the Relativistic Heavy Ion Collider. In this talk, we present the first results of open charm meson production in U+U collisions at $\sqrt{s_{NN}}$=193 GeV from the STAR experiment. We also report on updated results in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV, and those in p+p collisions at $\sqrt{s}$=200 GeV and 500 GeV. In these measurements, $D^{0}$ and $D^{*}$ mesons are reconstructed through hadronic decay channels. For both U+U and Au+Au collisions, invariant $D^{0}$ meson production yields are determined from minbias and 0-10$\%$ central triggered events for the $p_{T}$ range from 0 to 6 GeV/c. For p+p collisions, events with high $E_{T}$ triggers are used to extend the $p_{T}$ range of the measured cross section up to 10 GeV/c at $\sqrt{s}$=200 GeV and to 18 GeV/c at $\sqrt{s}$=500 GeV, respectively. Nuclear modification factors ($R_{AA}$) of open charm mesons are extracted from these results and are compared to various theoretical model calculations.

Speaker: Prof. Zhenyu Ye (University of Illinois at Chicago)

Slides yezhenyu_QM2014_v7.pdf

12:20 Measurement of single electrons from heavy flavor decays from $p$$+$$p$, $d$$+$Au, and Cu$+$Cu collisions in the PHENIX experiment

Charm and bottom quarks are formed predominantly by gluon fusion in the initial hard scatterings at RHIC, making them good probes of the full medium evolution. Previous measurements at RHIC have shown large suppression and azimuthal anisotopy of open heavy flavor hadrons in Au$+$Au collisions at $\sqrt{s_{NN}} = 200$ GeV. Explaining the simultaneously large suppression and flow of heavy quarks has been a challenge for the community. To further understand the heavy flavor transport in the hot medium, it is imperative to also measure cold nuclear matter effects which affect the initial distribution of heavy quarks as well as the system size dependence of the final state suppression. In this talk, new measurements by the PHENIX collaboration of single electrons from heavy flavor decays in $p$$+$$p$, $d$$+$Au, and Cu$+$Cu collisions at $\sqrt{s_{NN}} = 200$ GeV are presented. In particular, surprising enhancement of intermediate transverse momentum heavy flavor leptons in d$+$Au at mid and backward rapidity are seen to grow going to mid-central Cu$+$Cu collisions. This enhancement is much larger than anti-shadowing of the parton distributions and is theoretically unexplained.

Speaker: Sanghoon Lim (Yonsei University)

Slides QM14_talk_shlim_v4.pdf

12:40 Heavy-flavour elliptic flow in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV measured with ALICE at the LHC

The main purpose of ALICE at the LHC is to investigate the properties of the deconfined state of strongly-interacting matter produced in high-energy heavy-ion collisions. Since heavy quarks, i.e. charm and beauty, are produced on a shorter time scale with respect to the hot fireball, they are suited to probe the interaction dynamics inside the medium. The ALICE collaboration has measured the production of open heavy-flavour hadrons via their hadronic and semi-electronic decays at mid-rapidity and via the semi-muonic decay channel at forward rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV. The azimuthal distribution of heavy-flavour hadrons reflects the initial spatial anisotropy of the heavy-ion collision in case of sufficient re-scattering of the heavy quarks in the hot and dense matter. Therefore the heavy-flavour elliptic flow, the second harmonic in the Fourier expansion of the particle azimuthal distribution, is an observable sensitive to the degree of thermalization of charm and beauty quarks in the medium at low $p_{\rm T}$, as well as to the path length dependence of the energy loss of heavy quarks at high $p_{\rm T}$. The elliptic flow measurements are presented for prompt charm mesons, i.e D$^{0}$, D$^{+}$, D$^{*+}$, and heavy-flavour decay electrons at mid-rapidity, as well as for heavy-flavour decay muons at forward rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV for various centrality intervals. The results will be compared with corresponding measurements of other hadron species. Results of the D-meson nuclear modification factor measured in the direction of the reaction plane and orthogonal to it will be also shown. Comparisons with model calculations will be discussed.

Speaker: Raphaelle Bailhache (Johann-Wolfgang-Goethe Univ. (DE))

Slides summarybis_copyy.pdf

13:00 → 14:20 Lunch

14:20 → 16:05 Collective dynamics: 2

Convener: Laszlo Csernai (Department of Physics and Technology)

announcement announcement-tuesday.pdf

14:20 Beam energy dependence of the viscous damping of anisotropic flow

The flow harmonics $v_{2,3}$ for charged hadrons, are studied for a broad range of centrality selections and beam collision energies in Au+Au ($\sqrt{s_{NN}}= 7.7 - 200$ GeV) and Pb+Pb ($\sqrt{s_{NN}}= 2.76$ TeV) collisions. They validate the characteristic signature expected for the system size dependence of viscous damping at each collision energy studied. The extracted viscous coefficients, that encode the magnitude of the ratio of shear viscosity to entropy density $\eta/s$, are observed to decrease to an apparent minimum as the collision energy is increased from $\sqrt{s_{NN}}= 7.7$ to approximately 62.4~GeV; thereafter, they show a slow increase with $\sqrt{s_{NN}}$ up to 2.76 TeV. This pattern of viscous damping provides the first experimental constraint for $\eta/s$ in the temperature-baryon chemical potential ($T, \mu_B$) plane, and could be an initial indication for decay trajectories which lie close to the critical end point in the phase diagram for nuclear matter.

Speaker: Roy Lacey (Stony Brook University)

Slides Lacey_QM2014.pdf Lacey_QM2014.pptx

14:40 Elliptic flow of identifed particles in Pb-Pb collisions at the LHC

We report the measurements of elliptic flow for identified particles produced in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV with the ALICE detector at the LHC. The second Fourier coefficient, $v_2$, measured with the scalar product method with a large pseudo-rapidity gap of $|\Delta\eta| > 2.0$, is reported for $\pi$, ${\rm K}^{\pm}$, ${\rm K}^0_s$, p ($\overline{\mathrm{p}}$), $\phi$, $\Lambda$ ($\overline{\mathrm{\Lambda}}$), $\Xi$ and $\Omega$. We will present the transverse momentum $p_{\mathrm{T}}$ dependence of the $v_2$ of each particle for several centrality classes. In the low $p_{\mathrm{T}}$ region ($p_{\mathrm{T}} < 2$ GeV/$c$) our data are described fairly well by hydrodynamical calculations. We will discuss our results in the intermediate $p_{\mathrm{T}}$ region $2 < p_{\mathrm{T}} < 5$ GeV/$c$, where the scaling with the number of constituent quarks was first reported at RHIC energies.

Speaker: Alexandru Florin Dobrin (University of Utrecht (NL))

Slides dobrin_PIDv2QM14.pdf

15:00 Elliptic flow of light nuclei and identified hadrons, their centrality and energy dependence in STAR

A strongly interacting medium, namely Quark Gluon Plasma (QGP), is formed in high energy heavy ion collisions at RHIC. Elliptic flow $(v_{2})$, the second order Fourier coefficient of azimuthal distribution of the produced particles with respect to reaction plane, is used to investigate the properties of QGP. Light nuclei ($d$, $\bar{d}$, $t$, $^{\small{3}}He$), produced in such collisions, are believed to be formed by coalescence of nucleons. By comparing $v_{2}$ of light nuclei with their constituents, we can understand the production mechanism of nuclei in heavy ion collisions. At top RHIC energies, identified hadron $v_{2}$ revealed many features like the number-of-constituent quark (NCQ) scaling and mass ordering. With the combined statistics, we can test the scaling behaviors for rare multi-strange particles ($\phi$, $\Xi $ and $\Omega$). An energy dependent difference in $v_{2}$ ($\Delta v_{2}$) between particles and anti-particles was also observed in beam energy scan data at STAR. In this talk, we show the $p_{T}$ and centrality dependence of $v_{2}$ of light nuclei ($d$, $\bar{d}$, $t$, $^{3}He$), and identified hadrons ($\pi^{\pm}$, $K^{\pm}$, $K_{s}^{0}$, $p$, $\bar{p}$, $\phi$, $\Lambda$, $\bar{\Lambda}$, $\Xi^{\pm}$, $\Omega^{\pm}$) at mid-rapidity for Au+Au collisions at $\sqrt{s_{NN}}\ =\ 7.7,\ 11.5,\ 19.6,\ 27,\ 39,\ 62.4$ and $200$ GeV from STAR. Light nuclei and hadrons are identified using the time projection chamber and time-of-flight detector systems of STAR. The mass number and constituent quark scaling of nuclei $v_{2}$ will be presented. Light nuclei $v_{2}$ will be compared to those from $p$($\bar{p}$) and to a coalescence model calculation using the phase space distributions of produced nucleons in a transport model. The centrality dependence of $\Delta v_{2}$ for identified hadron will be shown and compared to model calculations. We further discuss NCQ scaling and mass ordering of multi-strange hadron $v_{2}$ at the top energy Au+Au collisions at RHIC.

Speaker: Md. Rihan Haque (V)

Slides QM14_nuclei_hadron_ver4.pdf

15:20 Viscous hydrodynamics for systems undergoing strongly anisotropic expansion

The collective expansion in relativistic heavy-ion collisions is initially highly anisotropic. Due to viscosity, this leads to strongly deformed local momentum distributions which invalidates the standard viscous hydrodynamic expansion around a local equilibrium distribution, causing a breakdown of viscous fluid dynamics à la Israel and Stewart at early times. We have developed an improved formulation of viscous hydrodynamics [1] that is based on an expansion around a spheroidally deformed local momentum distribution. A spheroidal local momentum distribution leads to the "anisotropic hydrodynamics" developed earlier by Martinez and Strickland, which accounts non-perturbatively for the resulting large early-time anisotropy between the longitudinal and transverse pressures. By allowing in our new treatment for additional small deviations of the local momentum distribution from spheroidal symmetry, we arrive at a complete formulation of second-order viscous hydrodynamics in which the large longitudinal-transverse momentum anisotropy is treated non-perturbatively à la Martinez and Strickland while the smaller remaining viscous stress components are treated perturbatively à la Israel and Stewart. We perform a test of the approach for a system undergoing boost-invariant longitudinal expansion without transverse expansion which maximizes the longitudinal-transverse pressure anisotropy. For this system the Boltzmann equation can be solved exactly in the relaxation-time approximation, allowing for a quantitative test of effective macroscopic hydrodynamic theories. We find that the viscous anisotropic hydrodynamic framework ("vaHydro") significantly outperforms all other available hydrodynamic descriptions, for both small and large values of the shear viscosity $\eta/s$. We expect vaHydro to provide a superior description also after including transverse expansion and to allow for an earlier matching of pre-equilibrium dynamics to hydrodynamics, due to the superior ability of vaHydro to handle the large differences in longitudinal and transverse expansion rates at early times. [1] D. Bazow, U. Heinz, M. Strickland, arXiv:1311.6720, Phys. Rev. C, in press.

Speaker: Ulrich Heinz (The Ohio State University)

Slides QM2014_Heinz.pdf

15:40 Extracting the bulk viscosity of the quark-gluon plasma

Currently, most fluid-dynamical simulations of relativistic heavy ion collisions take into account only dissipative effects originating from shear viscosity. However, there is no a priori reason to neglect bulk viscosity since the actual order of magnitude and temperature dependence of this transport coefficient is unknown, and could be significant. In this work, we explore the phenomenological implications of a nonzero bulk viscosity coefficient on transverse momentum spectra and azimuthal momentum anisotropy. We then extract the optimal values of the bulk and shear viscosity coefficients that are able to describe these observables. For ultracentral heavy ion collisions, measured by ATLAS and CMS, we perform this analysis using several initial condition models. For other centrality classes, we determine these coefficients using the IP-Glasma initial condition model. Our fluid-dynamical description is the most complete available and includes all possible second order terms that appear in Israel-Stewart theory, including those that couple bulk viscous pressure to shear stress. The transport coefficients of all terms are computed using kinetic theory. We find that the optimum values of shear viscosity extracted from data can be modified up to 50% when bulk viscosity is included. We further discuss the effects of baryon chemical potential on the shear viscosity of bulk nuclear matter. We show that a hadron resonance gas with large baryon number density is closer to the ideal fluid limit than the corresponding gas with zero baryon number.

Speaker: Dr Gabriel Denicol (McGill University)

Slides Denicol_QM_2014_v3.pdf

14:20 → 16:00 Electromagnetic probes: 2

Convener: Thomas Peitzmann (University of Utrecht (NL))

slides QM2014_announcement_reception_football.pdf

14:20 Centrality dependence of soft photon production and its collective flow in Au$+$Au collisions at $\sqrt{s_{NN}} = 200$ GeV

Soft photons are of particular interest since they are unmodified once produced, and thus carry information about the space-time thermal properties of the medium. We present new results on the centrality dependence of soft single photons in Au$+$Au collisions, down to $p_T = 400$ MeV/$c$ via photon conversions to $e^+e^-$ pairs. These measurements provide stringent tests of the hydrodynamic space-time evolution as a detailed function of the collision geometry. These soft photons have different angular emission patterns depending on their production mechanism. Previous published PHENIX results indicate that the second order Fourier coefficient ($v_2$) is postive for $p_T < 4$ GeV/$c$, which is qualitatively explained by hydrodynamical model calculations, but not quantitatively. The 3\textsuperscript{rd} order Fourier coefficient ($v_3$) of photons has been proposed as a critical additional handle to understand the photon emission. Photons emitted under the presence of strong magnetic field created in the collision would have a significant influence on $v_2$ while very little on $v_3$. In contrast, hydrodynamical models predict a sizable photon $v_3$. We report the latest results on the centrality dependence of the soft photon production and the $v_2$ and $v_3$ coefficients in Au$+$Au collisions at $\sqrt{s_{NN}} = 200$ GeV.

Speaker: Sanshiro Mizuno (University of Tsukuba (JP))

Slides QM_photon_vn_Sanshiro_last2.pdf

14:40 Direct virtual photon and dielectron production in Au+Au collisions at $ \sqrt{s_{NN}} $ = 200 GeV at STAR

One important physics goal of ultra-relativistic heavy-ion collisions is to study the fundamental properties of a hot, dense medium created in these collisions. This medium is expected to emit thermal radiation which is in the form of direct photons and dileptons. Once produced, photons and leptons traverse the strongly interacting medium with minimal interactions. The fully installed Time-of-Flight Detector in 2010 enables clean electron identification from low to intermediate transverse momentum ($p_{T}$). In this talk, we will present the direct virtual photon production for 1<$p_{T}$<5 GeV/$c$ derived from the dielectron continuum in the dielectron invariant mass region 0.1<$M_{ee}$<0.3 GeV/$c^{2}$ from one billion $\sqrt{s_{NN}}$ = 200 GeV Au+Au minimum bias events taken in 2010 and 2011. In addition, we will present the centrality and $p_{T}$ dependence of dielectron production and the dielectron azimuthal angle correlation in the intermediate mass(1.1<$M_{ee}$<3 GeV/$c^{2}$) region in this dataset. The relevant results from $\sqrt{s}$ = 200 GeV p+p collisions taken in 2012 will also be discussed. Comparisons to model calculations including hadronic and partonic thermal radiation will be made for both the direct virtual photon and dielectron production in Au+Au collisions.

Speaker: Chi Yang (USTC/BNL)

Slides ChiYang_QM14.pdf

15:00 Direct-photon spectra and flow in Pb-Pb collisions at the LHC measured with the ALICE experiment

Unlike hadrons, direct photons are produced in all stages of a nucleus-nucleus collision and therefore test our understanding of the space-time evolution of the produced medium. Of particular interest are so-called thermal photons expected to be produced in a quark-gluon plasma and the subsequent hadron gas. The transverse momentum spectrum of thermal photons carries information about the temperature of the emitting medium. The effect of Doppler blueshift on photons spectra from later and colder stages of a collision, however, potentially complicates the extraction of the temperature. In this presentation, direct-photon spectra in the range $1 < p_T < 12$ GeV/c from Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV will be shown. The results were obtained with two independent methods: by measuring photons with the electromagnetic calorimeter PHOS and by measuring $e^+e^-$ pairs from external conversions of photons in the detector material. The measured direct-photon spectra will be compared with predictions from state-of-the-art hydrodynamic models. In addition, direct-photon production in p-Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV will be discussed. In the standard hydrodynamical modeling of nucleus-nucleus collisions, thermal photons mostly come from the early hot stage of the collision. As collective hydrodynamic flow needs time to build up, the azimuthal anisotropy of thermal photons quantified with Fourier coefficient $v_2$ is expected to be smaller than the one for hadrons. However, the PHENIX experiment and ALICE experiment observed $v_2$ values of direct-photons similar in magnitude to the pion $v_2$. These unexpected observations constitute the so called "direct-photon flow puzzle" as they challenge the standard hydrodynamic picture of nucleus-nucleus collisions and/or the standard photon emissions rates in the quark-gluon plasma and the hadron gas. We will present the inclusive photon $v_2$ and $v_3$ in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV in the range $1 < p_T < 5$ GeV/c and discuss implications for the $v_2$ and $v_3$ of direct-photons.

Speaker: Friederike Bock (Ruprecht-Karls-Universitaet Heidelberg (DE))

Slides QM_DirectPhoton_v4.pdf

15:20 Critical enhancement of thermal photons

A relatively small spectral slope and large elliptic flow of direct photons measured at RHIC and LHC has reignited the discussion of thermal photons as a probe of the quark-gluon plasma (QGP). We present a systematic discussion of the macro- and micro-physics that figures into calculating thermal emission spectra. For the bulk medium we compare the temperature and flow evolution in fireball [1] and hydrodynamic approaches [2], and study how different tunes of initial conditions, compatible with bulk hadron observables, affect the photon spectra. We deduce evidence for an enhancement of currently available hadronic and QGP emission rates around Tc, and a potential suppression of early QGP radiation (indicative for a gluon-rich early QGP). We then present an updated (more complete) assessment of hadronic emission channels involving meson exchange reactions in baryon-meson scattering which have not been considered thus far [3]. We also investigate consequences for thermal dilepton v2. [1] H. van Hees, C. Gale and R. Rapp, Phys. Rev. C 84 (2011) 054906 [2] H. van Hees, M. He and R. Rapp, in preparation. [3] N. Holt and R. Rapp, work in progress.

Speaker: Prof. Ralf Rapp (Texas A&M University)

Slides QM14_2.pdf QM14_2.ppt

15:40 Probing the non-equilibrium dynamics of hot and dense QCD with dileptons

Much work has been devoted to the determination of an effective value of the shear viscosity coefficient from analyses of the hadronic final states in relativistic heavy-ion collisions. Electromagnetic radiation, however, constitutes a class of complementary and penetrating probes that are sensitive to the entire space-time history of nuclear collisions including its very early stages. We show that thermal dileptons (and photons) are affected by the transport properties of the fluid and by the non-equilibrium aspects of the initial state that are usually inaccessible to hadronic probes. For the first time, we explicitly demonstrate that electromagnetic spectra and azimuthal momentum anisotropy can be used not only to investigate the magnitude of the shear relaxation time and to differentiate between possible initial shear-stress tensors, but also to reveal the temperature dependence of the shear viscosity coefficient. We further show that the dependence of electromagnetic probes on these quantities comes mostly from processes occurring in the QGP phase. Our approach utilizes event-by-event 3+1D viscous hydrodynamic simulations (MUSIC) [1], and the dilepton emission sources include contributions from charm decay and hadronic rates extracted from in-medium spectral functions [2]. [1] Bjoern Schenke, Sangyong Jeon, Charles Gale, Phys.Rev. C82 (2010) 014903 [2] Gojko Vujanovic, Clint Young, Bjoern Schenke, Ralf Rapp, Sangyong Jeon, and Charles Gale, arXiv:1312.0676, PRC in press.

Speaker: Gojko Vujanovic (McGill University)

Slides Vujanovic_QM14_v7.pdf

14:20 → 16:00 Approach to equilibrium

Convener: Urs Wiedemann (CERN)

14:20 Early isotropization of the quark-gluon plasma

In recent years, the problem of thermalization in Heavy Ion Collision has received much attention, but has yet to be solved. The issue is the following: on one hand, viscous hydrodynamics simulations suggest that the matter produced in such collisions (called the Quark Gluon Plasma, or QGP) behaves like a nearly perfect fluid, and does so very shortly after the collision (around 1 fm/c). Since hydrodynamics has local thermal equilibrium in its prerequisites, this tends to show that the QGP has thermalized during the very early stages of the collision. On the other hand, theoretical models (based on microscopic theories like the Color Glass Condensate, or CGC) predict that the QGP is very far from local thermal equilibrium at the initial time (among other non-thermal features, its energy-momentum tensor is very anisotropic). One of the approaches developed to study this non-perturbative problem in QCD is a resummation scheme that amounts to averaging over classical fields, with random initial conditions given by a one loop calculation in the CGC framework. We present here the results that we obtained by following this approach – the so-called classical statistical approximation or CSA, showing an early isotropization of the system compatible with viscous hydrodynamics. As a final remark, some recently found theoretical limitations of the CSA will be briefly mentioned.

Speaker: Thomas Epelbaum (IPhT)

Slides Epelbaum_QM14.pdf

14:40 Equilibration of anisotropic quark-gluon plasma produced by decays of color flux tubes

A set of kinetic equations is used to study equilibration of the anisotropic quark-gluon plasma produced by decays of color flux tubes possibly created at the very early stages of ultra-relativistic heavy-ion collisions. The decay rates of the initial color fields are given by the Schwinger formula, and the collision terms are treated in the relaxation-time approximation. By connecting the relaxation time with viscosity we are able to study production and thermalization processes in the plasma characterized by different values of the ratio of the shear viscosity to entropy density, ${\bar \eta}$. For the lowest (KSS) value of this ratio, $4\pi{\bar \eta} = 1$, and realistic initial conditions for the fields, the system approaches the viscous-hydrodynamics regime within 1--2 fm/c. On the other hand, for larger values of the viscosity, $4\pi{\bar \eta} \geq 3$, the collisions in the plasma become inefficient to destroy collective phenomena which manifest themselves as oscillations of different plasma parameters. The presence of such oscillations brings in differences between the kinetic and hydrodynamic descriptions, which suggest that the viscous-hydrodynamics approach after 1--2 fm/c is not complete if $4\pi{\bar \eta} \geq 3$ and should be extended to include dissipative phenomena connected with color conductivity. Presentation based on the article published as Phys. Rev. D88 (2013) 034028

Speaker: Wojciech Florkowski (Institute of nuclear Physics, Krakow)

Slides florkowski-qm-14.pdf

15:00 Turbulent thermalization process in heavy-ion collisions at ultrarelativistic energies

When and to what extent a thermalized Quark Gluon Plasma is achieved in heavy-ion collision impacts the quantitative extraction of transport properties in the QGP. We address this problem by employing the largest to date real time classical-statistical lattice simulations. Most remarkably, we find that the thermalization process is governed by a universal attractor, where the space-time evolution of the plasma becomes independent of the initial conditions [1,2]. In this classical regime, the plasma exhibits the self-similar dynamics characteristic of wave turbulence, as observed in a large variety of strongly correlated many-body systems. We interpret the consequences of our numerical lattice results for thermalization in heavy-ion experiments. [1] J.Berges,K.Boguslavski,S.Schlichting,R.Venugopalan; arXiv:1303.5650 [hep-ph]. [2] J.Berges,K.Boguslavski,S.Schlichting,R.Venugopalan; arXiv:1311.3005 [hep-ph].

Speaker: Dr Sören Schlichting (Brookhaven National Lab)

Slides QM2014_SchlichtingFINAL.pdf

15:20 Structure of chromomagnetic fields in the glasma

The initial stage of a heavy ion collision is dominated by nonperturbatively strong chromoelectric and -magnetic fields. The properties of these fields can be calculated numerically using the CGC description of the small x degrees of freedom of the colliding nuclei. The spatial Wilson loop provides a gauge invariant observable to probe the dynamics of the longitudinal chromomagnetic field. This talk describes the results from a recent real time lattice calculation (arXiv:1401.4124) of the area-dependence of the expectation value of the spatial Wilson loop. We consider ensembles of gauge field configurations generated from the MV-model classical Gaussian effective action as well as solutions of the JIMWLK high-energy renormalization group equation with fixed and running coupling. The initial fields exhibit domain-like structure over distance scales of the order of the saturation scale. At later times universal scaling emerges at large distances for all ensembles, with a nontrivial critical exponent. A similar behavior has earlier been seen in calculations of the gluon transverse momentum spectrum, which becomes independent of the initial spectrum of gauge fields (i.e. the initial unintegrated gluon distribution) for momenta less than the saturation scale. Finally, we compare the results for the Wilson loop to the two-point correlator of magnetic fields.

Speaker: Tuomas Lappi (University of Jyvaskyla)

Slides lappi_qm14.pdf

15:40 Gluon transport equation in the small-angle approximation and the onset of Bose-Einstein condensation

To understand the evolution of a dense system of gluons, such as those produced in the early stages of ultra-relativistic heavy ion collisions, is an important and challenging problem. We describe the approach to thermal equilibrium using the small angle approximation for gluon scattering in a Boltzmann equation that includes the effects of Bose statistics. The role of Bose statistical factors in amplifying the rapid growth of the population of the soft modes is essential. With these factors properly taken into account, one finds that elastic scattering alone provides an efficient mechanism for populating soft modes, and in fact leads to rapid infrared local thermalization. Furthermore recent developments suggest that high initial overpopulation plays a key role and may lead to dynamical Bose-Einstein Condensation. The kinetics of condensation is an interesting problem in itself. By solving the transport equation for initial conditions with a large enough initial phase-space density the equilibrium state contains a Bose condensate, and we present numerical evidence that such over-populated systems reach the onset of Bose-Einstein condensation in a finite time. It is also found that the approach to condensation is characterized by a scaling behavior. Finally we discuss a number of extensions of the present study. Reference: Blaizot, Liao, McLerran, Nucl. Phys. A920(2013)58.

Speaker: Jinfeng Liao (Indiana University)

Slides LIAO_BEC_QM14.pdf

14:20 → 16:00 Heavy flavor: 2

Convener: Dmitri Kharzeev (Stony Brook U./BNL)

announcement QM2014_announcement_Wed.pdf

14:20 Elastic and radiative heavy quark energy loss within a transport model

The full space-time evolution of heavy quarks and light partons in ultra-relativistic heavy-ion collisions is studied within the partonic transport model Boltzmann Approach to MultiParton Scatterings (BAMPS). We discuss in detail for all flavors the influence of elastic and radiative energy loss with a running coupling. Radiative processes, in particular, are implemented through an improved version of the Gunion-Bertsch matrix element, which is derived from comparisons to the exact result. In this calculation the finite heavy quark masses are explicitly taken into account, leading to the dead cone effect. Consequently, we present results of this updated version of BAMPS and compare them to experimental data at RHIC and LHC. In detail, the nuclear modification factor and elliptic flow of charged hadrons, heavy flavor electrons as well as muons, D mesons, and non-prompt J/psi are discussed. The latter two are especially sensitive to the mass difference of charm and bottom quarks. Furthermore, we make predictions where no data is available yet.

Speaker: Jan Uphoff (Goethe University Frankfurt)

Slides jan_uphoff_qm14.pdf

14:40 AdS/CFT heavy-quark energy loss beyond the leading order

We present new predictions for the suppression of heavy quark decay products at RHIC and LHC from a NLO AdS/CFT energy loss model. Previous predictions from a tomographic model based on only the leading order AdS/CFT contribution to energy loss and constrained by RHIC data disagreed with LHC D meson measurements. In this work we include for the first time a correct treatment of the momentum fluctuations induced in the heavy quark motion from the strongly-coupled thermal medium: we resolve the ambiguity in the evaluation of the stochastic Langevin equations using the Wong-Zakai theorem and properly take into account the fluctuations' deviations from the Einstein relations. The addition of the fluctuations leads to corrections to the suppression predictions, which are significant for charm quarks and their decay products. We demonstrate how further experimental measurements can provide insight into the dominant energy loss mechanisms in, and hence the physical properties of, the quark-gluon plasma produced in heavy ion collisions.

Speaker: William Horowitz (University of Cape Town)

Slides 140517(QM)Horowitz.pdf 140517(QM)Horowitz.pptx

15:00 Measurements of the heavy-flavour nuclear modification factor in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the LHC

The LHC heavy-ion physics program aims at investigating the properties of strongly interacting matter at extreme conditions of temperature and energy density, where the formation of the Quark-Gluon Plasma (QGP) is expected. In high-energy heavy-ion collisions, heavy quarks are regarded as effective probes of the properties of the QGP as they are created on a short time scale, with respect to that of the QGP, and subsequently interact with it. The nuclear modification factor $R_{\rm AA}$, defined as the ratio of the yield measured in Pb-Pb to that observed in pp collisions scaled with the number of binary nucleon-nucleon collisions, is used to study the mechanisms of heavy quark in-medium energy loss and hadronization. In order to disantangle hot and cold nuclear matter effects, the nuclear modification factor was measured in p-Pb collisions where the formation of a large volume hot and dense medium is not expected. Heavy-flavour production in p-Pb collisions has also its own interest since it allows us to investigate initial state effects such as modifications of the parton distribution functions in the nucleus, gluon saturation and $k_{\rm T}$ broadening. With ALICE, the detector designed and optimized for heavy-ion physics at the LHC, open heavy flavours are measured at central rapidity using using their hadronic and semi-electronic decays as well as at forward and backward rapidity using their semi-muonic decays. The latest results on the nuclear modification factor of charmed mesons and electrons and muons from heavy-flavour hadron decays in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented. Comparisons with theoretical predictions will be discussed.

Speaker: Shuang Li (Univ. Blaise Pascal Clermont-Fe. II (FR))

Slides QM_ShuangLi_v8.pdf

15:20 Heavy-flavour production as a function of multiplicity in pp and p-Pb collisions

The measurement of heavy-flavour production cross sections in pp collisions at the LHC provides a reference for heavy-ion studies and represents a test for perturbative QCD calculations. In p-Pb collisions, heavy-flavour measurements are essential to assess the effects due to the presence of a nucleus in the initial state, such as the modification of the parton densities and the $k_{\rm T}$-broadening resulting from multiple soft scatterings of the partons. Heavy-flavour measurements as a function of the multiplicity of charged particles produced in the collision are sensitive to the interplay between hard and soft contributions to particle production and, in particular, could give insight into the role of multi-parton interactions (MPI), i.e. several hard partonic interactions occuring in a single collision at high centre-of-mass energies. In this talk we will focus on the measurement of open heavy-flavour production as a function of charged-particle multiplicity in pp collisions at $\sqrt {s}$ = 7 TeV and p-Pb collisions at $\sqrt {s_{\rm NN}}$=5.02 TeV recorded with the ALICE detector in 2010 and 2013, respectively. D$^{0}$, D$^{+}$ and D$^{*+}$ are reconstructed from their hadronic decay modes in the central rapidity region, and their yields are measured in different multiplicity and $p_{\rm T}$ intervals. The per-event yield of D mesons in the different multiplicity intervals, normalized to its multiplicity-integrated value, and its evolution with $p_{\rm T}$ will be compared for pp and p-Pb collisions to study the contribution of MPI to open charm production in the two systems. The nuclear modification factor of D mesons in p-Pb collisions, defined as the ratio of the D-meson yield in p-Pb and pp collisions scaled by the number of binary collisions $N_{\rm coll}$, will be discussed in terms of its multiplicity dependence. Results obtained with different multiplicity estimators will be shown in order to better understand the connection between multiplicity and collision geometry, which is needed to determine $N_{\rm coll}$.

Speaker: Riccardo Russo (Universita e INFN (IT))

Slides RussoQM2014.pdf

15:40 Open beauty measurements in pPb collisions with CMS

We report the first measurements of fully reconstructed B mesons in collisions involving heavy ions. Rapidity and transverse momentum cross sections, measured at $\sqrt{s_{NN}}=5.02$ TeV with the CMS detector, will be presented. For the same collision system, we will also report on the production of inclusive $b$-hadrons identified via their decays into $J/\psi$ displaced from the primary collision vertex, and measured in a similar kinematic range as the identified B mesons. The nuclear modification factors, which are constructed using a theoretically calculated pp reference, will be shown together with cross-section asymmetries between equivalent positive and negative pseudo-rapidity ranges in the center-of-mass frame of the collision.

Speaker: Hyunchul Kim (Korea University (KR))

Slides HyunchulKim_QM2014_FINAL.pdf

16:05 → 16:30 Coffee break

16:30 → 18:30 Collective dynamics: 3

Convener: Barbara Erazmus (CNRS/IN2P3)

announcement announcement-tuesday.pdf

16:30 Searches for azimuthal flow in pp, p-Pb and Pb-Pb collisions from ALICE

A key question facing the heavy-ion physics community is whether or not collective behavior develops in elementary collisions. We will utilize a variety of techniques designed to obtain elliptic and triangular flow coefficients ($v_{2}$ and $v_{3}$) on data from pp $\sqrt{s} = 7$ TeV and p-Pb $\sqrt{s_{\rm NN}} = 5.02$ TeV collisions. We will report new measurements of second, fourth, and sixth particle flow cumulants for charged hadrons in p-Pb collisions as a function of charged hadron multiplicity, and discuss their response to few and global azimuthal correlations. New results will also be shown for Pb-Pb $\sqrt{s_{\rm NN}} = 2.76$ TeV, as they provide a crucial reference for such studies. Finally, we will report new measurements of $v_{2}\{SP\}$ for charged hadrons and identified particles for pp and p-Pb collisions. Investigations into mass ordering and comparisons to measurements of $v_{2}\{SP\}$ from Pb-Pb collisions will be carried out.

Speaker: Anthony Robert Timmins (University of Houston (US))

Slides QM2014TimminsV4.pdf QM2014TimminsV4.pptx

16:50 A scaling relation between proton-nucleus and nucleus-nucleus collisions

I compare the flow-like correlations in high multiplicity proton-nucleus (p + A) and nucleus- nucleus (A + A) collisions. At fixed multiplicity, the correlations in these two colliding systems are strikingly similar, although though the system size in p + A is smaller. Based on an independent cluster model and a simple conformal scaling argument, where the ratio of the mean free path to the system size stays constant at fixed multiplicity, I argue that flow in p + A emerges as a collective response to the fluctuations in the position of the clusters, just like in A + A collisions. By examining the recent LHC data carefully, I show that this simple model captures the essential physics of elliptic and triangular flow in p + A collisions. I also explore the implications of the model for jet energy loss in p + A collisions.

Speaker: Dr Gokce Basar (Stony Brook University)

Slides pA_QM2.pdf

17:10 Flow in Cu+Au collisions and unique tests of 3D medium evolution

Cu$+$Au collisions at RHIC have provided the first asymmetric heavy-ion collisions at collider energies, where it is generally believed that nuclear matter above the Quark-Gluon Plasma (QGP) transition is created. The Cu$+$Au system provides a unique arena for QGP production and development with novel features that are inaccessible in symmetric A$+$A collisions, such as intrinsic transverse triangularity at mid-centrality and a completely occluded, corona-less smaller nucleus in the most central collisions. Further, because the participant nucleon groups from the two nuclei are distinguishably different it may be possible to trace the sources of initial deposition of such conserved quantities as energy and transverse momentum in 3D across the medium. In this talk we present new PHENIX results on flow observables from Cu$+$Au collisions across both $p_T$ and (pseudo)rapidity, and discuss how they can be used to diagnose the full three-dimensional formation and evolution of the QGP fluid.

Speaker: Hiroshi Nakagomi (Tsukuba University)

Slides QM14_Hiroshi_CuAu_v6.pdf

17:30 Elliptic flow and nuclear modification factor within a partonic transport model

An updated version of the partonic transport model Boltzmann Approach to Multi-Parton Scatterings (BAMPS) is presented, which numerically solves the 3+1D Boltzmann equation by allowing interactions among all parton species: gluons, light quarks, and heavy quarks with both elastic and inelastic collisions. We introduce the improved Gunion-Bertsch matrix element, which cures problems of the original Gunion-Bertsch result in characteristic regions of the phase space. Based on extensive numerical calculations, the improved matrix element agrees well with the exact pQCD calculation. While employing the new matrix element, important properties of the quark-gluon plasma created in heavy-ion collisions such as the thermalization time of the plasma and the shear viscosity over entropy density ratio are calculated within the microscopic transport model BAMPS. Furthermore, we compare our results of the nuclear modification factor and elliptic flow to experimental data measured at RHIC and LHC.

Speaker: Florian Senzel (Goethe-Universität Frankfurt)

Slides QM2014_Senzel_V2.pdf

17:50 Exploiting intrinsic triangular geometry in relativistic He3+Au collisions to disentangle medium properties

Recent results in d+Au and p+Pb collisions at RHIC and the LHC provide evidence for collective expansion and flow of the created medium. We propose a control set of experiments to directly compare particle emission patterns from p+Au, d+Au, and He3+Au or t+Au collisions at the same sqrt(sNN). Using Monte Carlo Glauber we find that a He3 or triton projectile, with a realistic wavefunction description, induces a significant intrinsic triangular shape to the initial medium and that, even with viscous damping, this survives into a significant third order flow moment v3. By comparing systems with one, two, and three initial hot spots, one can disentangle the effects from the initial spatial distribution of the deposited energy and viscous damping. These are key tools to answering the question of how small a droplet of matter is necessary to form a quark-gluon plasma described by nearly inviscid hydrodynamics. We describe our results from (arXiv:1312.4565) as well as new calculations including coupling to a hadronic cascade afterburner and full particle identified flow patterns.

Speaker: Paul Romatschke (U)

Slides Romatschke_QM14.pdf Romatschke_QM14.pptx

18:10 Will perfect fluidity of the sQGP survive in light of the BES & D+Au & p+Au data?

Recent low pT<2 GeV vn data on the beam energy scan (BES) and D+Au at RHIC and the surprising data on low pT vn in p+Pb at LHC challenge long held assumptions about the validity or necessity of perfect fluid hydrodynamics in A+A. Could classical field interference phenomena from color antenna arrays and or Unruh noninertial color currents play a critical role in resolving the BES+DA+pA puzzle? We explore non-hydrodynamic scenarios that could generate apparent collective flow signatures in vn observables.

Speaker: Prof. Miklos Gyulassy (Columbia University)

Slides Gyulassy-QM14-vf.2.pdf Gyulassy-QM14-vf.pdf

16:30 → 18:30 Electromagnetic probes: 3

Convener: Joachim Stroth (Goethe-University and GSI)

slides QM2014_announcement_reception_football.pdf

16:30 Measurements of direct-photon-hadron correlations and direct-photon azimuthal anisotropy by STAR

Many observations have indicated that the fragmentation functions in nucleus-nucleus collisions are softened compared to that in proton-proton collisions. Different theoretical models have been proposed in order to describe the observed phenomena. For a deeper insight into the underlying physics and better constraints for the extracted parameters of the medium formed in nucleus-nucleus collisions, a calibrated probe is needed. Direct photons act as such probes, providing experimental tools to explore energy loss of hard-scattered patrons. We report systematic studies of azimuthal correlations of charged hadrons with respect to a direct-photon trigger in p+p and Au+Au collisions, using new data collected in 2008, 2009, and 2011. The nuclear modification factor of coincidence rate, $I_{AA}$, will be shown. We also report direct-photon azimuthal anisotropy as a function of transverse momentum at mid-rapidity with event plane reconstructed from particles at forward rapidity in Au+Au collisions using the STAR detector at RHIC. We discuss the results in the scope of current theoretical models.

Speaker: Dr Ahmed M. Hamed (University of Mississippi, Texas A&M University)

Slides Direct_photon_QM-2014_Final.pdf Direct_photon_QM-2014_Final.pptx

16:50 Soft photon production from real-time dynamics of jet fragmentation

Soft photons produced in heavy ion collisions are an important tool in probing the properties of the quark-gluon plasma. For this purpose, it is crucial to understand the background - soft photons produced in elementary collisions. Low theorem states that soft photon production in hadron collisions is dominated by Bremsstrahlung off charged initial and final state hadrons. Surprisingly, almost every experiment observed an enhancement (by a factor of $2\div 5$) above Low theorem's prediction. This is the longstanding puzzle of "anomalous soft photon production." The phenomenon is not observed in processes with leptonic final states, which suggests that the mechanism is due to nonperturbative QCD evolution. We study this phenomenon using an exactly soluble, massless, Abelian model in $1+1$ dimensions which shares with QCD many important properties: confinement, chiral symmetry breaking, axial anomaly and $\theta$-vacuum. We then apply this model to the soft photon production in the fragmentation of jets produced in $Z^0$ decays and find a qualitative agreement with the data.

Speaker: Frasher Loshaj (Stony Brook University)

Slides QM2014_talk.pdf

17:10 Z and W production in pp, pPb and PbPb collisions with CMS

The weak bosons, Z and W, do not participate in the strong interaction, and thus constitute clean probes of the initial state of nuclear collisions. Detected trough their leptonic decay channels, they provide constraints on the nuclear parton distribution functions (PDF). In particular the W boson proves a unique constraint on the sea quark distributions. We report on CMS measurements of weak boson production in pp, pPb and PbPb. Particular emphasis is place on measurements of the 35 nb$^{-1}$ of pPb data collected at the beginning of 2013. This provides access to a Bjorken x region, $10^{-3}$ -- 1, which is lacking precision experimental measurements needed by nuclear PDF parametrizations. The Z boson nuclear modification factors as a function of transverse momentum and rapidity will be shown, together with forward to backward ratios. The W boson yields, charge asymmetries, and forward to backward ratios in pPb collisions will also be reported. With a production cross section an order of magnitude larger than the Z, the W allows precise comparisons to theoretical predictions. Comparisons to PDFs are made for both Z and W measurements

Speaker: Anna Zsigmond (Wigner RCP, Budapest (HU))

Slides QM2014_AZsigmond_v3.pdf

17:30 Measurements of vector boson production in lead-lead and proton-lead collisions with the ATLAS detector

Photons and weak bosons do not interact strongly, and thus their production yields provide direct tests of binary collision scaling, and in addition should be sensitive to the nuclear modification of parton distribution functions (nPDFs). Proton-lead collisions also provide an excellent opportunity to test nPDFs in a less dense environment than lead-lead, along with useful forward backward asymmetries in the final state.   The ATLAS detector has proven to be an excellent apparatus in measurements involving photons, electrons and muons, the latter being products of weak-boson decays, in the high occupancy environment produced in heavy ion collisions. The experiment has recorded 30 $nb^{-1}$ of proton-lead data and 140 $\mu b^{-1}$ of lead-lead data, both of which have similar integrated partonic luminosities.  We will present the prompt photon, Z and W boson yields as a function of centrality, and also differentially in transverse momentum and rapidity, in lead-lead and proton-lead collisions from the ATLAS experiment. For W bosons also a lepton charge asymmetry has been studied, which may also shed light on nPDFs.

Speaker: Iwona Grabowska-Bold (AGH University of Science and Technology (PL))

Slides QM14-AtlasVectorBosons-19052014.pdf

17:50 The QCD phase diagram in the region of moderate temperature and high baryon density: study of dimuon production in the 20-160 AGeV interval at the CERN SPS

The structure of the QCD phase diagram in the region of moderate temperature and high baryon density is still almost unexplored. In this regime, the QGP and hadronic phases should be separated by a first order transition region. On the other hand, for sufficiently low baryonic chemical potential a simple cross-over is expected. The end point of the first order transition region is the so called critical point. Measurements of the ratio $K^+/\pi^+$ vs energy performed at the CERN SPS by the NA49 collaboration showed that the early stage produced in central Pb-Pb collisions at $E_{lab}$=30-40 AGeV may have reached the transition line - marking the onset of deconfinement. However, this interpretation is still controversial. Dilepton measurements with a rich set of independent observables offer a completely independent way to shed light on the onset of deconfinement and at the same time on the issue of chiral restoration. The CERN SPS is unique for systematic investigations along these lines, due to its wide beam energy range from 20-160 AGeV coupled to very high luminosities over the full range. The objective of this talk is to present a new proposal for measuring dimuon production in a comprehensive energy scan at the SPS - specifically both below and above the maximum of the $K^+/\pi^+$ ratio. To advance the field with measurements which could provide quantitative insight, a further significant increase in the precision and in the collected statistics with respect to the past reference experiment NA60 is needed. To this end, we propose a novel NA60-like apparatus, with improved performance, based on the coupling of a muon spectrometer to a a silicon pixel spectrometer in the vertex region before the absorber. The first key element is a high-precision measurement of the temperature $T$ of the thermal dimuon continuum in the mass range $1.1\lt M\lt2.5$ GeV (IMR) vs. beam energy. The temperature is accessible through the spectral shape of the mass spectra, and since mass is a Lorentz-invariant, $T$ is immune to any motion of the emitting sources and thus purely thermal, in contrast to the slope parameters of dilepton $m_T$ spectra or photon $p_T$ spectra. At top SPS energies, values of about 200 MeV were found, indicating dominantly partonic emission sources. For decreasing beam energies one should expect that the partonic contribution will also decrease, becoming negligible at the onset of deconfinement. Thus the onset of deconfinement might be tagged by a precision measurement of $T$ in the IMR. The second element is related to the transverse momentum spectra, which encode - besides temperature - also radial flow, another key property of the fireball. At topmost SPS energies the effective temperature extracted from the $m_T$ spectra vs mass shows an increase up to $M\sim1$ GeV corresponding to $\rho$ production which is maximally coupled to radial flow through pions. At 1 GeV a sudden drop occurs and the temperature is constant at 180-200 MeV - a sign of production of thermal dimuons from the partonic medium without any flow (at the SPS). The evolution of the pattern of $T_{eff}$ vs. $M$ towards lower energies, in particular the possible decrease or disappearence of the drop, will be most revealing: thermal radiation from multi-pion processes should exhibit a monotonic increase of $T_{eff}$ vs $M$ so that around the onset of deconfinement the drop should vanish. The new experiment should reach a sensitivity at the MeV level in the measurements of $T$ and $T_{eff}$ vs $M$. This will be possible integrating luminosities at least an order of magnitude larger than in case of NA60 or so while retaining a good signal to background ratio - well above than 1/100 in the IMR even in Pb-Pb central collisions. For masses below 1 GeV (LMR), at high energies, hadronic many body models describe $\rho$ production and the notion that the total baryon density drives the broadening is now well accepted. At lower energies, the baryon density gets maximal, thus the effects of $\rho$ broadening can be measured with utmost precision. In this measurement the mass resolution is a key factor and we propose to improve it over NA60 by a factor 2-3, reaching $\sim$10 MeV at the $\omega$ mass. The experimental apparatus must have also a good $p_T$-$y$ coverage down to the lowest beam energies. In the talk the detector perfomance in terms of acceptances at different energies and mass resolution will be discussed in detail. The physics performance will be presented on the basis of simulations of Pb-Pb collisions at 20 and 40 AGeV including a background estimate and a modeling of the involved physics processes - in medium $\rho$ in the LMR, multi-pion processes and partonic radiation in the IMR. An overview of the possible detector technologies together with a cost estimate will be also presented. Finally, an experimental program consisting of measurements at different energies and/or different collision systems will be discussed in terms of beam time needed to collect the required event statistics.

Speaker: Gianluca Usai (Universita e INFN (IT))

Slides QM2014-usai-final.pdf

18:10 Measurements of dileptons with the CBM-Experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment at the upcoming Facility for Antiproton and Ion Research (FAIR) will explore the phase diagram of nuclear matter at very high net-baryon densities and moderate temperatures in nucleus-nucleus collisions at beam energies up to 45 A GeV . One of the key diagnostic probes of strongly-interacting matter at extreme conditions are dileptons. Dilepton measurements performed so far in heavy-ion collisions at various energies have found that the major challenge is to subtract the combinatorial background which overwhelms the interesting signals such as the rho spectral distribution, direct radiation from the fireball at intermediate invariant masses, and charmonia. This background is of different physical origin for dielectron and dimuons, and differs as function of invariant mass. Therefore, the systematic and statistical errors of the extracted signals will be substantially minimized by measuring both electron and muon pairs. The CBM detector is designed as a multi-purpose device which will be able to measure hadrons, electrons and muons in heavy-ion collisions. Electrons will be measured using a Ring Imaging Cherenkov (RICH) detector in combination with a Transition Radiation Detector. For muon measurements, the RICH detector will be replaced by a large area Muon detection system consisting of alternating layers of hadron absorbers and tracking chambers. The results of performance studies and the status of the detector developments will be presented.

Speaker: Claudia Hoehne (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

Slides CBM_Dileptons_QM2014_Hoehne.pdf CBM_Dileptons_QM2014_Hoehne.ppt

16:30 → 18:30 Initial state physics: 2

Convener: Kari J. Eskola (University of Jyvaskyla)

slides QM2014_announcement_reception_football.pdf

16:30 Production of light flavor hadrons at intermediate and high $p_{\rm T}$ measured with the ALICE detector

Light flavor transverse momentum spectra at intermediate and high $p_{\rm T}$ are important as baseline perturbative QCD measurements in pp, evaluating initial state effects (nuclear p.d.f.'s) in p-Pb, and for investigating the suppression in Pb-Pb collisions. In this talk results for all these collisional systems will be presented. The new measurement of $R_{\rm pPb}$ for unidentified charged particles extended up to 50 GeV/$c$ will be presented together with the construction of the reference pp spectrum at $\sqrt{s} = 5.02$ TeV. The final results on the production of charged pions, kaons, and protons up to $p_{\rm T} = 20$ GeV/$c$ in pp and Pb-Pb collisions will also be reported and compared to recent QCD and phenomenological calculations. The impact of these results on our interpretation of jet quenching in Pb-Pb through $R_{\rm AA}$ and the question of whether the proton-to-pion ratio can still be considered to be anomalous will be discussed.

Speaker: Michael Linus Knichel (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

Slides MKNICHEL_HIGHPTHADRONS_QM2014.pdf

16:50 Centrality dependence of particle production in p-A collisions measured by ALICE

Measurements of particle production in proton-nucleus collisions provide a reference to disentangle final state effects, i.e. signatures of the formation of a deconfined hot medium, from initial state effects, already present in cold nuclear matter. While most of the benchmarks from the control experiment indicate that initial state effects do not play a role in the observed suppression of hadron production observed in heavy ion collisions, several measurements of particle production in the low and intermediate $p_{\rm T}$ region indicate the presence of collective effects. Since many initial state effects are expected to vary as a function of the number of collisions suffered by the incoming projectile, it is crucial to estimate event-by-event the centrality of the collision. We present the centrality dependence of particle production in p-A collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV measured by the ALICE experiment, including the pseudo-rapidity and transverse momentum spectra, with a special emphasis on the event classification in centrality classes and its implications in the interpretation of the nuclear effects.

Speaker: Dr Alberica Toia (Johann-Wolfgang-Goethe Univ. (DE))

Slides AlbericaToia_QM2014.pdf

17:10 Decoherence between the initial and final state radiation in a dense QCD medium

We study medium modifications to the interference pattern between initial and final state radiation. We compute single gluon production off a highly energetic parton that undergoes a hard scattering and subsequently crosses a dense QCD medium of finite size. Multiple soft scatterings with the medium are resumed within the harmonic oscillator approximation. We find the decoherence of correlated partons traversing the medium depends on two scales: the medium length $L$ and the decorrelation time of the gluon due to the medium $\tau_f$. This interplay gives origin to two different asymptotic limits of the gluon spectrum: the coherent ($\tau_f\gg L$) and incoherent regime ($\tau_f\ll L$). We discuss the main characteristics of each regime. We show that in both cases there is a gradual onset of decoherence between the initial and final state radiation due to multiple scatterings, that opens the phase space for large angle emissions. By examining the multiplicity of produced gluons, we observe a potentially large double logarithmic enhancement for dense media and small opening angles. This result points to a possible modification of the evolution equations due to a QCD medium of finite size. We comment on the phenomenological consequences (such as radiative energy loss) of this setup in pA collisions.

Speaker: Mauricio Martinez Guerrero (The Ohio State University)

Slides QM2014.pdf

17:30 Searching for the "Ridge" in d+Au collisions at RHIC by STAR

Long-range pseudo-rapidity ($\Delta\eta$) correlations at small azimuthal difference ($\Delta\phi$) are observed in high multiplicity p+p and p+Pb collisions at the LHC. Subtraction of the di-hadron correlation in low-multiplicity p+Pb collisions from high-multiplicity ones reveals a back-to-back double ridge structure ($\Delta\phi\approx 0$ and $\pi$). A similar double ridge is observed in high-multiplicity d+Au collisions by the PHENIX experiment in their limited acceptance. Differences between multiplicity-selected d+Au collisions (and p+p collisions) have been observed before by STAR. However, the question remains open whether the ridge in d+Au collisions is a jet-related difference between central and peripheral collisions, or a new physics phenomenon such as anisotropic flow in d+Au. STAR, with its large acceptance, can rigorously address this question. In this talk, we report di-hadron $\Delta\eta$-$\Delta\phi$ correlations in d+Au collisions at $\sqrt{s_{NN}} =$ 200 GeV. At mid-rapidity (with $|\Delta\eta|<2$), the jet-like correlation contribution in ``central$-$peripheral" method is evaluated. At large $|\Delta\eta|\approx 3$, the comparison of di-hadron correlations in central and peripheral collisions is reported in terms of the Au and deuteron beam directions. The $\Delta\phi$ correlation functions are also analyzed via a Fourier series decomposition; the $|\Delta\eta|$ and multiplicity dependencies of the Fourier coefficients are investigated. These di-hadron correlations data over the large acceptance may elucidate the existence or lack of a ridge in d+Au collisions at RHIC.

Speaker: Li Yi

Slides dAuRidge_QM14_LiYi_v11.pdf

17:50 A unified picture of parton multiple scattering in the small-x regime and forward physics at RHIC and the LHC

The quest for experimental signatures of small-x gluon saturation has been one of the major goals in p+A (d+A) programs at RHIC and LHC. Experimental measurements of single particle and two-particle correlations in the forward direction have revealed novel nuclear suppression patterns, which might help pinpoint the small-x gluon dynamics. At the moment there are two formalisms which can both describe reasonably well the nuclear suppression observed in these experiments. One is the so-called higher-twist factorization approach, which describes the parton multiple scattering in terms of the power corrections to the differential cross section [1,2]. The other one is the so-called small-x color glass condensate (CGC) approach [3]. So far the precise connection between these two approaches has not been established. In this talk, we demonstrate how the multiple parton scattering picture and the small-x gluon saturation picture are related and show how the transition from a dilute parton system to a dense gluon saturation region occurs. Our work unifies the two approaches in studying the nonlinear small-x parton dynamics. On the example of forward rapidity photon production in p+A collisions, we demonstrate that in the broad transition region between a dilute parton system and a deeply saturated regime the two approaches give identical results. This work also helps understand the constraints on the small-x phenomenological studies. [1] J. Qiu and I. Vitev, Phys. Lett. B632, 507 (2006) [2] Z. B. Kang, I. Vitev and H. Xing, Phys. Rev. D85, 054024 (2012) [3] see, e.g., J. L. Albacete and C. Marquet, Phys. Rev. Lett. 105, 162301 (2010)

Speaker: Zhongbo Kang (L)

Slides QM2014_Chien.pdf

18:10 Dijets in p+Pb collisions and their quantitative constraints for nuclear PDFs

We present a perturbative QCD analysis concerning the production of high-pT dijets in p+Pb collisions at the LHC. The next-to-leading order corrections, scale variations and free-proton PDF uncertainties are found to have only a relatively small influence on the normalized dijet rapidity distributions. Interestingly, however, these novel observables prove to retain substantial sensitivity to the nuclear effects in the PDFs. Especially, they serve as a more robust probe of the nuclear gluon densities at x > 0.01, than e.g. the inclusive hadron production. We confront our calculations with the recent data by the CMS collaboration. These preliminary data lend striking support to the gluon antishadowing similar to that in the EPS09 nuclear PDFs.

Speaker: Dr Hannu Paukkunen (University of Jyväskylä)

Slides QM2014_Paukkunen.pdf

16:30 → 18:30 Heavy flavor: 3

Convener: Federico Antinori (Universita e INFN (IT))

announcement QM2014_announcement_Wed.pdf

16:30 Heavy-flavour correlations in pp, p-Pb and Pb-Pb collisions

Heavy quarks (charm and beauty) are excellent probes to study the properties of the strongly interacting matter formed in heavy ion collisions, which is expected to be a Quark-Gluon Plasma (QGP). Indeed, due to their large mass, charm and beauty quarks are produced in initial hard scattering processes among partons of the colliding nuclei, before the formation of the QGP, and they traverse the medium and interact with its constituents. The ALICE Collaboration measured the production of open heavy-flavour hadrons via their hadronic and semi-leptonic decays at mid-rapidity in pp, p-Pb and Pb-Pb collisions at $\sqrt{s_{NN}}$ = 7, 5.02 and 2.76 TeV respectively. A strong suppression of the open charm hadron yields at high $p_{\rm T}$ was observed in Pb-Pb collisions relative to pp interactions: this effect is attributed to a substantial in-medium energy loss of the charm quarks. Further insight into the effects of the medium on charm and beauty quarks can be obtained by measuring the angular correlations between open heavy-flavour hadrons and charged hadrons. The comparison of the correlation function in pp and Pb-Pb collisions can provide deeper information on the way heavy quarks lose energy in the QGP and can spot possible modifications to the charm parton shower and hadronisation in the presence of the medium. Furthermore, by studying the correlations of electrons from heavy-flavour decays and the charged hadrons in pp, it is possible to statistically separate the charm and beauty contributions to the yield of heavy-flavour decay electrons, making this analysis an excellent tool to test pQCD calculations. The observation of double-ridge long range correlations in p-Pb collisions for light-flavour hadrons could originate from a collective behaviour of the system, as well as from gluon saturation in the initial state (color glass condensate). The same effect can be studied for heavier quarks via the correlation between heavy-flavour hadrons (or their decay electrons) and charged particles. Results from the correlation analyses, performed using the data collected with ALICE in pp collisions at $\sqrt{s}$ = 7 TeV, Pb-Pb at $\sqrt{s_{\rm NN}}$ = 2.76 TeV, and in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented in this contribution.

Speaker: Sandro Bjelogrlic (NIKHEF (NL))

Slides ALICE_QM2014_HFCorrelations_SB.pdf

16:50 Heavy-flavor evolution in QGP and hadron gas: suppression, flow and angular de-correlation

Heavy flavor hadrons serve as valuable probes of the transport properties of the quark-gluon plasma (QGP) created in relativistic heavy-ion collisions. We introduce a comprehensive framework that describes their full-time evolution in the QGP matter and the subsequent hadronic phase. The heavy quark energy loss in a de-confined QCD medium is modeled with our improved Langevin approach [1] that simultaneously incorporates quasi-elastic scattering [2,3] and medium-induced gluon radiation [4]. The subsequent transport of heavy mesons in the hadron gas phase is described within the ultra-relativistic quantum molecular dynamics (UrQMD) model [5]. The intermediate hadronization process from heavy quarks to their respective mesonic bound states is calculated with our hybrid fragmentation plus coalescence model [1]. We investigate the relative contribution of each of these ingredients to the final-state spectra of heavy mesons and demonstrate that while quasi-elastic scattering dominates heavy quark energy loss in the QGP at low energies, contributions from gluon radiation at high energies are significant; the coalescence process is found important for heavy meson production at intermediate transverse momenta; and the subsequent hadronic interactions is equally crucial as the free quark evolution inside QGP for the development of heavy flavor suppression and collective flow behaviors that one observes. Within this newly developed framework, we provide a good description of D meson suppression and flow measured at both RHIC and LHC, as well as predictions for the future measurements of B mesons. In addition, a new set of observables – heavy-flavor-tagged angular correlation functions – are explored and found to be potential candidates for distinguishing different energy loss mechanisms of heavy quarks inside a QGP medium [6]. We calculate correlation functions for D-D, D-e, D-hadron, e-hadron, etc., some of which can be compared to the existing preliminary data from LHC experiments. 1. S. Cao, G.-Y. Qin, and S. A. Bass, Phys. Rev. C88, 044907 (2013). 2. G. D. Moore and D. Teaney, Phys. Rev. C71, 064904 (2005). 3. S. Cao and S. A. Bass, Phys. Rev. C84, 064902 (2011). 4. B.-W. Zhang, E. Wang, and X.-N. Wang, Phys. Rev. Lett. 93, 072301 (2004). 5. S. A. Bass, et al., Prog. Part. Nucl. Phys. 41, 255-369 (1998). 6. S. Cao, G.-Y. Qin, S. A. Bass and B. Mueller, J. Phys. Conf. Ser. 446, 012035 (2013).

Speaker: Shanshan Cao (Duke University)

Slides QM2014.ppt

17:10 Correlations and higher-order flow: new heavy-quark observables in relation to the bulk dynamics

The progress made by experimental collaborations in measuring heavy-flavor particles in heavy-ion collisions with unprecedented precision is accompanied by the advancement of theoretical calculations. Our recently developed model, which couples a Monte-Carlo Boltzmann-propagation of heavy quarks to the 3+1d fluid dynamical evolution from fluctuating EPOS initial conditions reproduces well the experimental data for the traditional observables like the nuclear modification factor and the elliptic flow. In this talk we will discuss correlations and higher-order flow harmonics as new heavy-quark observables and demonstrate their potential to reveal properties of the QGP. Our studies show that correlations of heavy-flavor particles are sensitive to the energy loss mechanism. Experimentally feasible correlation observables can thus discriminate between elastic and radiative processes and provide valuable information about the transport coefficients. Higher-order flow harmonics, $v_n$, quantify the degree of thermalization of heavy quarks beyond our current understanding of the built-up of elliptic flow. By selecting special classes of bulk events from the probability distribution of $v_n$ of light-flavor hadrons we discuss systematically how relating the light- and the heavy-flavor sector help us understand the interaction mechanisms and thermalization in the QGP.

Speaker: Dr Marlene Nahrgang

Slides qm2014_nahrgang.pdf

17:30 Gluon radiation by heavy quarks at intermediate energies

It is generally admitted that heavy quarks (c and b) created in the early stage of ultrarelativistic heavy ion collisions through hard processes are among the best probes of the later QGP stage. Perturbative QCD allows for the calculation of the production cross sections (in contradistinction to light quarks) and these cross sections have also been measured. Also the details of the chiral/confinement phase transition are less important than for light quarks because, due to its mass, the momentum of the heavy quark determines the momentum of the open charm hadrons. In addition, the momentum distribution at production and at the transition is very different from that expected if the heavy quarks are in thermal equilibrium with the plasma of light quarks and gluons. Therefore the modification of the initial momentum distribution by the interaction of the heavy quarks with the plasma carries information on the plasma properties. The interaction of the heavy quark with the plasma has two parts, elastic collisions and radiative collisions. For the first a model was developed [1] in which the cross section of the elementary interactions are calculated by perturbative QCD with a running coupling constant and an infrared behavior adjusted so as to match hard thermal loop calculations. Embedding these cross sections in the hydrodynamical description of the expanding plasma of Heinz and Kolb it was shown that the collisional energy loss underpredicts the measured energy loss of heavy mesons at large momenta as well as their elliptic flow by roughly a factor of two. It is the purpose of the present work to extend our pQCD calculation toward the calculation of the radiative energy loss for heavy quarks at intermediate energies. To this end we compute the gluon emission cross section of a heavy quark colliding a light parton from the plasma in pQCD at leading order [2]. We first derive the high-energy approximation that naturally extends results obtained by Gunion and Bertsch for the light quark sector to heavy quarks. We next show that it is possible to compute the complete energy dependence of the result. This allows us to assess the range of applicability in energy of the high-energy approximation. We then extend the calculation to the case of intermediate energy, for which the invariant mass $s$ in the collision does not exceed the squared heavy quark mass $m_Q^2$ in large amounts. We discuss in particular the relevance of the dead cone effect as well as the consequences of a finite heavy quark energy, which is often neglected in the literature. For this purpose, we address quantities such as the average energy loss in a bath at finite temperature as well as the nuclear modification factor as a function of the transverse momentum. References ========== [1] P.B. Gossiaux and J. Aichelin, Phys Rev C78, 014904 (2008) [2] J. Aichelin, P.B. Gossiaux and Th. Gousset arXiv:1307.5270, TBP in PRD

Speaker: Pol Gossiaux (Subatech)

Slides QM_2014_gossiaux.pdf

17:50 Energy loss and (de)coherence effects beyond eikonal approximation

The parton branching process is known to be modified in the presence of a medium. Colour decoherence processes are known to determine the process of energy loss when the density of the medium is large enough to break the correlations between partons emitted from the same parent. In order to improve existing calculations that consider eikonal trajectories for both the emitter and the hardest emitted parton, we provide in this work, the calculation of all finite energy corrections for the gluon radiation off a quark in a QCD medium that exist in the small angle approximation and for static scattering centres. Using the path integral formalism, all particles are allowed to undergo Brownian motion in the transverse plane and the offspring allowed to carry an arbitrary fraction of the initial energy. The result is a general expression that contains both coherence and decoherence regimes that are controlled by the density of the medium and by the amount of broadening that each parton acquires independently.

Speaker: Liliana Apolinario (Universidade de Santiago de Compostela (ES))

Slides LilianaQM14.pdf

18:10 Hot and dense quark matter at large number of colors and flavors

I will discuss a holographic model of finite temperature and density QCD matter with a large and roughly equal number of colors and flavours. The basic framework of the model is 5-dimensional classical Einstein gravity with a black hole and with an AdS$_5$ boundary, on which the physical 4-dimensional quantum theory resides. The model further contains a scalar dilaton for asymptotic freedom and confinement, a scalar tachyon for chiral symmetry breaking and a charge density for chemical potential. Solving the classical gravity equations numerically leads to an identification of a chirally symmetric and chirally broken phase with a phase transition in between. The phase transition line on the $T,\mu$ plane can have both 2nd and 1st order segments. The computation can be extended down to the quantum phase transition at $T=0$. The dilaton and tachyon potentials are only constrained by physical properties, not uniquely determined. Until they are derived one cannot make definite predictions, the model rather is a framework for discussing various dynamical alternatives.

Speaker: Prof. Keijo Kajantie (Helsinki Institute of Physics)

Slides qm14.pdf

19:30 → 21:30 Welcome reception

Tuesday 20 May

09:00 → 10:40 Collective dynamics: 4

Convener: Guy Paic (Universidad Nacional Autonoma (MX))

announcement announcement-tuesday.pdf

09:00 Searches for $p_{\rm T}$ dependent flow angle and flow magnitude fluctuations with the ALICE detector

Anisotropic azimuthal correlations are used to probe the properties and the evolution of the system created in heavy-ion collisions. Hydrodynamic model calculations predict that there are effects of $p_{\rm T}$ dependent fluctuations of the flow angle and flow magnitude, which might bias our previous anisotropic flow measurements. In this talk, the two effects will be investigated in both Pb-Pb and p-Pb collisions, using two-particle azimuthal correlation measurements with the ALICE detector. In addition, the factorization of the two-particle Fourier harmonics $V_{n\Delta}$ for different values of $n$ into single-particle azimuthal anisotropies $v_{n}$, will be discussed. Our measurements, together with the comparison to hydrodynamic model calculations will open a new window on the study of the initial state fluctuations and the extraction of shear viscosity of the quark-gluon plasma at the LHC.

Speaker: You Zhou (NIKHEF and University of Utrecht (NL))

Slides YZhou_QM_2014.pdf

09:20 Factorization breakdown of two-particle correlations and flow phenomena in pPb and PbPb collisions with CMS

The technique of two-particle correlations has been widely used in studying flow via azimuthal anisotropy in relativistic heavy-ion collisions. A key assumption imposed in this approach is the factorization of Fourier coefficients extracted from two-particle correlations into a product of single-particle anisotropies of trigger and associated particles. It was recently predicted by hydrodynamics that due to initial-state participant fluctuations, a transverse momentum ($p_T$) dependence of the event-plane angle would be induced, leading to a breakdown of factorization, even if hydrodynamic flow is the only source of correlations. We present a systematic examination of the factorization assumption in 5.02 TeV pPb and 2.76 TeV PbPb collisions with the CMS experiment. Significant breakdown of factorization (up to 20%) is observed in a large sample of ultra-central (0--0.2%) triggered PbPb events, where initial-state fluctuations play a dominant role. Comparison of data and viscous hydrodynamics predictions, as a function of $p_T$ and centrality, allows new constraints on the modeling of initial condition and shear viscosity to entropy density ($\eta/s$) ratio of the medium created in heavy-ion collisions. Furthermore, the measurement is also extended to high-multiplicity pPb collisions. As the initial-state geometry of a pPb collision is expected to be entirely a consequence of fluctuations, quantitative studies of factorization breakdown will help to investigate the nature of the observed long-range correlations in pPb collisions, particularly in the context of hydrodynamic models.

Speaker: Damir Devetak (University of Belgrade (RS))

Slides QM_damir_devetak_final.pdf

09:40 Elucidating the event-shape fluctuations via flow correlations and jet tomography studies in 2.76 TeV Pb+Pb collisions using the ATLAS detector

Measurements of the distributions of event-by-event flow harmonics $v_n$ and the correlations between harmonics $v_n$ and $v_m$ of different orders in $\sqrt{s_{NN}}=2.76$ TeV Pb+Pb collisions are presented. These measurements give insight into the nature of fluctuations in the initial geometry and the role of linear and non-linear hydrodynamic response to the fluctuations, the latter can introduce correlations between flow harmonics. The study of fluctuations is also extended by measurements of the rapidity dependent fluctuations in the v_n. Furthermore, the event-by-event fluctuations in the event shape is elucidated by jet-tomography studies, where the correlations between the $v_n$ of fully reconstructed jets and the $v_m$ of soft particles are measured. The latter directly probes the path-length dependent jet quenching response to the variation of the event-shape controlled by bulk particles.

Speaker: Soumya Mohapatra (State University of New York (US))

Slides QM.pdf QM.pptx

10:00 A perturbative approach to hydrodynamics

Initial fluctuations in hydrodynamic fields such as energy density or flow velocity give access to understanding initial state and equilibration physics as well as thermodynamic and transport properties. We provide evidence that the fluid dynamic propagation of fluctuations of realistic size can be based on a background-fluctuation splitting and a systematic perturbative expansion in the fluctuating fields. Initial conditions are characterized by a Bessel-Fourier expansion for single events, event-by-event correlations and probability distributions. The evolution equations can be solved order-by-order in the expansion which allows to study the fluid dynamical propagation of single modes, the study of interaction effects between modes, the determination of the associated particle spectra and the generalization of the whole program to event-by-event correlations and distributions. We also show comparisons to flow measurements at the LHC.

Speaker: Stefan Floerchinger (CERN)

Slides FloerchingerQM2014.pdf

10:20 Heavy ions collision evolution modeling with ECHO-QGP

We present a numerical code for modeling relativistic heavy ion collisions, ECHO-QGP. The code includes relativistic hydrodynamics with dissipative terms and implements Israel-Stewart theory in 3+1 D. Initial conditions are provided through an implementation of the Glauber model (both Optical and Monte Carlo), while freezeout and particle generation is based on the Cooper-Frye prescription. ECHO-QGP features dynamical metric tensor in a GR framework for ideal hydro and it can work in Bjorken and cartesian frames for the dissipative case. The code shows remarkable stability and accuracy with the combination of a conservative (shock-capturing) approach with the high-order methods. ECHO-QGP is able to reproduce several known solutions of ideal and dissipative hydrodynamics including the lately proposed Gubser test. Ref. L. Del Zanna, V. Chandra, G. Inghirami, V. Rolando, A. Beraudo, A. De Pace, G. Pagliara, A. Drago and F. Becattini, *"Relativistic viscous hydrodynamics for heavy-ion collisions with ECHO-QGP"* Eur. Phys. J. C **73**, 2524 (2013)

Speaker: Ms Valentina Rolando (Università di Ferrara, INFN Ferrara)

Slides QM2014_rolando.pdf QM2014_rolando_wbackup.pdf

09:00 → 10:40 QCD phase diagram: 1

Convener: Tetsuo Hatsuda (Unknown)

announcement QM2014_announcement_Wed.pdf

09:00 Probing dense matter in compact star cores with radio pulsar data

Astrophysical observations of compact stars provide, in addition to collider experiments, the other big source of information on matter under extreme conditions. The largest and most precise data set about neutron stars is the timing data of radio pulsars. We show how this unique data can be used to learn about the ultra-dense matter in the compact star interior. The method relies on astro-seismology based on special global oscillation modes (r-modes) that emit gravitational waves. They would prevent pulsars from spinning with their observed high frequencies, unless the damping of these modes, determined by the microscopic properties of matter, can prevent this. We show that for each form of matter there is a distinct region in a frequency/spindown-rate diagram where r-modes can be present. We find that stars containing quark matter are consistent with both the observed radio and x-ray data, whereas for standard neutron stars so far unestablished, enhanced damping mechanisms would be required.

Speaker: Kai Schwenzer (W)

Slides Probing_quark_matter.pdf

09:20 $\Lambda$($K_{S}^{0}$)-$h^{\pm}$ azimuthal correlations with respect to event plane and searches for chiral magnetic and vortical effects

QCD allows for the formation of parity-odd domains inside the Quark-Gluon Plasma (QGP). The proposed Chiral Magnetic Effect (CME) will lead to charge separation with respect to the reaction plane. Previous measurements from RHIC and LHC using charge-dependent two-particle azimuthal correlations with respect to the reaction plane are consistent with the expectation of charge separation from CME. However, the magnitude of the background correlation has not been understood and there is no reliable experimental approach to separate the background from a CME signal. $\Lambda$($K_{S}^{0}$)-$h^{\pm}$ azimuthal correlations are expected to provide another estimate on the intrinsic background from particle correlations. In addition, theoretical calculations of the Chiral Vortical Effect (CVE) predict a difference in baryon versus anti-baryon azimuthal correlations with respect to the reaction plane. We will present the first measurements of $\Lambda$($K_{S}^{0}$)-$h^{\pm}$ and $\Lambda$-proton azimuthal correlations with respect to the event plane from Au+Au collisions at 39~GeV and 200~GeV from STAR to investigate the CME and CVE predictions. The physics implications of our measurements will also be discussed.

Speaker: Feng Zhao (University of California, Los Angeles)

Slides QM14_FengZhao.pdf

09:40 Effects of magnetic fields on the quark-gluon plasma

In this talk recent lattice QCD results are presented about the response of the thermal QCD vacuum to external (electro)magnetic fields. Characteristic features of this response include the reduction of the deconfinement transition temperature due to the magnetic field and the paramagnetic nature of the QCD vacuum as a medium. The latter results in a squeezing of the quark-gluon plasma if the field is not uniform. Possible implications of this squeezing for heavy-ion collisions are discussed.

Speaker: Gergely Endrodi (U)

Slides qm14.pdf

10:00 Charge asymmetry dependency of $\pi$/K anisotropic flow in U+U and Au+Au collisions at STAR

Theoretical studies [1] indicate that in relativistic heavy collisions a chiral magnetic wave at finite baryon density could induce an electric quadrupole moment, which will lead to a difference in elliptic flow of hadrons with opposite charge. The magnitude of this difference is predicted to be proportional to the charge asymmetry $A_\mathrm{ch}$, defined as $A_\mathrm{ch} \equiv \langle \left (N_{+} -N_{-} \right )/\left ( N_{+} +N_{-} \right ) \rangle$. Charge-asymmetry dependency of the pion elliptic flow has been observed in Au+Au collisions at the STAR experiment. On the other hand, it is argued that the local charge conservation at freeze-out, together with the characteristic shape of $v_{2}(\eta)$ and $v_{2}(p_\mathrm{T})$, may also contribute to elliptic flow splitting as a function of $A_\mathrm{ch}$. This can be manifested by implementing the corresponding measurement for higher flow harmonics $v_{3}$ [2]. Here, we present STAR's measurements of $v_{2}$ and $v_{3}$ for charged pions and kaons at low transverse momentum range (0.15 $< p_\mathrm{T} <$ 0.5 GeV/c), as a function of event charge asymmetry ($A_\mathrm{ch}$) in both U+U collisions at $\sqrt{s_\mathrm{NN}}$ = 193 GeV and Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV. Our measurements for both collision systems serve as important consistency checks for the phenomena suggested as the consequence of the chiral magnetic wave. [1] Burnier Y, Kharzeev D E, Liao J and Yee H U 2011 $\it{Phys. Rev. Lett}$ $\bf{ 107}$ 052303 [2] Bzdak A and Bozek P 2013 $\it{Physics Letters B}$ $\bf{ 726}$ 239-243

Speaker: Qi-Ye Shou (SINAP, BNL)

Slides QM2014_Presentation_QiYeShou_v4.pdf

10:20 Quarks in strong magnetic fields

It has been known that magnetic fields enhance the chiral symmetry breaking (ChSB). According to studies of QED or models of the 4-fermi interactions, it was expected that the enhanced ChSB would resist the chiral restoration effects, increasing critical temperatures for the chiral restoration and deconfinement. Recent lattice calculations, however, showed the opposite behavior: the critical temperatures are reduced as a magnetic field increases. I will discuss how to resolve this apparent paradox, emphasizing which characteristic features of QCD make differences from other models.

Speaker: Toru Kojo (Bielefeld University)

Slides QM14_Kojo.pdf

09:00 → 10:40 Jets: 1

Convener: Peter Levai (Hungarian Academy of Sciences (HU))

announcement QM2014_announcement_Wed.pdf

09:00 Predictions for p+Pb collisions at $\sqrt{s_{_{NN}}} = 5$ TeV: expectations vs. data

A compilation of predictions for charged hadron, identified light hadron, quarkonium, photon, jet and gauge boson production in $p+$Pb collisions at $\sqrt{s_{_{NN}}} = 5$ TeV was made available ahead of the LHC $p+$Pb run [1]. We will compare the predictions to the available data and comment on the reliablity of the predictions. [1] J. Albacete {\it et al.}, Int. J. Mod. Phys. E {\bf 22} (2013) 133007.

Speaker: Ramona Vogt (LLNL)

Transparents qm14.pdf

09:20 Jet and charged hadron nuclear modification factors in pPb and PbPb collisions with CMS

One of the signatures of the strongly interacting medium produced in central PbPb collisions is the suppression of high-$p_{\rm T}$ jets and charged particles. In order to to disentangle the initial state and final state effects in heavy ion collisions, the nuclear modification factor of both jets and of charged-particles in pPb ($R_{\rm pPb}$) and PbPb ($R_{\rm PbPb}$) collisions are presented. The spectra of both jets and charged-particles in pp collisions at $\sqrt{s} = 2.76$, PbPb collisions at $\sqrt{s_{NN}} = 2.76$ TeV, and pPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV, have been measured with the CMS detector using high statistics samples. The $R_{\rm pPb}$ of charged particles is determined by dividing the measured pPb spectrum by a pp reference spectrum constructed using interpolation methods, or alternatively from PYTHIA simulations.

Speaker: Eric Andrew Appelt (Vanderbilt University (US))

Slides QM2014_Appelt_v8.pdf

09:40 Measurement of jet $p_{\rm T}$ spectra and $R_{\rm AA}$ in pp and Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with the ALICE detector

Hard-scattered partons provide an ideal probe for the study of the Quark-Gluon Plasma because they are produced prior to the formation of the QCD medium in heavy-ion collisions. Early measurements conducted at RHIC experiments have provided compelling evidence of jet quenching. In more recent years LHC experiments have confirmed these observations at a higher collisional energy, which allows full jet reconstruction over a much wider kinematic range. Jets are reconstructed in ALICE utilizing both the central tracking system for the charged constituents and the Electromagnetic Calorimeter for the neutral constituents. One of the most important challenges of jet reconstruction in heavy-ion collisions is the large fluctuating background energy density coming from the underlying event. A data-driven method has been used to correct for it which, combined with the unfolding of the detector effects, makes it possible to compare with other experimental results and theoretical predictions. Jet spectra will be reported for Pb-Pb and for pp collisions at a center of mass energy of 2.76 ATeV. The pp measurement serves also as the baseline for the determination of the nuclear modification factor, which shows a strong suppression of jet production in central Pb-Pb collisions. Differential measurements relative to the event plane and centrality class, which make use of data triggered by the Electromagnetic Calorimeter, will aid further investigation of details of this suppression, e.g. regarding the path length dependence of parton energy loss.

Speaker: Salvatore Aiola (Yale University (US))

Slides 2014-05-20-SAiola-QM14JetsALICEv11.pdf

10:00 Measurement of inclusive jet suppression in Pb+Pb

Highly energetic jets produced in relativistic heavy ion collisions provide an important tool to study the QCD medium created in these collisions. These jets suffer energy loss and modification of their parton shower through interactions with the medium— a phenomenon known as jet quenching. A generic feature of such energy loss is the reduction in jet production rates. In this talk, new ATLAS results will be presented on the suppression of inclusive jet production rates in Pb+Pb collisions at 2.76 TeV. Measurements of the nuclear modification factor RAA for fully reconstructed jets will be presented. These measurements cover a large kinematic range in jet transverse momentum and are differential in jet rapidity and collision centrality and provide sensitivity to the details of the quenching mechanism including the values of medium transport coefficients.

Speaker: Aaron Angerami (Columbia University (US))

Slides angerami_QM2014_v2.pdf

10:20 Hydrodynamics and jets in dialogue

We investigate both the medium-induced modifications of jets and the jet-induced modifications of the medium in heavy ion collisions at LHC energies with JEWEL. JEWEL is a fully microscopic Monte Carlo event generator for jet evolution in a dense medium relying on perturbative concepts, that can take any model of the medium as input. We present a detailed comparison between a full viscous hydrodynamic calculation for central events and a simplified, computationally inexpensive model. We also study the modification of the hydrodynamic expansion due to jet energy loss by extracting the local energy and momentum transfer from the jet to the medium. The latter can be used as a source term in the hydrodynamic equations and we discuss its influence.

Speaker: Korinna Christine Zapp (CERN)

Slides qm14.pdf

09:00 → 10:40 Heavy flavor: 4

Convener: Sandra Padula (UNESP - Universidade Estadual Paulista (BR))

announcement QM2014_announcement_Wed.pdf

09:00 Charmonia in pp, pPb and PbPb with CMS

The mechanisms through which charmonia production is modified in the high-density medium created in ultra-relativistic heavy-ion collisions, are still not quantitatively understood. In order to disentangle among different scenarios, a multi-dimensional analysis in a wide kinematic range is needed, in pp, pA and AA collisions, looking at many observables that have different sensitivities to the various aspects of charmonia production. We will report on the prompt $J/\psi$ measurements with the CMS detector, using the 35 nb$^{-1}$ pPb data recorded in 2013 and the 150 $\mu$b$^{-1}$ of PbPb data recorded in 2011. The nuclear modification factors and azimuthal anisotropy in PbPb collisions at 2.76 TeV will be presented. New measurements of the forward to backward ratios in pPb collisions at 5.02 TeV will also be shown. The dependence of all these observables on the prompt $J/\psi$ kinematics, as well as the event characteristics, will be shown. In addition, the comparison of the excited charmonium state ($\psi(2S)$) and the ground state ($J/\psi$) between PbPb and pp is updated, utilizing the pp sample from 2013, which has a factor of 20 higher statistical precision than the 2011 pp data previously presented.

Speaker: Dong Ho Moon (University of Illinois at Chicago (US))

Slides QM2014_dmoon_2014_final_v5.pdf

09:20 J/$\psi$ production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV

The ALICE Experiment at the Large Hadron Collider (LHC) provides unique capabilities to study charmonium production at low transverse momentum. In the early and hottest phase of nucleus-nucleus collisions the formation of a Quark-Gluon Plasma (QGP) is expected. Several QGP induced effects, such as the melting of charmonium states due to color screening and/or a (re)combination of uncorrelated charm and anti-charm quarks, can play a role. A suppression with respect to pp collisions of charmonium states such as the J$/\psi$ was indeed observed in heavy-ion collisions, with the corresponding measurements in pp and p-Pb collisions being crucial for the understanding of the Pb--Pb results. At central (forward) rapidity, corresponding to the range $|y| < 0.9$ ($ 2.5 < y < 4$) , J$/\psi$ are reconstructed via their decay into two electrons (muons) down to zero transverse momentum ($p_\mathrm{T}$). We will present results on the inclusive J$/\psi$ nuclear modification factor $R_\mathrm{AA}$ as a function of collision centrality, rapidity and transverse momentum p_\mathrm{T}, as well as results on the J$/\psi$ $\langle p_\mathrm{T} \rangle$ in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}} = 2.76$ TeV. Furthermore, a separation of prompt and non-prompt components is possible down to $p_\mathrm{T}$ = 1.3 GeV/$c$ at central rapidity and allows a determination of the $R_\mathrm{AA}$ of beauty hadrons and prompt J$/\psi$. These measurements provide, in combination with results from lower energies and theoretical predictions, detailed information on the different mechanisms related to the presence of the hot medium produced in heavy-ion collisions.

Speaker: Julian Book (Johann-Wolfgang-Goethe Univ. (DE))

Slides alice.pdf

09:40 Recent STAR measurements of $J/\psi$ production from Beam Energy Scan and U$+$U collisions

$J/\psi$ suppression in heavy-ion collisions due to color screening of quark and antiquark potential in the deconfined medium has been proposed as a signature of the QGP formation. Other mechanisms, such as the cold nuclear matter effect and charm quark recombination, are likely to contribute to the observed modification of $J/\psi$ production in heavy-ion collisions. Measurements of $J/\psi$ invariant yields in different collision energies, collision systems, and centralities can shed new light on the interplay of these mechanisms for $J/\psi$ production and medium properties. In this presentation we report on new measurements of $J/\psi$ production at midrapidity ($|y| < 1.0$) from the Beam Energy Scan program (Au$+$Au collisions at $\sqrt{s_{NN}} =$ 39 GeV and 62.4 GeV) and U$+$U collisions at $\sqrt{s_{NN}}$ = 193 GeV at STAR. Centrality and transverse momentum dependence of $J/\psi$ invariant yields and the nuclear modification factor ($R_{AA}$) will be presented and compared to those for Au$+$Au collisions at $\sqrt{s_{NN}} =$ 200 GeV and to model calculations. The energy dependence of $J/\psi$ suppression will be discussed.

Speaker: Wangmei Zha (USTC/BNL)

Slides Quark_Matter_2014_ver14.pdf Quark_Matter_2014_ver14.ppt

10:00 Charmonium suppression in a hot medium: melting vs absorption

A colorless $c\bar c$ dipole propagating through a hot medium can be dissolved either due to Debye screening of the binding potential, or by inelastic (color exchange) interaction with the medium, which turns the dipole into a color-octet state (absorption). Both mechanisms are included into the path-integral description of the in-medium propagation of the dipole, providing the real and imaginary parts of the light-cone potential respectively. We found that absorption, which is frequently forgotten, leads to a considerably stronger suppression of $J/\Psi$ production in heavy ion collisions, than the effect of Debye screening.

Speaker: Boris Kopeliovich (UTFSM)

Transparents qm-psi.pdf

10:20 Free energy versus internal energy potential for heavy quark systems at finite temperature

Using the QCD sum rule with its operator product expansion reliably determined from lattice calculations for the pressure and energy density of hot QCD matter, we calculate the strength of the $J/\psi$ wave function at origin and find that it decreases with temperature when the temperature is above the transition temperature. This result is shown to follow exactly that obtained from the solution of the Schr\"odinger equation for a charm and anticharm quark pair with temperature independent quark mass using the free energy from lattice calculations as the potential and is in sharp contrast to that using the deeper potential associated with the internal energy, which shows an enhanced strength of the $J/\psi$ wave function at origin. Our result thus suggests that the free energy potential from lattice calculations is the appropriate heavy quark potential for analyzing the charmonium spectrum at finite temperature.

Speaker: Dr Taesoo Song (Frankfurt Institute of Advanced Studies)

Slides taesoo.pdf

10:40 → 11:10 Coffee break

11:10 → 13:10 Correlations and fluctuations: 1

Convener: Ulrich Heinz (The Ohio State University)

announcement QM2014_announcement_Wed.pdf

11:10 Charge-dependent anisotropic flow and the search for the Chiral Magnetic Wave in ALICE

While no P- or CP-violation has ever been observed in the strong sector of the Standard Model, there is no first principles reason for it not to be present. Theoretical calculations have shown the possibility of P-violating bubbles in the QCD vacuum, which in combination with the strong magnetic field created in off-central heavy-ion collisions leads to the Chiral Magnetic Effect (CME). In addition, a coupling between the CME and the related Chiral Separation Effect produces a wave-like excitation called the Chiral Magnetic Wave (CMW). The CMW produces a quadrupole moment that always has the same sign and is therefore present in an average over events. In this talk we present a series of charge-dependent anisotropic flow measurements in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV in ALICE. The relation of these measurements to the search for the CMW is discussed.

Speaker: Ron Belmont (Wayne State University (US))

Slides qm14.pdf

11:30 Magnetohydrodynamics, charged currents and directed flow in heavy ion collisions

The hot QCD matter produced in any heavy ion collision with a nonzero impact parameter is produced within a strong magnetic field. We study the imprint that these fields leave on the azimuthal distributions and correlations of the produced charged hadrons. The magnetic field is time-dependent and the medium is expanding, which leads to the induction of charged currents due to the combination of Faraday and Hall effects. We find that these currents result in a charge-dependent directed flow $v_1$ that is odd in rapidity and odd under charge exchange. It can be detected by measuring correlations between the directed flow of charged hadrons at different rapidities, $\langle v_1^\pm (y_1) v_1^\pm (y_2) \rangle$

Speaker: Umut Gursoy (University of Utrecht (NL))

Slides Magnetic-currents-Darmstadt.pdf

11:50 Measuring and interpreting charge dependent anisotropic flow as a function of the event charge asymmetry

Recently, the STAR Collaboration has reported a strong dependence of the elliptic flow of positive and negative pions on the net charge density [1]. This measurement attracted a lot of community attention, as the signal appeared to be of the magnitude and the sign of that predicted by the theory of the Chiral Magnetic Wave [2]. At the same time the interpretation of the results and further detailed study of the effect is rather difficult as the observable itself, the slope of elliptic flow value on the observed charge asymmetry in the STAR TPC acceptance, depends on the tracking efficiency and detector acceptance. In this talk we show how one can first make the observable robust (efficiency independent) and then make it suitable for many differential studies, not possible before. We use this observable, a three-particle correlator, in our model calculations to show the sensitivity of the signal to several background effects, such as local charge conservation, and propose experimental tests for further identification of the effects responsible for the observed signal. [1] G.~Wang [STAR Collaboration], ``Search for Chiral Magnetic Effects in High-Energy Nuclear Collisions,'' Nucl.\ Phys.\ A904-905 {\bf 2013}, 248c (2013). [2] Y.~Burnier, D.~E.~Kharzeev, J.~Liao and H.~-U.~Yee, ``Chiral magnetic wave at finite baryon density and the electric quadrupole moment of quark-gluon plasma in heavy ion collisions,'' Phys.\ Rev.\ Lett.\ {\bf 107}, 052303 (2011).

Speaker: Prof. Sergei Voloshin (Wayne State University)

Slides voloshin_qm2014.pdf

12:10 Azimuthal anisotropy of charged particles from multiparticle correlations in pPb and PbPb collisions with CMS

Motivated by two- and four-particle azimuthal correlation measurements that suggest possible collective flow for charged particles emitted in pPb collisions at $\sqrt{s_{NN}}$ =5.02 TeV, we extend the correlation results for these collisions using the six- and eight-particle cumulant methods, and the Lee-Yang Zeros method. CMS has an extensive program studying azimuthal harmonic coefficients for both PbPb and pPb collisions using various methods. The current pPb results will be presented in this context. The data were collected by the CMS experiment at the LHC using both minimum bias and high-multiplicity collision triggers over a wide range in pseudorapidity. The results are compared to 2.76 TeV semi-peripheral PbPb collision data collected in 2011 covering a similar range of particle multiplicities. The second-order azimuthal anisotropy Fourier harmonic ($v_{2}$) is shown for the different methods. A comparison of the six- and greater particle correlations to the previously published two- and four-particle correlation results sheds light on the multiparticle nature of the azimuthal anisotropy. The results are also discussed in terms of recent calculations that explore the role of participant fluctuations on measurements of higher-order particle correlations in pPb collisions.

Speaker: Quan Wang (University of Kansas (US))

Slides QM2014_v2.pdf

12:30 Flow harmonics in Pb+Pb collisions at energy of sqrt(sNN) = 2,76 TeV with the ATLAS detector

We report on measurements of the anisotropy of charged particles in lead-lead collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV, using multi-particle cumulants calculated with the generating function method. The results on the transverse momentum, pseudorapidity and centrality dependence of the elliptic flow (v2) obtained from two-, four-, six- and eight-particle cumulants are presented. Higher-order coefficients, v3 and v4 are also derived using two- and four-particle cumulants and shown as a function of centrality and transverse momentum. A reduction of contributions not related to the initial geometry for vn studied with cumulant expansion of correlations between more than two particles is discussed. Event-by-event fluctuations of the flow harmonics evaluated with multi-particle cumulants as a function of transverse momentum and the collision centrality are also presented. These results are complemented with the pT-integrated elliptic flow measured in the pseudorapidity range |$\eta$|< 2.5 with the event plane method, exploring the range of very low transverse momenta. This was achieved by applying dedicated track reconstruction methods. The centrality dependence of the integrated v2, spanning the range of 0–80% of most central Pb+Pb collisions, is compared to other measurements obtained with higher $p_T$ thresholds. The pseudorapidity dependence of the integrated elliptic flow in different centrality intervals is discussed and compared to the lower energy RHIC data.

Speaker: Dominik Karol Derendarz (Polish Academy of Sciences (PL))

Slides qm2014_Derendarz2.pdf

12:50 New universal parametrization of initial-state fluctuations and its application to event-by-event anisotropy

We propose a new, universal parametrization of the probability distribution of initial anisotropies in proton-proton, proton-nucleus and nucleus-nucleus collisions. The distribution of fluctuation-driven anisotropies, such as the initial triangularity $\varepsilon_3$, is described by a one-parameter power distribution. When a mean anisotropy in the reaction plane is also present, as in the case of the the initial eccentricity $\varepsilon_2$ in nucleus-nucleus collision, a new parameter must be added: the power distribution is replaced by a new, elliptic power distribution. Our results are in excellent agreement with all Monte-Carlo models of the initial state (Glauber, KLN, IP-Glasma) for all collision systems and all centralities. We then apply our results to the interpretation of the event-by-event distributions of $v_2$ and $v_3$ recently measured by the ATLAS collaboration in Pb-Pb collisions at the LHC. Assuming that anisotropic flow is proportional to the initial anisotropy, $v_n=C_n\varepsilon_n$, we obtain excellent fits to these data. This procedure gives us direct information on the initial state from data. Our results are compared to several initial-state models. We are also able to extract the hydrodynamic response $C_n$ for $n=2,3$ as a function of centrality, without assuming any particular model for the initial state. These results are compared with viscous hydrodynamic calculations of the response. L. Yan and J. Y. Ollitrault, "Universal fluctuation-driven eccentricities in proton-nucleus and nucleus-nucleus collisions,'' arXiv:1312.6555 [nucl-th], to appear in Phys. Rev. Lett. L. Yan, A. M. Poskanzer and J. Y. Ollitrault, in preparation.

Speaker: Li Yan

Slides qm2014talk_yan.pdf

11:10 → 13:10 QCD at high temperature and/or density

Convener: Rajiv V Gavai (Tata Institute, Mumbai, India)

announcement announcement-tuesday.pdf

11:10 Three loop HTL perturbation theory at finite temperature and chemical potential

We present results of a three-loop hard-thermal-loop perturbation theory (HTLpt) calculation of the thermodynamic potential of a finite temperature and chemical potential system of quarks and gluons. We compare the resulting pressure, energy density, etc., and the diagonal/off-diagonal quark susceptibilities with lattice data. We show that there there is good agreement between the three-loop HTLpt analytic result and available lattice data.

Speaker: Michael Strickland (Kent State University)

Slides strickland.pdf

11:30 Hadronic resonance production measured by ALICE at the LHC

Hadronic resonances constitute a valuable probe for the properties of the medium formed in heavy-ion collisions. In particular, they provide information on particle-formation mechanisms, the properties of the medium at freeze-out, and they contribute to the systematic study of energy loss and recombination. The study of resonance production in other collision systems such as pp and p-Pb form a necessary baseline to disentangle initial-state effects from genuine medium-induced effects. The ALICE experiment has measured the production of the K(892)$^{0}$ and $\phi$(1020) resonances at mid-rapidity in different collision systems at LHC energies. Resonances are reconstructed via their hadronic decay in a wide momentum range, by exploiting the excellent particle-identification capabilities of the Time-Projection Chamber and the Time-of-Flight system. The first results on K(892)$^{0}$ and $\phi$(1020) production in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV at the LHC will be presented. The resonance mass and width, transverse momentum spectra and yields are measured and reported as a function of the multiplicity of the p-Pb collision. Ratios of resonance to long-lived hadron production in Pb-Pb are compared with the same quantities measured in pp and p-Pb collisions, in order to investigate re-scattering effects. The nuclear modification factors ($R_{\rm AA}$, $R_{\rm pPb}$), recently measured up to high $p_{\mathrm{T}}$ for resonances, are compared to the same measurement for long lived hadrons. The results are discussed in comparison with measurements at lower energies and theoretical predictions.

Speaker: Francesca Bellini (Universita e INFN (IT))

Slides ALICE_FB_20may14.pdf

11:50 The QCD Equation of State at $\mathbf{\mathcal{O}(\mu_B^4)}$

Hydrodynamic models of heavy-ion collisions have increasingly begun to rely on lattice results for the Equation of State[1]. While the lattice has the advantage of being a first-principles approach to QCD, the notorious sign problem prevents a direct determination of the equation of state and other thermodynamic observables at finite baryon chemical potential $\mu_B$. In our talk, we will present results from a high-statistics calculation of all the Taylor coefficients upto sixth order in a $(\mu_B,\mu_Q,\mu_S)$-expansion of the pressure. Our calculation allows us to extrapolate, for the first time, the equation of state on the freezeout curve upto $\mathcal{O}(\mu_B^4)$ while our sixth-order results show that the truncation error is not more than a few % upto $\mu_B/T\sim1.5$. Thus our equation of state should be useful in describing both the LHC results as well as results from RHIC beam energy scan down to $\sim$20 GeV. We will also use our results to construct the isentropic equation of state for strangeness-neutral systems. Our lattice QCD calculations make use of the gauge ensembles generated using the HISQ action[2,3]. Our lattice sizes range from $6\times24^3$ to $12\times48^3$. The pion mass ($\sim$160 MeV) is nearly equal to its physical value while the strange quark mass has been set to exactly its physical value. **References** [1] See for e.g. C. Gale, S. Jeon and B. Schenke, Int. J. Mod. Phys. **A28**, 1340011 (2013); C. Shen, U. Heinz, P. Huovinen and H. Song, Phys. Rev. **C82**, 054904 (2010). [2] A. Bazavov *et al.* [HotQCD Collaboration], Phys. Rev. **D86**, 035409 (2012). [3] A. Bazavov, H.-T. Ding, P. Hegde, O. Kaczmarek, F. Karsch, E. Laermann, Y. Maezawa, S. Mukherjee, H. Ohno, P. Petreczky, C. Schmidt, S. Sharma, W. Soeldner and M. Wagner, Phys. Rev. Lett. **111**, 082301 (2013).

Speaker: Dr Prasad Hegde (Central China Normal University)

Slides Presentation slides

12:10 Simulating full QCD at nonzero density using the complex Langevin equation

The complex Langevin method is extended to full QCD at non-zero chemical potential. The method evades the sign problem which makes naive simulations at nonzero density impossible. The procedure 'gauge cooling' is used to stabilize the simulations at small enough lattice spacings. The method allows simulations also at high densities, all the way up to saturation. The method is validated in the small chemical potential region, where the sign problem is mild, and the reweighting approach is also feasible.

Speaker: Denes Sexty (University of Heidelberg)

Slides sexty_qm2014.pdf

12:30 Vector screening masses in the quark-gluon plasma and their physical significance

Static and non-static thermal screening states that couple to the conserved vector current are investigated in the high-temperature phase of QCD. Their masses and couplings to the current are determined at weak coupling, as well as using two-flavor lattice QCD simulations. A consistent picture emerges from the comparison, providing evidence that non-static Matsubara modes can indeed be treated perturbatively. We elaborate on the physical significance of the screening masses.

Speaker: Prof. Harvey B. Meyer (Joh. Gutenberg University Mainz)

Slides meyerhQM14.pdf

12:50 The QCD equation of state

The quark-gluon plasma (QGP), the deconfined high-temperature phase of QCD, is currently under extensive investigation in heavy-ion collision experiments at RHIC and LHC. The transition from the hadronic, low-temperature phase to the QGP is a rapid crossover, manifested by a significant change in bulk thermodynamic quantities. A fundamental characteristic of QCD is the equation of state, which is also an essential ingredient of hydrodynamic modeling of heavy-ion collisions. We report our final result for the 2+1 flavor QCD equation of state in the continuum limit. We calculate the pressure, energy density and other thermodynamic quantities in the experimentally relevant temperature range $140-400$ MeV. We use the highly improved staggered quark (HISQ) action with the Goldstone pion mass tuned to about $160$ MeV in the continuum limit. To perform the continuum extrapolation we use lattices with temporal extent $N_\tau=6$, $8$, $10$ and $12$.

Speaker: Alexei Bazavov (University of Iowa)

Slides bazavov_qm2014.pdf

11:10 → 13:10 Jets: 2

Convener: John William Harris (Yale University (US))

announcement QM2014_announcement_Wed.pdf

11:10 Jet quenching from the lattice

We present a lattice study of the momentum broadening experienced by a hard parton in the quark-gluon plasma. In particular, the contributions to this real-time phenomenon from soft modes are extracted from a set of gauge-invariant operators in a dimensionally reduced effective theory (electrostatic QCD), which can be simulated on a Euclidean lattice. At the temperatures accessible to present experiments, the soft contributions to the jet quenching parameter are found to be quite large. We compare our results to phenomenological models and to holographic computations.

Speaker: Marco Panero (IFT UAM/CSIC)

Slides qm2014.pdf

11:30 Measurements of charged particle spectra and nuclear modification factors in proton-lead and lead-lead collisions with the ATLAS detector

The measurement of charged particle spectra in heavy ion collisions carries important information about the properties of hot and dense matter created in these interactions. Spectra measured in lead-lead collisions at different centralities can be compared to the proton-proton spectra giving quantitative information about the properties of such matter. Proton-nucleus collisions provide further means for understanding the role of the initial state effects modifying the hard scattering rates. The ATLAS detector at the LHC obtained the sample of Pb+Pb data at  $\sqrt{s_{\rm NN}}$ = 2.76 TeV with integrated luminosity 0.15 $nb^{-1}$, which can be compared to recently obtained pp sample of 4.5 $pb^{-1}$ sample at the same energy. The p+Pb data at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with integrated luminosity 30 $nb^{-1}$ can also be compared to the pp data obtained by interpolating pp measurements at $\sqrt{s}$ = 2.76 TeV and 7 TeV. Due to the excellent capabilities of the ATLAS detector, and its stable operation in heavy ion as well as proton-proton physics runs, the data allow measurements of the nuclear modification factor out to transverse momentum limited only by the statistics of the accumulated samples and studying the ratios of HI charged particle spectra divided by pp reference in different centrality bins over a wide range of pseudorapidity.

Speaker: Petr Balek (Charles University (CZ))

Slides PetrBalek_QM2014.pdf

11:50 Qualitative extraction of qhat from combined jet quenching at RHIC and LHC

On behalf the JET Collaboration Within five different approaches to parton propagation and energy loss in dense matter, a phenomenological study of experimental data on suppression of large $p_T$ single inclusive hadrons in heavy-ion collisions at both RHIC and LHC was carried out. The evolution of bulk medium used in the study for parton propagation was given by 2+1D or 3+1D hydrodynamic models which are also constrained by experimental data on bulk hadron spectra. Values for the jet transport parameter $\hat q$ at the center of the most central heavy-ion collisions are extracted or calculated within each model, with parameters for the medium properties that are constrained by experimental data on the hadron suppression factor $R_{AA}$. For a quark with initial energy of 10 GeV we find that $\hat q\approx 1.2 \pm 0.3$ GeV$^2$/fm at an initial time $\tau_0=0.6$ fm/$c$ in Au+Au collisions at $\sqrt{s}=200$ GeV/n and $\hat q\approx 1.9 \pm 0.7 $ GeV$^2$/fm in Pb+Pb collisions at $\sqrt{s}=2.76 $ TeV/n. Compared to earlier studies, these represent significant convergence on values of the extracted jet transport parameter, reflecting recent advances in theory and the availability of new experiment data from the LHC.

Speaker: Xin-Nian Wang (Central China Normal University/Lawrence Berkeley National Lab)

Slides qm14-xnwang.pdf

12:10 Azimuthal jet tomography at RHIC and LHC

Recent data on the azimuthal and transverse momentum dependence of high-pT pion nuclear modification factors and high-pT elliptic flow in nuclear collisions at RHIC and LHC are analyzed in terms of a generic dE/dx model that interpolates between running coupling pQCD-based models such as CUJET2.0 and AdS/CFT-inspired holographic models. The jet-energy loss models are coupled to state of the art viscous hydrodynamic fields. RHIC data are found to be surprisingly consistent with most dE/dx+Hydro models, but extrapolations to LHC energies favor running coupling QCD-based energy-loss models, while conformal holography models are inconsistent with the data. It is also shown that energy-loss fluctuations appear to play a crucial role in the underprediction of high-pT elliptic flow as seen by various pQCD-based energy-loss approximations.

Speaker: Barbara Betz (Frankfurt University)

Slides Betz_QM2014_v2.pdf

12:30 Centrality and rapidity dependence of inclusive jet production in p+Pb collisions at 5.02 TeV with the ATLAS detector

Measurements of reconstructed jets in high-energy proton-nucleus collisions over a wide rapidity and transverse momentum range are a fundamental probe of the partonic structure of nuclei. Inclusive jet production is sensitive to the modification of parton distribution functions in the high-density nuclear environment. In the forward direction and at small pT jets may even explore the transition from a dilute to saturated partonic system. Furthermore, any modification of jet production in p+A collisions has implications for our understanding of the strong suppression seen in central A+A collisions. We present the latest results on inclusive jet production in 31/nb of proton-lead collisions at 5.02 TeV with the ATLAS detector at the LHC. The centrality of p+Pb events is determined by applying the Glauber model to the sum of the transverse energy in the Pb-going forward calorimeter. The jet yields in central and peripheral p+Pb collisions are found to be suppressed and enhanced, respectively, relative to geometric expectations. Furthermore, the modifications at all rapidities are seen to be consistent with a simple function of the total jet energy.

Speaker: Dennis Vadimovich Perepelitsa (Brookhaven National Laboratory (US))

Slides dvp-QM14-5-20-14.pdf

12:50 Centrality, rapidity and pT dependence of isolated prompt photon production in lead-lead collisions at sqrt(sNN)= 2.76 TeV with the ATLAS detector at the LHC

ATLAS has measured prompt photon production in sqrt(s_NN) = 2.76 TeV Pb+Pb collisions using data collected in 2011 with an integrated luminosity of 0.14 nb-1. The measurement is performed with a hermetic, longitudinally segmented calorimeter, which gives excellent spatial and energy resolution, and detailed information about the shower shape of each measured photon. A multi-parameter selection on a set of nine shower properties, coupled with an isolation criterion based on the energy deposited in the cone around a photon, gives measured purities ranging from 50% at low pT to greater than 90% at high pT. Photon yields, scaled by the mean nuclear thickness function, will be presented as a function of collision centrality, pseudorapidity (in two intervals |eta| < 1.37 and 1.52 < |eta|< 2.37) and transverse momentum (from 22 < pT < 280 GeV). The scaled yields will be compared to expectations from JETPHOX (perturbative QCD calculations at next to leading order), as are the ratios of the forward yields to those near mid-rapidity.

Speaker: Peter Alan Steinberg (Brookhaven National Laboratory (US))

Slides Steinberg_QM2014_v4.pdf

11:10 → 13:10 New theoretical developments

Convener: Prof. Gennady Zinovjev (National Academy of Sciences of Ukraine (UA))

announcement announcement-tuesday.pdf

11:10 Center Domains and Their Phenomenological Consequences in Ultrarelativistic Heavy Ion Collisions

In this talk, we first argue that a domain structure, which can be inferred from the properties of the Polyakov loop and and is called center domains, is created in the deconfined QCD matter in the early stage of ultrarelativistic heavy ion collisions. Its formation is assisted by the gauge configuration in the glasma state created right after the collisions. Then we show that the center domains are an important facet of the evolution of the quark-gluon plasma from its birth up to hadronization. They naturally explain the strongly coupled nature of the quark gluon plasma including its major observed properties from its nearly ideal hydrodynamical behavior to strong jet quenching.

Speaker: Masayuki Asakawa (Osaka University)

Slides QM2014Asakawa.pdf

11:30 New approach to lattice QCD thermodynamics from Yang-Mills gradient flow

A novel method to study the bulk thermodynamics in lattice gauge theory is proposed on the basis of the Yang-Mills gradient flow with a fictitious time t. The energy density (epsilon) and the pressure (P) of SU(3) gauge theory at fixed temperature are calculated directly on 32$^3 \times$ (6,8,10) lattices from the thermal average of the well-defined energy-momentum tensor ($T_{\mu \nu}^R(x)$) obtained by the gradient flow. It is demonstrated that the continuum limit can be taken in a controlled manner from the t-dependence of the flowed data. [1] M. Asakawa, T. Hatsuda, E. Itou, M. Kitazawa and H. Suzuki [FlowQCD Coll.], arXiv:1312.7492 [hep-lat].

Speaker: Dr Tetsuo Hatsuda (RIKEN)

Slides Hatsuda_qm14.pdf

11:50 Collisions in AdS: the road to experiments

Holography has been used for a while as a strongly coupled approach to study the initial stage of heavy-ion collisions. As holographic calculations cannot directly describe QCD, importantly neglecting any weak-coupling effects, it is an interesting question how well these studies fit experimental data. Here, we will focus on longitudinal dynamics, modeled by colliding shock waves in AdS. These collisions give a surprisingly universal rapidity profile, where the shape at high collision energies is completely independent of the energy or longitudinal structure of the colliding shocks. It is somewhat complicated to compare this initial profile to the final measured rapidity profile, but we can compute the entropy and thereby make an estimate of the total multiplicity. The result indicates that our infinite coupling profile has somewhat more stopping than in real heavy-ion collisions, which is most likely because of neglecting weak-coupling effects. We finally comment on (future) consequences for real nucleus-nucleus and proton-nucleus collisions. References: arxiv:1312.2956 and 1305.4919 (PRL 111)

Speaker: Wilke van der Schee (Utrecht University)

Slides Talk_QM.pptx

12:10 Rapidity evolution of Wilson lines at the next-to-leading order: Balitsky-JIMWLK equation at NLO

Scattering amplitudes of proton-Nucleus or Nucleus-Nucleus collisions at high-energy are described by matrix elements of Wilson line operators - infinite gauge factors ordered along the straight lines of the fast moving particles. The energy dependence of such amplitudes is described by the evolution equation of Wilson lines with respect to the rapidity parameter - the Balitsky-JIMWLK evolution equation. Most of the current phenomenology of high-energy and high-density QCD is based on the leading-order evolution equation with only running coupling corrections. In my talk I will present the derivation of the Balitsky-JIMWLK evolution equation at the next-to-leading order.

Speaker: Giovanni Antonio Chirilli (The Ohio State University)

Slides QM14-Chirilli.pdf

12:30 Relating classical strings and gravitons in AdS/CFT jet quenching

Here's a fun question in gravity: What happens when a high-momentum graviton falls into a large (AdS-)black hole? Answer: Tidal forces outside the black hole can stretch the graviton from a quantum string into a large, classical string. What does this have to do with theory investigations related to jet quenching in strongly coupled plasmas? It provides a link between two very different methods that have been used to set up "jet stopping" problems in such plasmas---methods which have given parametrically different results.

Speaker: Peter Arnold (University of Virginia)

Slides qm14.pdf

12:50 Thermalization of over-occupied gluons

In the weak coupling limit, the color-glass condensate framework predicts that the initial conditions of heavy-ion collisions are characterized by intense gauge fields, or equivalently high occupation numbers of gluons. In my talk, I will describe how such initial conditions relax towards thermal equilibrium. In particular, I will discuss how such a system has dual descriptions in terms of either classical gauge field theory or effective kinetic theory of gluons. The domain of validity of the two descriptions is overlapping and I will numerically demonstrate the equivalence in the case of a non-expanding system.

Speaker: Eero Aleksi Kurkela (CERN)

Slides Kurkela.pdf

13:10 → 14:20 Lunch

14:20 → 16:00 Correlations and fluctuations: 2

Convener: George Fai (U)

announcement QM2014_announcement_Wed.pdf

14:20 Pseudorapidity dependence of near-side and away-side long-range correlations in pPb collisions with CMS

Two-particle long-range pseudorapidity ($\Delta$$\eta$) correlations are observed in pPb collisions at the LHC. Previous correlation measurements have been averaged over both the trigger and associated particle $\eta$. In order to explore the possible pseudorapidity dependence of the long-range correlations in asymmetric pPb collisions, a new analysis of two-particle correlations with trigger particles at various fixed eta locations is presented. The data were collected during the 2013 LHC pPb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment, with a wide eta coverage of -2.4<$\eta$<2.4. The near-side $\Delta$$\eta$ correlations are decomposed into short-range (jet) and long-range components. The away-side long-range correlations in central collisions are also studied by subtracting back-to-back jet contributions, modeled by the away-side correlations from peripheral collisions after accounting for the biases introduced by the multiplicity classification. The long-range correlations are found to be dependent on pseudorapidity. The observed pseudo-rapidity dependence may potentially discriminate theoretical models for long-range two-particle correlations observed in pPb collisions.

Speaker: Lingshan Xu (Purdue University (US))

Slides QM2014_dihadron_eta_v6.pdf

14:40 Long-range angular correlations at the LHC with ALICE

The observation of long-range correlations on the near- and away-side (also known as the double-ridge) in high-multiplicity p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and its similarity to Pb-Pb collisions remains one of the open questions from the p-Pb run at the Large Hadron Collider. It has been attributed to mechanisms that involve initial-state effects, such as gluon saturation and colour connections forming along the longitudinal direction, and final-state effects, such as parton-induced interactions and collective effects developing in a high-density system possibly formed in these collisions. In order to understand the nature of this double-ridge structure the two-particle correlation analysis has been extended to identified particles. The observed mass dependence in p-Pb resembles qualitative expectations from hydrodynamics, and is also observed in Pb-Pb collisions. A study of correlations at forward rapidity probes the low-x regime of the nucleus, where saturation effects are expected to become stronger. The possibility of accessing this regime using the ALICE forward muon detector is explored. In addition, a possible ridge signal within the ALICE acceptance in pp collisions $\sqrt{s} = 7$ TeV is also investigated.

Speaker: Leonardo Milano (CERN)

Slides LM_QM2014.pdf

15:00 Measurement of the long-range pseudorapidity correlations and associated Fourier harmonics in 5.02 TeV proton-lead collisions with the ATLAS detector

Detailed measurement of the Fourier harmonics ($v_n$) associated with the azimuthal modulation of two-particle correlation structures over $-5 < \delta\eta < 5$ in 31 nb$^{-1}$ p + Pb collisions are presented. The $v_n$ results are presented as a function of $p_T$, \eta, and event activity characterized by the number of reconstructed tracks in $-2.5 < \eta < 2.5$, and the total transverse energy on the Pb-going side ($3.2 < \eta < 4.9$). The elliptic, triangular, and quadrangular coefficients, $v_2$, $v_3$ and $v_4$, are extracted for $0.5 < p_T < 15$ GeV, significantly extending the previous measurements. The v_n values are found to reach a maximum around 3-5 GeV and then decrease to a finite positive values at $p_T > 10$ GeV, similar to the behavior seen in Pb+Pb collisions. Evidence for rapidity-even dipolar flow $v_1$ is also observed, further supporting a collective origin of the long-range two-particle correlations. The first measurement of the eta dependence of these correlations suggests that the $v_2$ values are smaller in the proton-going side than those in the Pb-going side. Finally $v_n$ results are also extracted with four-particle cumulant method and compared with those obtained with two-particle correlation method. These results provide new important insights on the physics underlying the long-range pseudorapidity correlations.

Speaker: Sooraj Krishnan Radhakrishnan (State University of New York (US))

Slides pPb_ridge_-_QM14_-_ver5.pdf

15:20 Long range rapidity correlations and $v_2$ of identified particles in $d$$+$Au collisions

Traditionally $p(d)$$+$A collisions at RHIC and the LHC were considered as a tool to study cold nuclear matter effects. Production of the hot and dense medium in such collisions was not expected. However recent measurements has challenged this assumption with the observation of long-range correlations in angular distributions of hadron pairs with low transverse momentum. The observed modulations are very similar to those previously seen in A$+$A collisions which are widely thought to arise from hydrodynamic flow. The same hydrodynamic models used in heavy ion collisions have been successful in describing the $p(d)$$+$A results. However the long-range correlations observed in $p(d)$$+$A collisions can also be qualitatively described within the Color Glass Condensate models. In this talk we present new PHENIX results for azimuthal angular correlations between charged hadrons measured at mid-rapidity ($|\eta|<0.35$) and energy deposited in calorimeter towers in the Au-going direction at large rapidity ($-3.7<\eta<-3.1$) in central $d$$+$Au collisions at $\sqrt{s_{NN}} = 200$~GeV. We report the first direct evidence for enhanced near-side angular correlations across $|\Delta\eta| > 2.75$ at RHIC. We also present the first measurement of $v_2$ for identified charged pions and (anti-)protons in $d$$+$Au at RHIC, and observe a mass-ordering pattern similar to that seen in A$+$A collisions.

Speaker: Dr shengli huang (PHENIX Collaboration)

Slides QM2014_ShengliHuang3.pdf QM2014_ShengliHuang3.pptx

15:40 Studies of two-particle correlations with identified $\pi^0$, $K^0_s$ and Lambdas in pPb and PbPb collisions with CMS

Observation of a long-range near-side two-particle correlation (known as the "Ridge") in high-multiplicity pp and pPb collisions opened up new opportunities of exploring novel QCD dynamics in small collision systems. To further investigate the origin of this phenomenon, new measurements of two-particle correlations with identified $\pi^0$, $K^0_s$ and Lambda trigger particles in 5.02 TeV pPb and 2.76 TeV PbPb collisions are presented. One unique feature of this analysis is the implementation of a high-multiplicity trigger during the 2013 LHC pPb run, which enables the correlation studies to be performed up to a multiplicity range that is comparable to mid-central PbPb collisions at 2.76 TeV. The $K^0_s$ and Lambdas are cleanly reconstructed via their secondary decay vertices over a wide pseudorapidity and transverse momentum range 0.2 $< p_T <$ 6 GeV/c. Neutral pions are reconstructed through the decay channel of two photons in the $p_T$ range of 0.7-5.0 GeV/c. The second-order ($v_2$) and third-order ($v_3$) anisotropy harmonics of $\pi^0$, $K^0_s$ and Lambda are extracted from long-range correlations as a function of particle multiplicity and $p_T$. The wide $p_T$ coverage and rich sample of high multiplicity pPb events allow: (1) a precise examination of the mass ordering effect of $v_n$ at low $p_T$ as predicted by hydrodynamics for a collectively expanding medium; (2) exploration of possible constituent quark number scaling of $v_2$ and $v_3$ between mesons and baryons as was observed in high-energy nucleus-nucleus collisions.

Speaker: Monika Sharma (Vanderbilt University (US))

Slides QM2014_MonikaSharma.pdf

14:20 → 16:00 QCD phase diagram: 2

Convener: Helen Louise Caines (Yale University (US))

announcement QM2014_announcement_Wed.pdf

14:20 Lattice QCD based equation of state at finite baryon density

The effects of non-zero baryon density are expected to become important in hydrodynamic modeling of heavy collisions below the highest energy at RHIC. Recent calculations in effective models and in QCD using Dyson Schwinger equation suggest that the transition in QCD remains a crossover up to baryon chemical potentials of about 800MeV [1]. If so, the equation of state relevant for hydrodynamic models can be calculated on the lattice using Taylor expansion. However, except for the coefficients of the lowest order, there are large cutoff effects in present lattice calculations for non-zero chemical potentials. To extend our previous parametrization of the equation of state [2] to finite baryon density, we employ the continuum extrapolated lattice QCD data on Taylor expansion coefficients in order two [3], and complement them with coefficients in order four and six evaluated using p4 action [4]. To avoid large cutoff efects these coefficients are smoothly matched to those of hadron resonance gas at low temperature. Some preliminary results were reported in [5]. We also show how the hydrodynamical evolution is affected by this equation of state in the energy range relevant for SPS and the RHIC energy scan. [1] T.K. Herbst et al, Phys. Lett. B696 (2011); C.S. Fischer et al, Phys. Lett. B702 (2011) [2] P.Huovinen and P.Petreczky, Nucl.Phys. A837 (2010) 26 [3] S. Borsanyi et al, JHEP 1208 (2012) 053; A. Bazavov et al, Phys. Rev. D86 (2012) 034509 [4] M. Cheng et al, Phys. Rev. D79 (2009) 074505; C Miao and C. Schmidt, PoS LATTICE2008 (2008) 172 [5] P. Huovinen, P. Petreczky and C. Schmidt, Central Eur. J. Phys. 10, (2012) 1385

Speaker: Pasi Huovinen (Johann Wolfgang Goethe-Universität)

Slides talk.pdf

14:40 Locating the CEP

I review resent results on the chiral and deconfinement transitions of QCD and the associated phase diagram obtained from a combination of lattice results with the framework of Dyson-Schwinger equations. At zero chemical potential we find excellent agreement with existing lattice results. We discuss the potential location of the critical endpoint for Nf=2+1 and Nf=2+1+1 flavors and present first results for the Polyakov potential at finite chemical potential.

Speaker: Prof. Christian Fischer (JLU Giessen)

Slides QM_Fischer.pdf

15:00 PHENIX beam energy scan results

The Beam Energy Scan (BES) program at RHIC has shown the flexibility to vary the beam energy per nucleon by more than an order of magnitude, down to the equivalent $\sqrt{s_{NN}}$ of SPS fixed-target collisions and below. This allows the RHIC experiments to systematically track the evolution of excited nuclear matter as it crosses the QGP transition, and to explore new physics at significant net baryon density such as the possibility of a QCD critical point at high $\mu_B$. We present new results from PHENIX on the beam-energy dependence of observables including hydrodynamic flow parameters, 3D HBT source shapes, and global multiplicity and $E_T$ production. We also discuss plans to utilize the upcoming BES-II running period at RHIC.

Speaker: Dr Ron Soltz (Lawrence Livermore Nat. Laboratory (US))

Slides qm14_phenix_bes_soltz_v6.pdf qm14_phenix_bes_soltz_v6.pptx

15:20 Reviewing hadron production in the SIS energy regime using new HADES Au+Au data

Data on particle production in heavy ion collisions in the energy regime of 1-2 A GeV have been collected over almost three decades now. As most of the newly created hadrons are produced below or slightly above their free NN-thresholds, data are usually interpreted with the help of phenomenological models, rather than comparing to elementary reference measurements. Driven by advance in detector technology, more and more rare and penetrating probes have become accessible, and still keep challenging our knowledge about the properties of the created system and its dynamical evolution. The recently collected HADES data from Au+Au collisions at 1.23 A GeV represents in this energy regime the most advanced sample of heavy ion collisions in terms of precision and statistics (7*10$^{9}$ collected events). Using the yields and spectra of reconstructed hadrons ($\pi^{+-}, K^{+-},K^{0}_{s}, \Lambda$) provides therefore the optimal bases to test state of the art models and to question the extent of our present understanding of hadron production. This work has been supported by BMBF (05P12RFGHJ), Helmholtz Alliance EMMI, HIC for FAIR, HGS-HIRe.

Speaker: Dr Manuel Lorenz (GU Frankfurt)

Slides QM14_lorenz.pdf

15:40 Spectral functions from the functional renormalization group

We present a new method to obtain real-time quantities such as spectral functions and transport coefficients at finite temperature and density using a non-perturbative Functional Renormalization Group approach [1]. Our method is based on a thermodynamically consistent truncation of the flow equations for 2-point functions with analytically continued frequency components in the originally Euclidean external momenta. We demonstrate the feasibility of our method by calculating the mesonic spectral functions in the quark-meson model at different temperatures and values of the quark chemical potential, in particular near the critical endpoint of the corresponding phase diagram. [1] Tripolt, Strodthoff, von Smekal, Wambach, Phys. Rev. D 89, 034010 (2014)

Speaker: Ralf-Arno Tripolt (TU Darmstadt)

notes spectral_functions.mp4

Slides tripolt.pdf

14:20 → 16:00 Jets: 3

Convener: James Nagle (Unknown)

announcement QM2014_announcement_Wed.pdf

14:20 Measurement of hadron composition in charged jets from pp collisions with the ALICE experiment

Jets are defined in QCD as cascades of consecutive emission of partons from an initial hard scattering. The process of parton showering and subsequent hadronisation is broadly known as fragmentation. Identified particles in the final state provide an enhanced sensitivity to the flavor dependence of fragmentation. ALICE at the CERN LHC is a general-purpose heavy ion experiment designed to study the physics of strongly interacting matter. It provides excellent tracking and particle identification. Charged pions, kaons and (anti-)protons are identified using the TPC specific energy loss (d$E$/d$x$) in the momentum range up to about 40 GeV/$c$. In this talk we present novel measurements of hadron composition ($\pi$/K/p) of charged jets from pp collisions at $\sqrt{\rm s} = 7$ TeV. The results are compared to model calculations and the implications for identified hadron fragmentation functions are discussed.

Speaker: Xianguo Lu (Ruprecht-Karls-Universitaet Heidelberg (DE))

Slides 2014-May-18-conferencefile-QM14_xglu_v12.0.pdf

14:40 Jet fragmentation in lead-lead collisions at 2.76 TeV using the ATLAS detector at LHC

Measurements of charged particle fragmentation functions of jets produced in ultra-relativistic nuclear collisions are expected to provide insight on the modification of parton showers in the hot and dense medium created in the collisions. ATLAS has measured jets at sqrt{sNN}=2.76 TeV in Pb+Pb collisions using data collected during 2011 run and in p+p collisions using 2013 run. Jets were reconstructed using the anti-kt algorithm with distance parameter values R=0.2, 0.3, and 0.4. Distributions of charged particle transverse momentum and longitudinal momentum fraction are reported for seven bins in collision centrality. The ratios of fragmentation distributions with respect to the p+p reference fragmentation functions are evaluated. The jet structure is further investigated in terms of correlations of an angular position and momenta of a particle within jet.

Speaker: Martin Spousta (Columbia University and Charles University)

Slides Spousta_QM2014_20140509_v1.pdf

15:00 Neutral meson production in pp and Pb-Pb collisions measured by ALICE at LHC

The ALICE experiment at LHC performs measurements of neutral meson inclusive spectra in mid-rapidity in a wide $p_{\rm T}$ range in pp, p-Pb and Pb-Pb collisions, as well as correlations between leading $\pi^0$ and charged hadrons. Neutral mesons $\pi^0$, $\eta$, $\omega$ are reconstructed via complementary methods, using the ALICE electromagnetic calorimeters and by the central tracking system identifying photons converted to $e^+e^-$ pairs in the material of the inner barrel detectors. Measurements of neutral meson spectra in pp collisions at energies $\sqrt{s}$ = 0.9, 2.76, 7 TeV provide valuable data for pQCD calculations and allow to study scaling properties of hadron production at the LHC energies. The study of neutral meson production in p-Pb collisions at $\sqrt{s} = 5.02$ TeV is of importance to confirm that the strong suppresion observed in central Pb-Pb collisions is a final-state effect of the produced dense medium. The nuclear modification factor $R_{\rm AA}$ of the $\pi^0$ production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV at different collision centralities shows a clear pattern of strong suppression in a hot QCD medium with respect to pp collisions. We shall also present the current status of correlation measurements between $\pi^0$ or isolated photons triggered by the electromagnetic calorimeter EMCAL, and charged hadrons detected in the central tracker.

Speaker: Ana Marin (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

Slides QM2014_marin.pdf

15:20 Production of strange particles in charged jets and underlying event in p--Pb and Pb--Pb collisions with ALICE

Properties of the hot and dense strongly interacting matter created in ultra-relativistic heavy-ion collisions can be studied using jets. Hadronization processes occurring in jets are expected to be modified by the interaction of partons with the medium. At intermediate $p_{\rm T}$, a strong increase of the baryon/meson ratio is observed for inclusive light particles produced in heavy-ion collisions when compared to the ratio measured in proton-proton collisions. Production by fragmentation cannot explain this phenomenon and other hadronization mechanisms, like coalescence or parton recombination, have been proposed instead. Measurements of spectra of identified particles produced in jets in heavy-ion collisions will provide further important insights into the interplay of hadronization processes which participate in the jet fragmentation in a medium dominated by the strong interaction under high temperatures and high energy densities. In this talk, we present the first measurements of the $p_{\rm T}$ spectra of $\Lambda$ and $\overline{\Lambda}$ baryons and $\rm{K_s^0}$ mesons produced in association with charged jets in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV and p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV measured by ALICE at the LHC, exploiting the excellent particle identification capabilities of this experiment. Baryon/meson ratios of the spectra of strange particles associated with jets are studied as a function of centrality and are compared to the ratios obtained for inclusive particles and for particles coming from the underlying event

Speaker: Xiaoming Zhang (Lawrence Berkeley National Lab. (US))

Slides QM2014_XiaomingZhang.pdf

15:40 Quantifying jet modification as a function of energy lost and jet mass depletion

Jet modification measurements to date are carried out by comparing a surviving jet, exiting a dense medium, with a vacuum (unmodified) jet at the same energy. We propose an extension to classify jet modification in heavy-ion collisions by also including the jet mass. The mass of a jet, as measured by jet reconstruction algorithms, is intimately connected to the jet's virtuality (or scale), which in turn has a considerable effect on such observables as the fragmentation function and jet shape observables. The leading hard parton, propagating through a dense medium tends to experience substantial virtuality (or mass) depletion along with energy loss, and thus accurate comparisons between surviving jets and jets produced in p-p collisions should take these effects into account. Using the event generator PYTHIA, we show the close relationship between the actual jet mass and that after applying a jet reconstruction algorithm. Using the in-medium event generator MATTER++, we demonstrate the clear difference between the mass of a surviving parton exiting a dense medium and a parton with a similar energy formed in a hard p-p event. Effects of this difference in jet mass on the ratio of fragmentation functions and jet shapes are also calculated.

Speaker: Abhijit Majumder (Wayne state university)

Slides majumder_parallel_may_21.pdf

14:20 → 16:00 Heavy flavor: 5

Convener: Johannes Peter Wessels (Westfaelische Wilhelms-Universitaet Muenster (DE))

announcement QM2014_announcement_Wed.pdf

14:20 J/$\psi$ production in p-Pb collisions with ALICE at the LHC

The study of charmonium production, bound states of c and $\bar{c}$ quarks, is an intense research activity, both experimentally and theoretically. The peculiar properties of some of the charmonium states, like their small size (< 1 fm) and strong binding energy (several hundred MeV), make them ideal probes of the strongly interacting matter, the so-called Quark-Gluon Plasma (QGP), produced in high-energy heavy-ion collisions. ALICE is dedicated to the study of QGP properties in heavy-ion collisions at the LHC. A suppression of the J/$\psi$ has been found in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV, with respect to the J/$\psi$ measured in pp collisions at the same center-of-mass energy. At the beginning of 2013, p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV have been studied at the LHC, in order to measure the effects related to cold nuclear matter, which, for charmonia, include gluon shadowing (or gluon saturation), energy loss and nuclear absorption. The study of these effects in p-Pb collisions is important in order to be able to disentangle hot and cold nuclear matter effects in Pb-Pb collisions. The obtained results on the J/$\psi$ production and nuclear modification factor as a function of rapidity or transverse momentum in p-Pb collisions, will be presented and compared to theoretical models. The rapidity ranges considered will include forward and backward rapidity (dimuon decay channel) and mid rapidity (dielectron decay channel). Likewise, a discussion on the forward-to-backward ratios will be held. First results on the dependence of the J/$\psi$ yields and its mean transverse momentum on the charged particle multiplicity will be also presented and discussed.

Speaker: Javier Martin Blanco (Laboratoire de Physique Subatomique et des Technologies Associe)

Slides JPsiProductionInpPbALICE.pdf

14:40 Z Boson Production in p+Pb Collisions measured by the ATLAS Experiment

The measurement of Z bosons in heavy ion collisions is an excellent tool for probing the nucleus at the partonic level. The inclusive yield provides a stringent test of binary collision scaling. Recent ATLAS results demonstrate such scaling in Pb+Pb collisions. The 2013 p+Pb physics run at the LHC providing more than 30 $nb^-1$ of collisions at an energy of $\sqrt{s_{NN}}$ = 5.02 TeV has made a detailed study of Z boson production in proton+nucleus interactions possible for the first time. These data may confirm binary scaling in the p-Pb system and help clarify the present ambiguity of centrality classifications in proton+nucleus collisions. Further, the momentum and rapidity differential yields of Z bosons allow the detection of any modification of the initial state present in such collisions.

Speaker: Zvi Citron (Weizmann Institute of Science (IL))

Slides quarkmatter.pdf

15:00 The fate of the weakly bound $\psi'$ in $p$$+$$p$, $d$$+$Au, A$+$A collisions

We present new results of a completed analysis from PHENIX of $\psi'$ modification at midrapidity in 200~GeV $d$$+$Au collisions. Strong differential suppression of the $\psi'$ relative to the $J/\psi$ is observed. This has also been reported recently by ALICE at forward and backward rapidity in 5.0~TeV $p$$+$Pb collisions. In all cases the differential suppression is too strong to be explained by nuclear breakup effects, due to the short nuclear crossing times. Given the observation of long range correlations in $p(d)$$+$A collisions at LHC and RHIC, consistent with hot matter effects, these observations raise very interesting questions about the mechanism of $\psi'$ suppression when it is produced in a nuclear target. In 2012, the PHENIX Collaboration installed the FVTX, a Silicon Tracker that precisely measures the pair opening angle prior to any multiple scattering in the muon arm absorber and thus provides an improved dimuon mass resolution. The FVTX also allows the $\psi'$ to be separated from the $J/\psi$ at forward and backward rapidity. During the 2012 data taking run, the PHENIX Collaboration collected a high statistics data sample of $p$$+$$p$ and Cu$+$Au collisions. We present new results on the $\psi'$ from this dataset.

Speaker: J. Matthew Durham (Los Alamos National Laboratory)

Slides Durham_QM14.pdf Durham_QM14.pptx

15:20 Inclusive $\psi$(2S) production at forward rapidity in p-Pb collisions with ALICE at the LHC

Charmonium states play a relevant role as probes of the phase transition between hadronic and deconfined matter. According to the color-screening model, the in-medium dissociation probability of such states should provide an estimate of the initial temperature. In nucleus-nucleus collisions, the more loosely bound excited states, as the $\psi(2{\rm S})$, are expected to melt at lower temperatures than the ground state (J/$\psi$). In proton-nucleus collisions at LHC energies, the charmonium formation time is larger than the time spent by the ccbar pair traversing the nucleus. Therefore, the cold nuclear matter is expected to affect in a rather similar way the J/$\psi$ and $\psi(2{\rm S})$. ALICE results on the inclusive $\psi(2{\rm S})$ production at forward rapidities ($2.5 < y < 4$), will be presented. Final results on the $\psi(2{\rm S})$/J/$\psi$ ratio in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV will be shown and compared to the corresponding pp measurement. Results on the $\psi(2{\rm S})$ production in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be also discussed. We observe an unexpected suppression of the $\psi(2{\rm S})$ yield, with respect to the J/$\psi$ one, which is difficult to reconcile with the presence of cold nuclear matter effects alone. To provide further insight on this observation, a differential study of the $\psi(2{\rm S})$ suppression, as a function of transverse momentum and centrality will be presented. Finally, ALICE $\psi(2{\rm S})$ results will be compared with theoretical models and with results by other experiments.

Speaker: Roberta Arnaldi (Universita e INFN (IT))

Slides QM2014_Arnaldi.pdf QM2014_Arnaldi.pptx

15:40 Towards continuum results of the heavy quark momentum diffusion coefficient

Among quantities playing a central role in the theoretical interpretation of heavy ion collision experiments at RHIC and LHC are so-called transport coefficients. Out of those heavy quark diffusion coefficents play an important role e.g. for the analysis of the quenching of jets containing $c$ or $b$ quarks ($D$ or $B$ mesons) as observed at RHIC and LHC. We report on a lattice investigation of heavy quark momentum diffusion within pure SU(3) plasma above the deconfinement transition, with the quarks treated to leading order in the heavy mass expansion. We measure the relevant "colour-electric" Euclidean correlator and based on several lattice spacings perform the continuum extrapolation. This extends our previous study [1,2] progressing towards a removal of lattice artifacts and a physical interpretation of the results. We find that the correlation function clearly exceeds its perturbative counterpart which suggests that at temperatures just above the critical one, non-perturbative interactions felt by the heavy quarks are stronger than within the weak-coupling expansion. Our results will be compared to heavy quark diffusion coefficients [3] obtained from charmonium vector correlation functions. [1] A. Francis, O. Kaczmarek, M. Laine, M. Müller, T. Neuhaus and H. Ohno, "Towards the continuum limit in transport coefficient computations", arXiv:1311.3759. [2] A. Francis, O. Kaczmarek, M. Laine and J. Langelage, "Towards a non-perturbative measurement of the heavy quark momentum diffusion coefficient", arXiv:1109.3941. [3] H.T. Ding, A. Francis, O. Kaczmarek, F. Karsch, H. Satz and W. Soeldner, "Charmonium properties in hot quenched lattice QCD", Phys.Rev.D86 (2012) 014509, arXiv:1204.4945.

Speaker: Dr Olaf Kaczmarek (University of Bielefeld)

Slides QM_2014.pdf

16:00 → 16:30 Coffee break

16:30 → 18:30 Poster session

Poster session with pretzels, beer, wine, and soft drinks

16:30 $\omega$(782) and $\phi$(1020) Meson Production in the Dielectron Channel in pp Collisions at $\sqrt{s}$ = 7 TeV with ALICE

Low-mass dielectrons are an important experimental tool to investigate the properties of the hot and dense medium created in ultrarelativistic heavy-ion collisions. Electrons do not interact strongly, therefore they provide information from all stages of the collision. In particular, a possible restoration of chiral symmetry in the hot and dense medium can be probed with dielectron decays of short-lived hadrons such as $\omega$(782) and $\phi$(1020) mesons, where pp collisions are used as medium-free reference. Furthermore, pp collisions are interesting by themselves to investigate particle production at LHC energies. In this poster, the status of a measurement of $\omega$(782) and $\phi$(1020) meson production in the $e^{+}e^{-}$- decay channel in pp collisions at $\sqrt{s}$ = 7 TeV with ALICE is presented. The results are compared to measurements in hadronic and $\mu^{+}\mu^{-}$- decay channels.

Speaker: Mahmut Ozdemir (Johann-Wolfgang-Goethe Univ. (DE))

Poster QM2014_poster_Ozdemir.pdf

16:30 $\phi$-meson production in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV measured with ALICE at the LHC

Particle production in p-Pb collisions, in contrast to pp, is expected to be sensitive to nuclear effects in the initial state. The role of the initial and final state effects can be understood from the measurement of identified particle spectra. One of the key observables to characterize the hot and dense matter produced in high-energy collisions is strangeness production. Here we will present the results on transverse momentum spectra ($p_{\rm T}$)) and integrated yield of $\phi$-mesons from p-Pb, $\sqrt{s_{\rm NN}}$ = 5.02 TeV recorded with the ALICE detector at LHC. The results will be discussed as a function of multiplicity classes.

Speaker: Ajay Kumar Dash (Universidade Estadual de Campinas (BR))

Poster PhipPbPosterQM2014V4.pdf

16:30 $\pi^0$ production in $\sqrt{s_{NN}}$=200 GeV Cu+Au Collisions at PHENIX

Cu+Au collisions at RHIC generate asymmetric initial geometries and densities in both azimuth and rapidity. High $p_T$ $\pi^0$s produced in $\sqrt{s_{NN}}$ = 200 GeV Cu+Au collisions provide new environments to study parton energy loss in the Quark Gluon Plasma. including very central events where the Cu nucleus is enveloped by the Au nucleus. By measuring $\pi^0$ yields in $\phi$ relative to the reaction plane, we can probe different core-corona regions in these very central events and study the path length dependence of energy loss in various lopsided initial geometries. PHENIX has observed the suppression of $\pi^0$s with respect to reaction plane in $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions and found it consistent with a cubic path length dependence suggesting a non-perturbative energy loss model applies. The unique collision geometries available in Cu+Au provide new settings to explore and possibly confirm this path length dependence. The status of the Cu+Au $\pi^0$ analysis will be presented.

Speaker: Sarah Campbell (Iowa State University)

Poster QMPoster2014_Pi0CuAu.pdf

16:30 $\psi$(2S) signal extraction in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC

Quarkonium states are important probes to investigate the properties of strongly interacting matter created in ultrarelativistic heavy-ion collisions and to confirm the presence of Quark-Gluon Plasma (QGP). A significant contribution to the observed suppression can also come from cold nuclear matter effects, which can be studied in proton-nucleus collisions. The $\psi(2{\rm S})$ production is studied in pp, p-Pb and Pb-Pb collisions at LHC energies using the ALICE detector, down to zero transverse momentum, in the dimuon decay channel and in the laboratory rapidity range $2.5 < y < 4$. The statistics is limited, with S/B ratios $\leq$ 0.2 (in pp collisions). In this situation, the extraction of the signal from the dimuon invariant mass distribution becomes very delicate, especially when performing differential analyses (e.g., vs. transverse momentum or rapidity). Therefore, the robustness of the $\psi(2{\rm S})$ signal extraction procedure is crucial to extract final physics results. Several approaches have been investigated, and details on the techniques adopted in the different collision systems will be presented.

Speaker: Marco Leoncino (University of Turin and INFN (IT))

Poster Poster_Leoncino_QM14.pdf

16:30 $\rm W^{\pm}$ boson production measurements in p-Pb collisions with ALICE at the LHC

At the LHC, electroweak boson production measurements in p-Pb and Pb-Pb collisions are possible thanks to the availability of higher centre of mass energies as well as higher luminosities with respect to other ion accelerator facilities. From a theoretical point of view, electroweak boson production can be considered to be well understood. $\rm Z^{0}$ and $\rm W^{\pm}$ bosons are produced in initial hard-scattering processes of partons and are not expected to interact with a strongly interacting medium. Therefore, measurements of electroweak bosons in proton-nucleus and nucleus-nucleus collisions represent a standard candle to check the validity of binary scaling and can provide important constraints to the nuclear parton distribution functions. In addition, such measurements could represent an ideal test-bench for luminosity measurements and detector performance studies. ALICE is the experiment at the LHC designed to investigate the properties of strongly-interacting matter formed in high-energy heavy-ion collisions. At forward rapidities, ALICE is equipped with a muon spectrometer that allows measurements of dimuon decays of quarkonia, muons from heavy-flavour hadron decays and also $\rm W^{\pm}$ bosons in the muon decay channel. Recent results on the $\rm W^{\pm}$ boson measurement at forward and backward rapidities, with respect to the direction of the proton beam, in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be presented.

Speaker: Francesco Bossu (iThemba Lab. for Accel. Based Sci. (ZA))

Slides bossuQM2014_poster.pdf

16:30 $\Sigma^0$ and $\overline{\Sigma}^0$ Baryon Production in pp Collisions at $\sqrt{s}$ = 7 TeV with ALICE at the LHC

Hyperon production in heavy-ion collisions is a very precious probe to study the properties of the hot dense matter, as it is sensitive to strangeness enhancement, chiral symmetry restoration and parton energy loss. Moreover, it allows to further constrain the chemical freeze-out parameters based on statistical models. The measurement of the full set of hyperons allows to discriminate prompt and decay hyperons, e.g. prompt $\Lambda$ and one from $\Sigma^0$ decay. The ALICE detector provides a unique capability to study the electromagnetic decay of $\Sigma^0$($\overline{\Sigma}^0$) baryon due to the possibility to measure the low energy photons. The status of the first observation of $\Sigma^0$ and $\overline{\Sigma}^0$(1192 MeV) baryon in pp collisions at $\sqrt{s} = 7$ TeV by ALICE at the LHC is presented. The $\Sigma^0 \to \Lambda + \gamma$ ($\overline{\Sigma}^0 \to \overline{\Lambda} + \gamma$) signal (branching is 100%) is reconstructed through an invariant mass analysis: the decay $\Lambda \to {\rm p} + \pi^-$ ($\overline{\Lambda} \to \overline{\rm p} + \pi^+$) is detected in the central tracking system of ALICE, while the photon is reconstructed via its conversion. The peak position is in agreement with the PDG data and its width is consistent with the results of Monte Carlo simulation. The $\Sigma^0$ ($\overline{\Sigma}^0$) baryon is measured in the transverse momentum range between 1 and 10 GeV/$c$. In addition, an invariant mass peak is reconstructed with the photon detected in the ALICE PHOS calorimeter.

Speaker: Alexander Borissov (Pusan National University (KR))

Slides Borissov-QM14-sigma0-20may14.pdf

16:30 $E_T$ distributions in p+p, d+Au and Au+Au at $\sqrt{s_{NN}}=200$ GeV and analysis based on Constituent-Quark-Participants

Measurements of mid-rapidity $dE_T/d\eta$ distributions in p+p, d+Au and Au+Au at $\sqrt{s_{NN}}=200$ GeV by PHENIX at RHIC are presented and analyzed in terms of the number of Constituent-Quark participants, $N_{\rm qp}$. This provides a physical way to introduce fluctuations in Glauber Model calculations of p+p collisions, since the spatial distribution of each of the three constituent quarks in a nucleon is generated according to the measured charge distribution of the proton. It had been noted previously that $dN_{\rm ch}/d\eta$ at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV as a function of centrality is not simply proportional to the number of nucleon participants, $N_{\rm part}$, (the Wounded Nucleon Model, WNM) but is linearly proportional to the number of constituent-quark participants, $N_{\rm qp}$, (the NQP model). For symmetric systems, the NQP model is identical to the Additive Quark Model (AQM) used in the 1980's, to explain a similar disagreement of $dE_T/d\eta$ distributions with the Wounded Nucleon Model in $\alpha+\alpha$ relative to p+p collisions at $\sqrt{s_{NN}}=31$ GeV at the CERN-ISR. However, the AQM and NQP models differ for the case of asymmetric systems such as d+Au, where the AQM, which is a color-string model, is effectively proportional only to the number quark-participants in the projectile. The present d+Au data clearly reject the AQM model in favor of the NQP, which is also in excellent agreement with the Au+Au data. The NQP model also explains why the additional contribution proportional the number of binary-collisions, $N_{\rm coll}$, added to $N_{\rm part}$ to parametrize the centrality-dependence of A+A collisions works, but does not imply a hard-scattering component in $E_T$ distributions and thus is no longer in disagreement with lessons learned from measurements of $E_T$ distributions in p+p(${\bar{\rm p}}$) collisions at the CERN SpS, ISR and SpS-Collider.

Speaker: Michael Tannenbaum (Brookhaven National Laboratory (US))

16:30 $J/\psi$ in pPb collisions with CMS

Charmonia in nucleus-nucleus (A-A) collisions are an important probe to study for understanding the deconfinement in heavy ion collisions at LHC energies. The measurement in proton-lead (p-A) collisions of prompt and non-prompt $J/\psi$ production enables us to investigate nuclear matter effects and therefore, provides a new input to examine the hot-medium effects in A-A collisions, which are still not fully understood. Using CMS, the transverse momentum and rapidity differential cross-sections, and forward to backward ratios of prompt and non-prompt $J/\psi$ in pPb collisions at center of mass energy per nucleon pair = 5.02 TeV will be presented. The dependence of forward to backward ratios with respect to the event characteristics will also be shown.

Speaker: Songkyo Lee (Korea University (KR))

Slides 20140520_songkyo_QM_v4.pdf

16:30 $J/\psi$ production in minimum bias U+U collisions at $\sqrt{s_{NN}}=193$ GeV in the STAR experiment

Suppression of quarkonia production in high energy nuclear collisions relative to proton-proton collisions, due to color screening of the quark-antiquark potential, has been predicted to be a sensitive indicator of the temperature of the created QGP. However, initial state cold nuclear matter effects, production via recombination of quark-antiquark pairs in the QGP and dissociation in hadronic phase could also alter the expected suppression picture. Systematic measurements of the quarkonia production in different colliding systems are hence crucial for disentangling relative contributions of these effects. At the STAR experiment we can utilize collisions of uranium nuclei to further study the quarkonia suppression pattern. Since the uranium nuclei are non-spherical, we are able to reach higher energy densities in the most central U+U collision compared to Au+Au collisions. In this poster, we will present the transverse momentum spectrum (0<$p_{\rm T}$<6 GeV/c) and nuclear modification factor of $J/\psi$ production, reconstructed at midrapidity via di-electron decay channel, in minimum bias U+U collisions at $\sqrt{s_{NN}}=193$ GeV in the STAR experiment.

Speaker: Ota Kukral (Czech Technical University, Prague)

Poster Kukral_QM2014.pdf

16:30 $K^{\ast}$(892)$^0$ resonance production with the ALICE experiment at the LHC

Short lived resonances are good probes to study the properties of strongly interacting matter produced in high energy heavy ion collisions. In particular, the resonance ${\rm K^{\ast 0}}$ is important because of its very short lifetime which is comparable to that of the fireball. The decay daughters are expected to undergo re-scattering and re-generation processes, which could modify the characteristic properties of ${\rm K^{\ast 0}}$ such as its mass, width and yield at low transverse momentum ($p_{\mathrm{T}}$). In addition, the yield of ${\rm K}^{\ast 0}$ at high ($p_{\mathrm{T}}$) may be suppressed in Pb-Pb relative to pp collisions due to the effect of the hot and dense medium formation. We report the measurement of the ${\rm K}^{\ast 0}$ resonance in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV and pp collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV via its hadronic decay channel $({\rm K}^{\ast 0}) (\overline{\rm K}^{\ast 0}) \rightarrow {\rm K}^{\pm}({\rm K}^{-}\pi^{+}) )$ with the ALICE detector. The centrality dependence of the mass, width, and yield of ${\rm K}^{\ast 0}$ in Pb-Pb collisions is compared to pp results to investigate the role of re-scattering and re-generation. The nuclear modification factor ($R_{\rm CP}$ and $R_{\rm AA}$) will be presented to study the effect of parton energy loss on ${\rm K}^{\ast 0}$ production and compared with other hadrons to understand the effect of baryon-meson separation.

Speaker: Kishora Nayak (National Institute of Science Education and Research (IN))

Transparents QM2014_HighpT_KStarPoster_v2.pdf

16:30 ${\rm D^0}$ meson production measurement in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE

The study of D mesons in proton-nucleus collisions provides insight into the role of cold nuclear matter effects in charm production, such as the modification of parton densities in nuclei and initial-state multiple partonic scattering. The observed modification of the D-meson transverse momentum distributions in central Pb-Pb with respect to pp collisions has been confirmed as due to hot nuclear matter effects, accessing the effects of cold nuclear matter via p-Pb collisions. ALICE collected data at $\sqrt{s_{\rm NN}}=5.02~\mathrm{TeV}$ during the 2013 LHC p-Pb run. ${\rm D}^0 \to {\rm K}^- \pi^+$ decays and their charge conjugates were reconstructed in the central rapidity region $|y_{{\rm lab}}|<0.8$. The ${\rm D^0}$ production cross section will be presented as a function of transverse momentum and rapidity. The nuclear modification factor in minimum-bias p-Pb collisions will be presented as well and compared with theoretical predictions including nuclear shadowing or saturation effects. Finally, the dependence of ${\rm D^0}$ production on the multiplicity of charged particles produced in the collision will be discussed.

Speaker: Andrea Festanti (Universita e INFN (IT))

Slides D0inpPb_AFestanti_QM2014.pdf

16:30 ${\rm D}^{+}$-meson reconstruction in pp collisions at $\sqrt{s}$ = 8 TeV with the ALICE detector

Heavy quarks (charm and beauty) are a powerful probe to investigate the properties of the medium created in heavy-ion collisions. Due to their large mass, heavy quarks are produced as a result of partonic scattering processes with large momentum transfer, occurring in the early stages of the collisions. The produced heavy quarks travel through the medium, experiencing all the stages of its evolution and finally they hadronize inside or outside the medium. The measurement of the charm production cross section in pp collisions provides an interesting insight in QCD processes and the necessary reference for heavy-ion studies. ALICE (A Large Ion Collider Experiment) is an experiment at the Large Hadron Collider (LHC) designed to carry out comprehensive measurements of the particles produced in high energy nucleus-nucleus collisions, in order to study QCD matter at high temperature and energy density and the transition between confined matter and the Quark-Gluon Plasma (QGP). D mesons are reconstructed through their hadronic decay channels. The detectors used for the D-meson reconstruction and selection are: the Inner Tracking System (ITS), the Time Projection Chamber (TPC) and the Time-of-Flight (TOF). In addition the Electromagnetic Calorimeter (EMCal) was used, with energy threshold ranging from 1.5 to 2 GeV, to trigger on events with a high energy particle, which allows us to have a data sample enriched of events with heavy flavours. We present the analysis status of the D$^{+}$-meson production in the data sample of pp collisions at $\sqrt{s}$= 8 TeV collected in 2012. D$^{+}$ mesons are reconstructed in the hadronic decay channel D$^{+} \rightarrow {\rm K}^{-}\pi^{+}\pi^{+}$. We focus on the studies of the D$^{+}$ signals obtained from the invariant mass distributions of triplets of tracks originating from secondary vertices displaced from the interaction point and on the performance of the EMCal trigger.

Speaker: Ankita Sharma (University of Jammu (IN))

Slides 2014-May-18-conferencefile-Ankita_QM_2014.pdf

16:30 A Fixed-Target Program for STAR: Extending the Low Energy Reach of the RHIC Beam Energy Scan

The RHIC Beam Energy Scan (BES) was proposed to search for the possible critical point and to study the nature of the phase transition between hadronic and partonic matter. Data from the NA49 experiment at CERN had suggested the onset of deconfinement at a collision energy of 7.7 GeV [1]. Though RHIC has not demonstrated sufficient luminosity to access collisions below 7.7 GeV in collider mode, collisions between beam nuclei and a gold target will allow STAR to study Au+Au collisions at center-of-mass energies of 3.0, 3.5, 4.0, and 4.5 GeV during the BES phase II. A proof-of-principle study, using collisions between beam halo nuclei and the aluminum beam pipe (runs in 2011 and 2012), has been investigated to demonstrate the feasibility of extracting physics from fixed-target collisions at center-of-mass energies below 7.7 GeV. Performance results from this proof-of-principle study will be presented. The gold target was installed for trigger tests in run 14. The first results of these tests will be presented. [1] Xi (Omega) production in Pb+Pb Collisions at 158 GeV/c, G. Odyniec for the NA49 Collaboration, J. Phys. G, 23, 1827 (1997)

Speaker: Brooke Haag (UC Davis)

Slides STARFixedTargetPosterQM_Haag_2014_v6.pdf STARFixedTargetPosterQM_Haag_2014_v6.pptx

16:30 A Muon Detection System for the CBM experiment at FAIR

A Muon detection system is under development for the CBM experiment at the upcoming FAIR facility at GSI. By measuring muon pairs from the decay of low-mass vector mesons and charmonium, the Muon Chamber system (MUCH) will substantially contribute to the exploration of the QCD phase diagram at large baryon chemical potentials. The research program includes the search for de-confinement and chiral phase transitions, and for new phases of strongly interacting matter. The MUCH subsystem is based on a novel concept of segmented absorbers with varying thickness and detector layers sandwiched between them. Detailed simulations have been performed to optimize the material, the thickness and the position of the absorbers, and the granularity of the detectors. The design goal is to simultaneously identify both high and low momentum muons over the full phase space. A combination of large size GEM chambers and straw tubes will form the tracking detector system in MUCH. The detectors will be read out in a self-triggered mode to handle unprecedented high interaction rates of 10 MHz. Several prototype detectors have been built and tested successfully with X-rays and particle beams using a self-triggering readout electronics. Results of the feasibility studies and of the detector development will be presented.

Speaker: Anand Kumar Dubey (Department of Atomic Energy (IN))

Slides QM2014_MUCH_poster.pdf

16:30 A new calculation of light quark jet energy loss using the AdS/CFT correspondence

Unlike heavy quarks, light quark energy loss in AdS/CFT is surprisingly dependent on both the string initial conditions and the very definition of the jet itself in the gravity theory. In order to more accurately model QCD jet energy loss in AdS/CFT, we more closely match the string initial conditions to those expected from pQCD and simultaneously propose a novel jet prescription in the dual theory. With the new jet prescription, light quark jet energy loss regains the “explosive,” late-time Bragg peak in both static and expanding plasmas. We incorporate the improved AdS/CFT results into a phenomenological energy loss model and compare our predictions to light meson suppression at RHIC and LHC.

Speaker: Razieh Morad (University of Cape Town)

Slides poster.pdf

16:30 A New Study of Parton Energy Loss Mechanisms in p+A Collisions at Fermilab E906 Experiment

Jet quenching in heavy ion collisions is considered to be one of the important tools to study the QGP properties at RHIC and LHC. However, at present there are several competing models to describe the jet energy loss processes in heavy ion collisions, and current heavy ion data cannot clearly discriminate between them, thus the interpretation of QGP data is very model dependent. High energy p+A collisions may provide control of various cold nuclear matter effects, and with the proper kinematics, provide a clear determination and calibration of various parton energy loss models, thereby helping to improve the calculations for A+A. Past efforts to extract the effects of parton energy loss in p+A resulted in a large uncertainty due to ambiguities from competing effects, such as parton shadowing. E906/SeaQuest is a new fixed-target dimuon experiment using 120 GeV proton beams from the Fermilab main injector. E906 measures J/Psi and Drell-Yan production in the dimuon channel in p+p and p+A collisions over a wide range of xF, and employs fixed targets of D, C, Fe, and W. The kinematic coverage is ideal for parton energy loss studies for 20~60 GeV “incoming” quarks, and shadowing effects are expected to be minimal. E906 had its first engineering run in early 2012 and successfully observed the J/Psi mass peak in the dimuon channel. E906 is currently taking high statistics data since the beginning of this year. We expect the new data will help clarify the nature of parton energy loss in the nuclear medium. In this talk, we will briefly review the latest progress in parton energy loss study in p(d)+A collisions and present the current status and the prospects from the E906/SeaQuest experiment at Fermilab.

Speaker: Dr Ming Liu (Los Alamos National Laboratory)

16:30 An Analytic Study of the Initial Energy Momentum Tensor in Nuclear Collisions

We present an analytic calculation of the initial classical gluon field in high energy collisions of nuclei. Our results are explicit expressions for the components of the event-averaged energy momentum tensor which are valid up yo times $\tau\sim1/Q_s$. In particular we will discuss the early time evolution of the energy density and longitudinal and transverse pressure, and compare to available numerical results. We then demonstrate how both a rapidity-odd and rapidity-even energy flow emerge naturally from the QCD analogues of Faraday's and Gauss' Law. We discuss their phenomenological consequences in terms of initial elliptic flow, global angular momentum and directed flow. We will also briefly mention how an event generator can be built based on these results.

Speaker: Rainer Fries (Texas A&M University)

Poster QM2014_Poster_Fries.pdf

16:30 An Electron Ion Collider (EIC) Detector Built Around the BaBar Magnet (ePHENIX)

As a particular realization of an electron ion collider (EIC), the eRHIC project envisions the addition of a high intensity polarized electron beam to the existing RHIC facility, providing $e$$+$$p$ and $e$$+$A collisions and enabling precision studies of the partonic structure of hadronic matter. To fully exploit the physics potential of eRHIC, the PHENIX Collaboration is proposing a detector built upon sPHENIX, a planned upgrade of the current PHENIX experiment. This new detector, ePHENIX, uses the sPHENIX superconducting solenoid and barrel calorimetry and adds to this foundation precision tracking, particle-identification and calorimetry in the barrel, electron-going and hadron-going directions, opening a broad range of exciting EIC physics measurements (see \url{http://arxiv.org/abs/1402.1209}). We give an overview of ePHENIX detector design and discuss its broad capabilities for both nucleon structure imaging and high density nuclear matter studies.

Speaker: David Morrison (BNL)

16:30 Analysis of D-h and D-e angular correlations with ALICE, and perspectives for the upgrade

In collisions of lead nuclei at the Large Hadron Collider (LHC) at CERN, a state of matter called Quark-Gluon Plasma (QGP) is predicted to be formed, where quarks and gluons are no longer confined into hadrons. Heavy-flavour quarks, i.e., charm and beauty, are effective probes for studying the QGP, as their relatively large mass limits their production predominantly, if not exclusively, to hard scattering processes in the very first moments of the collisions, before the QGP formation. As the quarks propagate through the hot and dense medium created in the Pb-Pb collisions they interact with the medium and lose energy via elastic collisions and gluon radiation. The study of the modification of the angular correlation between D mesons and charged hadrons, as well as the correlation between D mesons and electrons from heavy-flavour hadron decays in Pb-Pb collisions with respect to pp and p-Pb collisions can provide relevant information on the energy-loss mechanism. This applies in particular to the dependence of the correlation on the path length traversed by the charm quark in the medium, and to possible medium modifications of charm-quark fragmentation and hadronisation. In pp collisions, these measurements can be sensitive to the different production processes of heavy-flavour quarks, e.g., pair production vs. gluon splitting. In this poster, the results of the analysis of azimuthal correlations between D mesons and charged hadrons in pp collisions at $\sqrt{s}=7$ TeV and p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be presented. In addition, the prospects for measuring correlations of D mesons and electrons from heavy-flavour hadron decays will be discussed. The performance expected after the upgrade of the ALICE detector during the long shutdown in 2018 will also be shown.

Speaker: Per-Ivar Lonne (University of Bergen (NO))

Poster Loenne.pdf

16:30 Anisotropic flows and the shear viscosity of the QGP within a transport approach with initial state fluctuations.

We discuss the build up of elliptic flow and high order harmonics $v_n$ within a transport approach at fixed shear viscosity to entropy density ratio and with initial state fluctuations. We show, exploring the $T$ dependence of $\eta/s$, that a study of $v_n$ in a wide $p_T$ range allows to understand the difference behind the collective flows at LHC respect to RHIC. Furthermore we present novel results about the impact of $\eta/s$ on the correlations between the initial space eccentricity $\epsilon_n$ and the final anisotropic flows $v_n$. In particular we study the effect of a temperature dependent $\eta/s$ at different beam energies from RHIC for $Au+Au$ at $\sqrt{s}= 62.4, 200$ GeV to LHC energies for $Pb+Pb$ at $\sqrt{s}= 2.76$ TeV. We find that for the different beam energies considered the suppression of the elliptic flow due to the viscosity of the medium has different contaminations coming from the hadronic or QGP phase depending on the average energy of the system. References [1] S. Plumari, V. Greco and L.P. Csernai, arXiv:1304.6566 [nucl-th]. [2] M. Ruggieri, F. Scardina, S. Plumari and V. Greco, Phys.Lett. B727 (2013) 177-181. [3] S. Plumari, A. Puglisi, F. Scardina and V. Greco, Phys.Rev. C86 (2012) 054902.

Speakers: Salvatore Plumari (University of Catania (Italy)), Vincenzo Greco (University of Catania)

Poster PLUMARI_POSTER_QM2014.pdf

16:30 Applications of Chaos Many-Bode Engine for the analysis of relativistic nuclear collisions at 200 A GeV/c

Recently, we proposed a C# code, namely Chaos Many-Body Engine [1,2], for chaos analysis of relativistic many-body systems with reactions. Preliminary tests using a simplified relativistic nuclear collisions model resulted in some encouraging results for describing global physical quantities obtained in C-C collisions at 4.5 A GeV/c in experiments performed at JINR Synchrophasotron (SKM 200 Collaboration) [3]. The code allows introduction of some additional interactions among particles in the participant region, thus improving the description of the particle production in nucleus-nucleus collisions. The code permits, also, the investigation of time evolution of the collisions, from the initial moment up to the freeze-out. The time evolution step can be below 0,1 Fm/c. Using the possibilities for code development, we try to improve the agreement between our code and existing experimental results. Two collisions will be discussed, namely Cu-Cu at maximum BNL energy, and d-Au at the same energy. The code predictions and experimental results improve the agreement when we include more collisions and particle production mechanisms in the participant region. The time evolution of the fireball is well reflected by our code (Fig.1), for an evolution time between 0,1 and 200 Fm/c. For the time evolution, code hypotheses do not cover all aspects and some behaviors of the experimental results are not completely described. Work is in progress for improving the agreement with the experimental results. [1]. I.V.Grossu et al. – Comp.Phys.Comm. 179(1-3)(2008)199, 181(8)(2010)1464, 184(4)(2013)1346 [2]. I.V.Grossu et al. – accepted for publication in Comp.Phys.Comm. 185(2014) [3]. I.V.Grossu et al. – Annual Scientific Session of the Faculty of Physics, University of Bucharest, 2013

Speaker: Prof. Alexandru Jipa (Atomic and Nuclear Physics Chair, Faculty of Physics, University of Bucharest, Romania)

16:30 Approach to equilibrium: Universal properties in expanding gauge and scalar field theories

We show simulation results for longitudinally expanding gauge and scalar field theories as they approach thermal equilibrium. Most remarkably, we find a common nonthermal attractor solution in a characteristic momentum regime. As a consequence, important aspects of the evolution towards equilibrium turn out to be insensitive to the details of the underlying theory.

Speaker: Kirill Boguslavski (Heidelberg University)

Poster QM2014_Kirill_Poster.pdf

16:30 Azimuthal asymmetries in high-energy collisions of protons with holographic shockwaves

Large azimuthal quadrupole and octupole asymmetries have recently been found in p+Pb collisions at the LHC. We argue that these might arise from a projectile dipole scattering off randomly shaped intrinsic fluctuations in the target with a size on the order of the dipole. Generic energy-momentum fluctuations generate comparable asymmetries for all multipole moments vn. The holographic description of this process involves the calculation of a light-like Wilson loop in the background of a non-uniform holographic shockwave in the presence of a Neveu-Schwarz 2-form.

Speaker: Jorge Noronha (University of Sao Paulo)

16:30 Azimuthally-anisotropic photon spectrum induced by chiral anomaly in strong magnetic fields

It has been known for a long time that neutral-pions dominantly decay into two photons, which was subsequently understood on a robust theoretical basis after the discovery of chiral anomaly. A theorem shown in a seminal paper by Adler and Bardeen [1] indicates that a neutral pion is coupled to only two-photon states without couplings to other multi-photon states. When chiral anomaly is tied to extremely strong magnetic fields created in ultrarelativistic heavy-ion collisions [2], we find that transition between a neutral pion and a photon becomes possible with one of the two photons replaced by an external magnetic field. The theorem allows us to obtain the transition amplitude governed by chiral anomaly without theoretical ambiguities. We discuss attainable signatures of the anomaly-induced transition between neutral pions and photons in RHIC and LHC experiments. Although the magnetic fields persist for $1\, {\rm fm}/{\it c}$ or even shorter duration after the heavy ion collisions, we still find a photon source having much chance to interact with the magnetic field, that is, the prompt photon emitted just at the impacts of the collisions. While the prompt real photons propagate in the magnetic field, a part of the photons is converted into neutral pions, leaving an reduced amount of photons. Then, we show that the prompt photons to be measured in the experiments should have a negative $v_2$ and particular polarizations [3], since the transition amplitude is azimuthally anisotropic and depends on the photon polarizations due to a preferred orientation prescribed by the external magnetic fields. We propose that analyses on those observables should be performed in the future experiments, which makes the creation of the strong magnetic fields evident, while major attention has been conventionally paid to the total yield of prompt photons. We take into account the time dependence of the magnetic fields, and show the beam energy and impact parameter dependences of the photon's $v_2$ and polarizations. This work will provide impacts on elucidating formation of the prompt-photon spectrum as a penetrating probe from the very early stage, and thus shed light on an aspect of the early-time dynamics in the heavy-ion collisions. 1. S. Adler and W. Bardeen, Phys. Rev. 182 (1969) 1517-1536. 2. D. E. Kharzeev, L. D. McLerran, and H. J. Warringa, Nucl. Phys. A 803 (2008) 227-253; V. Skokov, A. Y. Illarionov and V. Toneev, Int. J. Mod. Phys. A 24 (2009) 5925-5932; A. Bzdak and V. Skokov, Phys. Lett. B 710 (2012) 171-174; W. T. Deng and X. G. Huang, Phys. Rev. C 85 (2012) 044907. 3. K. Hattori, K. Itakura and S. Ozaki, arXiv:1305.7224 [hep-ph].

Speaker: Dr Koichi Hattori (RIKEN)

16:30 Azimuthally-sensitive two-pion interferometry in U+U collisions at STAR

Collisions between uranium nuclei have been produced in the Relativistic Heavy Ion Collider and measured in the STAR detector. Due to the prolate deformation of the nuclei, fully overlapping U+U collisions offer the opportunity to produce highly anisotropic participant zones, similar in shape to mid-central Au+Au collisions, but with twice the size. The larger fireball should be characterized by a long time over which it collectively evolves from its non-trivial initial shape to its final one. The final-state anisotropy of zero-spectator collisions in *momentum* space ($v_n$) is under active study. We will present a preliminary analysis of the *coordinate*-space anisotropy, measured via azimuthally-sensitive two-pion interferometry ("HBT") of full-overlap collisions, performed differentially in the reduced flow parameter $q_{2}$ in U+U collisions at$\sqrt{s_{NN}}$ = 193 GeV.

Speaker: John Campbell (The Ohio State University)

16:30 Baryon-to-meson ratio of strange particles in near-side and away-side jets in pp collisions with ALICE using azimuthal correlations

Two-particle azimuthal correlations are an ideal tool to study high $p_{\rm T}$ parton fragmentation without full jet reconstruction. Enhancements of the azimuthal correlations are seen at $\Delta \varphi = 0$ and $\Delta \varphi = \pi$, corresponding to the near-side and away-side jets, respectively. We present correlations between charged leading particle and associated strange baryons ($\Lambda$) and mesons (${\rm K_s^0}$) in pp collisions at $\sqrt{s}$ = 7 TeV. Associated particle yields in near- and away-side jets, as well as in the underlying event, were extracted in different $p_{\rm T}$ intervals from 1 GeV/$c$ to 6 GeV/$c$. Extracted $\Lambda/{\rm K_s^0}$ in jets and the underlying event were compared to the inclusive $\Lambda/{\rm K_s^0}$ ratio and pQCD-inspired models.

Speaker: Sandun Pahula Hewage (University of Houston (US))

16:30 Beam Energy Dependency of Clan Multiplicity at RHIC

Negative binomial distribution has been widely used in describing the multiplicity distribution in high energy collisions. The parameters of a negative binomial distribution can be transformed to clan parameters, namely, the average number of clans and the average number of particles per clan (clan multiplicity) [1]. Clan parameters have been used to identify abnormalities due to a phase transition. In this talk, STAR's measurement of clan multiplicity will be presented for AuAu collisions at center-of-mass energies of 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV per nucleon-nucleon pair. The energy dependence will be studied for events from various centrality classes. The implications of these results to the search for possible signals of a phase transition and/or a critical point will be discussed. [1] A. Giovanni, L. Van Hove, Z. Phys. C30 391 (1986).

Speaker: Dr Aihong Tang (Brookhaven National Laboratory)

16:30 Beam energy scan using a 3+1D viscous hydro+cascade model

Following the BES program at BNL RHIC, we perform a similar collision energy scan using a 3+1D viscous hydrodynamics coupled to the UrQMD hadron cascade. We study how the collision energy affects the bulk observables: rapidity distributions and $m_T$-spectra of identified particles, elliptic flow, directed flow and HBT radii, including azimuthally-sensitive HBT. In our calculations we use an equation of state for finite baryon density and averaged or event-by-event initial conditions from UrQMD. We show that the final observables are sensitive to the initial state fluctuations and its granularity, as well as to the shear viscosity in the hydrodynamic stage. Fortunately the simultaneous reproduction of rapidity/$m_T$ distributions from NA49 and newer elliptic flow data from STAR can constrain both the granularity of the initial state and shear viscosity in hydrodynamic phase. We also explore the impact of different equations of state on final observables, and the possibility to discriminate between them.

Speaker: Dr Iurii Karpenko (Frankfurt Institute for Advanced Studies, Germany; Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine)

Poster QM14_2c.pdf

16:30 Bose-Einstein correlations with identified particles in CMS

Short range correlations of identified charged hadrons in pp ($\sqrt{s}$ = 0.9, 2.76, and 7 TeV), pPb ($\sqrt{s_{NN}}$ = 5.02 TeV), and peripheral PbPb collisions ($\sqrt{s_{NN}}$ = 2.76 TeV) are studied with the CMS detector at the LHC. Charged pions, kaons, and protons at low $p_T$ and in laboratory pseudorapidity $|\eta| < 1$ are identified via their energy loss in the silicon tracker. The two-particle correlation functions show effects of quantum statistics, Coulomb interaction, and also indicate the role of multi-body resonance decays and mini-jets. The characteristics of the one-, two-, and three-dimensional correlation functions are studied as a function of pair momentum and the charged-particle multiplicity of the event. The extracted radii are in the range 1-5 fm, reaching highest values for very high multiplicity pPb, also for similar multiplicity PbPb collisions, and decrease with increasing $k_{T}$. The dependence of radii on multiplicity and $k_{T}$ largely factorizes and appears to be insensitive to the type of the colliding system and center-of-mass energy.

Speaker: Ferenc Siklér (Wigner RCP, Budapest (HU))

Slides shortCorr_poster.pdf

16:30 Bottomonium at finite temperature from lattice QCD

I will present some recent results from the FASTSUM collaboration on the bottomonium spectrum at finite temperature from lattice QCD. From the calculation of the spectral functions using the maximum entropy method we confirm earlier findings on the survival of the ground state S wave states up to at least 2$T_c$ and observe further strong indications of the dissociation of the P wave ground states immediately in the deconfined phase. In this work we use ensembles with $N_f=2+1$ dynamical quarks and improved lattice parameters. The heavy quark is treated with a non-relativistic effective theory on the lattice and serves as a probe of the hot medium. We discuss the reconstruction of the spectral functions from the Euclidean correlation functions.

Speaker: Tim Harris (Trinity College, Dublin)

Poster qm2014_harris.pdf

16:30 Bottomonium melting from a stochastic potential

Understanding the suppression patterns of heavy Quarkonium promises valuable insight into the quark-gluon plasma created in relativistic heavy-ion collisions at RHIC and LHC. Here we present simulations of Bottomonium real-time evolution [1] in an idealized, i.e. static, QGP at high temperature, based on the open-quantum systems concept of stochastic potential [2]. If a heavy Quarkonium bound state is submerged in the QGP, it is subject to screening and scattering from the surrounding light partons. Effective field theory tells us that under such circumstances its correlation function obeys a Schrödinger equation with a complex potential V(r). We interpret the resulting loss of correlations with the initial state, i.e. the presence of Im[V], as decoherence, which is induced by the thermal fluctuations of the medium. To incorporate this phenomenon into the non-relativistic description, we use a purely real potential, whose values are stochastically varied at each time step by purely real noise. It is the spatial noise correlations that are then intimately related to Im[V]. Based on this setup, we discuss the intricate interplay between state mixing and thermal (de-)excitations, which governs the real-time evolution of Bottomonium vacuum initial states, as they propagate in the QGP. [1] A.R. arXiv:1312.3246 submitted to JHEP
[2] Y.Akamatsu and A.R. Phys.Rev. D85 (2012) 105011

Speaker: Alexander Rothkopf (H)

Slides PosterStochasticQQbar_v1.0.pdf

16:30 Causal hydrodynamic fluctuation and its implementation in full (3+1)-D dissipative hydrodynamic simulation

We formulate relativistic fluctuating hydrodynamics with causal hydrodynamic fluctuations and implement them into our dynamical model for more quantitative analysis of the transport coefficients of the matter created in heavy ion collisions. The hydrodynamic fluctuations are thermal fluctuations arising in the event-by-event hydrodynamic evoluation of the system, and its power spectrum is determined through the fluctuation-dissipation relation. While, the higher harmonics $v_n$ ($n>2$) are systematically observed in RHIC and LHC and attract a lot of theoretical and experimental interests. Initial state fluctuations turned out to be important to explain these higher harmonics through event-by-event hydrodynamic simulations. The event-by-event hydrodynamic fluctuation, although its average is locally zero, also has effects on the higher harmonics and other observables in the same manner as the initial fluctuations which vanish in the averaged picture of the initial condition. Recently, it is actively discussed to extract the shear viscosity from the experimental observables using hydrodynamic simulations with the initial fluctuations. The initial fluctuations are converted to observables through the response of the matter, which enables us to obtain information on the properties of the matter as well as on the initial state. But, the higher harmonics are created not only by initial state fluctuations, and the other sources of fluctuations such as the hydrodynamic fluctuation also play important roles. Therefore, to extract the quantitative properties of the quark-gluon plasma from experimental data, it is important to properly implement all the sources of fluctuations including hydrodynamic fluctuations in an integrated dynamical model with models of initial states, hydrodynamics of quark-gluon plasma and subsequent hadronic cascades. First, we formulate relativistic fluctuating hydrodynamics with the hydrodynamic fluctuation \[1\] in the context of the causal dissipative hydrodynamics which are commonly used in dynamical models for heavy-ion collisions. In causal dissipative hydrodynamics, the hydrodynamic fluctuation of the dissipative currents becomes colored noise due to the fluctuation-dissipation relation. But, interestingly, noise turns out to be always white in the differential form of the constitutive equations, which comes from general properties of the response function of the dissipative currents including causality and resulting constraints on the structure of the constitutive equations. Next, we implement the hydrodynamic fluctuations into our integrated dynamical model and investigate the behavior of the hydrodynamic fluctuations in heavy-ion collisions and discuss effects on experimental observables. The effect can be more significant in higher orders of the harmonics $v_n$, and in smaller systems such as peripheral collisions or central pA collisions. **References** \[1\] Koichi Murase, Tetsufumi Hirano, arXiv:1304.3243 [nucl-th] ![(2+1)-D example of hydrodynamic fluctuations][2] [2]: http://tkynt2.phys.s.u-tokyo.ac.jp/~murase/share/murase_qm2014f.gif "hydrodynamic fluctuations"

Speaker: Koichi Murase (The University of Tokyo)

Slides 20140520.murase_v4.pdf

16:30 Cavitation and bulk viscosity

It has been show that hydrodynamic models provide an effective, phenomenological description of the QGP. The framework of hydrodynamics allows the occurrence of interesting phenomena like cavitation. Cavitation, in general, is the phase change from the liquid to the gaseous phase caused by a pressure drop. First, one way of defining cavitation for relativistic hydrodynamics is presented. Afterwards, by using this previously defined concept, it is possible to constrain the maximum value of the bulk viscosity over entropy density $\zeta/s$, a value that is currently not easily accessible by other methods. Although bulk viscosity exists only in non-conformal fluids, this approach can be justified as a small perturbation to a conformal fluid setup. Numerical and analytical methods are discussed, and the results are compared with known cases.

Speaker: Mathis Habich (University of Colorado Boulder)

Poster Poster QM2014 Onset of cavitation in the quark--gluon plasma arXiv:1405.1978

16:30 Centrality and pseudorapidity dependence of dE$_T$/d$\eta$ in pPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with CMS

High energy proton lead collisions provide a unique tool to study the parton distribution function of nuclei at very low Bjorken x. The production of transverse energy at a given eta is sensitive to the gluon density in the nucleus, and by scanning over a very wide rapidity and centrality range, it is possible to glean information on the spatial and x dependence of the gluon density. The ratio of dE$_{T}$/deta at a given centrality range to the most central range for pPb collisions at center of mass energy per nucleon pair = 5.02 TeV is presented. The centrality dependence of this ratio depends strongly upon eta and also on the eta range used to define centrality. These results are compared to lower energy data and two Monte Carlo simulators, EPOS and AMPT, in order to provide insight into the nuclear wavefunction at low x.

Speaker: Christopher Ryan Edwards-Bruner (University of Kansas (US))

Slides QMPoster2014v2.pdf

16:30 Centrality Categorization for $R_{p(d)+A}$ in High-Energy Collisions

High energy proton- and deuteron-nucleus collisions provide an excellent tool for studying a wide array of physics effects, many of which are expected to have a significant dependence on the impact parameter of the collision, which is related to the collision centrality. We detail a method, employed by PHENIX, for determining centrality classes in $p(d)+A$ collisions via cuts on the produced charge particle multiplicity in the nucleus-going (-3.9<$\eta$<-3.0) direction. Using a Glauber Monte Carlo simulation we are able to map the centrality classes to geometric quantities of interest, along with corresponding systematic uncertainties. Within this framework we calculate the centrality bias-correction factors on the nuclear modification factor $R_{p(d)+A}$ due to correlations between a measured process and the multiplicity in the nucleus-going direction. These bias-correction factors are tested further using the HIJING MC generator, confirming that for $d+$Au collisions at $\sqrt{s_{NN}}=200$ GeV the corrections are small and vary by less than 5% (10%) for hadron production at midrapidty up to $p_{T}$=10(20) GeV/$c$. In contrast, we find that the bias correction factors for $p+$Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are an order of magnitude larger and exhibit a strong dependence on hadron $p_T$, which likely is due to the larger effect of multiparton interactions.

Speaker: Dr Darren McGlinchey (University of Colorado)

Slides McGlinchey_poster_QM2014.pdf

16:30 Centrality dependence of the J/$\psi$ production in p-Pb collisions with ALICE at the LHC

The study of proton-nucleus collision at LHC energies represents an important step in Quark-Gluon Plasma related studies, allowing a quantitative evaluation of cold nuclear matter effects on various observables. The ALICE Collaboration is carrying out a comprehensive study on charmonium production in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV in the dimuon decay channel. The analysis of the centrality dependence of the J/$\psi$ production is now in progress. Various centrality-related observables are being investigated, and their use in the charmonium analysis is being evaluated. In this poster, we will discuss the present status of the study of the centrality dependence of the J/$\psi$ production in p-Pb collisions, including an estimate of the $\langle p_{\rm} \rangle$ evolution with centrality.

Speaker: Igor Lakomov (Universite de Paris-Sud 11 (FR))

Poster QuarkMatter2014_Lakomov.pdf

16:30 Centrality Detector for Collider-based Heavy Ion Experiments

Parameters of the initial state of the heavy-ion (HI) interaction are commonly denoted by the term “centrality”. Centrality includes the impact parameter of the interaction, amount of interacting material and relative orientation of colliding nuclei. Unfortunately, none of these parameters can be directly measured. In all currently operating and planned HI experiments centrality is measured indirectly, using particles produced in the HI interactions, usually at high-rapidity. That requires assumptions about the high-rapidity particle production mechanisms that are not very well studied, and also requires a model relating produced particles to the initial state geometry, the Glauber model. These two assumptions lead to significant systematic uncertainties in centrality determination. Further, use of produced particles is affected by the correlations between the centrality determination rapidity and the rest of the detector coverage, where the physics measurements are done. This, in turn, requires additional corrections resulting in additional systematic uncertainties. Recent results from the LHC experiments reveal the importance of the long-range rapidity correlations in HI interactions. The proton-lead results also demonstrate that the Glauber model itself may require further adjustments. In collider-based HI experiments there is a unique possibility to measure centrality parameters by registering spectator fragments remaining from the collision on both sides. Spectator fragmentation mechanism is decoupled from particle production mechanism. This approach does not require Glauber model as spectators and participants are related via the total number of nucleons in the colliding species. Spectators continue flying along the direction of the colliding beams retaining practically unmodified longitudinal momentum, however their mass-to-charge ratio is typically lower than that of the colliding species. We propose a concept of the Centrality Detector, which measures masses of most of the fragments by measuring their deflection in the magnetic field of the collider elements and their charges. The field, and a set of detectors integrated in the structure of collider rings act as a very precise mass-spectrometer for such fragments. First calculations based on the DPMJet generator show that the Centrality Detector can provide better accuracy than currently used methods. Main factors affecting its performance will be discussed in the presentation.

Speaker: Alexander Milov (Weizmann Institute of Science (IL))

Slides centrality.pdf

16:30 Charge dependent elliptic flow from anomalous hydrodynamics

Anomaly-induced transport effects, like the chiral magnetic effect or the chiral separation effect, have recently attracted much attention. These effects represent the existence of dissipationless vector and axial currents along the magnetic field and are expected to occur in ultra-relativistic heavy-ion collisions. It has been pointed out that the coupling between the chiral magnetic effect and the chiral separation effect provokes a novel type of gapless collective excitation in the plasma, called chiral magnetic wave (CMW). The experimental search for anomaly-induced transports in heavy-ion collisions is now ongoing. Since the CMW leads to an electric charge quadrupole deformation in the quark-gluon plasma (QGP) created in heavy-ion collisions, the elliptic flow parameter $v_2$ would be charge-dependent, which can be considered as a signal of anomalous transports [1]. The STAR Collaboration observed such a charge dependent elliptic flow for pions $\Delta v_2 (\pi^\pm)$ [2]. This result seems to be consistent with the prediction from a simple model [1], in which propagation of non-interacting waves under spatially and temporally uniform temperature and homogeneous magnetic field is considered. However, since the QGP created in heavy-ion collisions is drastically expanding, it is necessary to describe the space-time evolution of the QGP together with that of electromagnetic fields in order to assess the contribution from anomalous transports. In this study, we numerically solve anomalous hydrodynamic equations and apply it to the dynamics of heavy-ion collisions [3]. We develop a numerical code which is applicable to the description of the QGP under arbitrary external electromagnetic fields. We describe the propagation of the CMW in the expanding QGP under spatially and temporally inhomogeneous external electromagnetic fields. We analyze the charge-dependent elliptic flow $v_2^\pm$ and discuss possible implications for experimental observations of anomalous transport effects. **References:** [1] Y. Burnier, D. E. Kharzeev, J. Liao, and H. -U. Yee, Phys. Rev. Lett. 107, 052303 (2011) [2] G. Wang [STAR Collaboration], Nucl. Phys. A904-905 2013, 248c (2013) [3] M.Hongo, Y. Hirono, T. Hirano, [arXiv: 1309.2823]

Speaker: Masaru Hongo (The University of Tokyo)

Poster hongo_QM2014_poster.pdf

16:30 Charge splitting of directed and elliptic flow in heavy ion collisions

We investigate the effect of the Coulomb field of the spectator matter on the directed and elliptic flow of charged pions. By means of a numerical Monte Carlo simulation, we find that the spectator charge induces sizeable values of directed flow. At beam and target rapidities, these can reach $v_1$=0.2 which is comparable to values reported by the WA98 collaboration in the corresponding kinematical range [1]. This effect is opposite for positive and negative pions, resulting in a *charge splitting of directed flow*. In the range of lower RHIC and SPS energies, the charge splitting extends down to midrapidity where our predicted values are in good agreement with very recent measurements reported by the STAR collaboration [2]. This effect appears to be strongly sensitive to the position of the pion formation zone with respect to the spectator system. Therefore, it provides *new, independent information* on the expansion of participant matter in the course of the collision. By comparing the results of our predictions with the STAR and WA98 data, we investigate the *geometrical features* characterizing pions at freeze-out as they appear from our study of electromagnetic effects. We discuss the possibility to use the spectator-induced electromagnetic interaction as a new source of information on the space-time evolution of particle production at high energies. Finally, for the first time, we present our new results on the *charge splitting of elliptic flow* which we discuss in the context of measurements reported by the STAR collaboration [3]. Additionally, we stress the complementarity of our study to the very recent analysis by Gursoy, Kharzeev and Rajagopal [4]. Most of this work was previously published in Ref. [5]. References: [1] H. Schlagheck (WA98 Collaboration), Nucl. Phys. A **663**, 725 (2000). [2] L. Adamczyk *et al.* (STAR Collaboration), arXiv:1401.3043 [nucl-ex]. [3] L. Adamczyk *et al.* (STAR Collaboration), Phys. Rev. Lett. **110**, 142301 (2013), arXiv:1301.2347 [nucl-ex]. [4] U. Gursoy, D. Kharzeev and K. Rajagopal, arXiv:1401.3805 [hep-ph]. [5] A. Rybicki and A. Szczurek, Phys. Rev. C **87**, 054909 (2013), arXiv:1303.7354 [nucl-th].

Speakers: Andrzej Rybicki (Institute of Nuclear Physics, Polish Academy of Sciences), Antoni Szczurek (Institute of Nuclear Physics, Polish Academy of Sciences, and University of Rzeszów)

Poster QM_2014.jpg

16:30 Charged Hadron Suppression at High pT in Au+Au Collisions at 200 GeV

The nuclear modification factor of single hadrons still provides one of the strongest constraints on energy loss mechanisms in the Quark-Gluon Plasma. Currently the best measurement at RHIC is made with neutral pions. Charged hadrons have independent sources of systematic uncertainty and thus can provide additional constraints. In PHENIX, the background from conversions and weak decays mimicking high $p_{T}$ particles has limited the measurement of charged hadron to $p_{T} < 10$ GeV/$c$. The recently installed silicon vertex tracker (VTX) will be used to reject this background allowing the measurement of charged hadrons out to $20$ GeV/$c$. The VTX is capable of performing precision tracking measurements of distance of closest approach to the primary vertex (DCA). Conversions and weak decays do not originate from the primary vertex and are vetoed with the VTX by rejecting tracks with large DCA. The status of high $p_{T}$ charged tracking and associated nuclear modification factors will be reported.

Speaker: Mr Jason Bryslawskyj (CUNY Baruch)

Slides Bryslawskyj_QM2014_poster.pdf

16:30 Charged jets in p-Pb collisions with the ALICE detector

Highly energetic jets are sensitive probes for the kinematics and the topology of high energy collisions. They are produced in an early stage of the collision from hard scattered partons that hadronize and eventually form jets as a spray of charged and neutral particles. The measurement in p-Pb provides an important reference to study the effects of cold nuclear matter on jet production and hadronization. This is possible because the formation of a hot and dense medium like in Pb-Pb is not expected. Besides the comparison to Pb-Pb collisions, p-Pb analyses can also be an important constraint for the nuclear parton density functions providing information about the nuclear environment. In terms of analysis techniques, the exact evaluation of the background from the underlying event is an important ingredient. It is much smaller than in Pb-Pb so that the methods for background estimation need to be refined. Our jet analysis of p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV is performed on data taken by the ALICE detector at the LHC in the beginning of 2013. The focus of our analysis lies on the jet spectra and their comparison to the spectra from pp collisions, including results depending on the multiplicity or centrality classes given in p-Pb collisions. For this analysis various estimates for the background and its fluctuations have been tested in p-Pb and PYTHIA MC simulations. Also, different unfolding settings have been evaluated.

Speaker: Rudiger Haake (Westfaelische Wilhelms-Universitaet Muenster (DE))

Poster 2014-May-12-conferencefile-Poster.pdf

16:30 Charged Kaon Reconstruction in Au+Au-Collisions at 1.23 AGeV with HADES

In the energy regime of 1-2 AGeV, strangeness is produced below its nucleon-nucleon production threshold, this results in a steep excitation function. Due to their quark content, positive and negative kaons have different nucleon-nucleon production thresholds. Furthermore K$^{+}$ are supposed to feel a repulsive kaon nucleon potential, while K$^-$ can be resonantly absorbed by nucleons. HADES, installed at GSI Helmholtzzentrum fuer Schwerionenforschung in Darmstadt, Germany, provides excellent capability to measure rare kaon signals. In April and May 2012, 7.3 billion Au(1.23 GeV per nucleon)+Au collisions have been recorded by HADES. In this contribution preliminary particle spectra of charged kaons will be presented. The results will be discussed with respect to the production mechanism.

Speaker: Heidi Schuldes (Goethe-University Frankfurt)

16:30 Charged particle pseudorapidity distribution in Cu+Au, Au+Au, and U+U collisions as measured with the PHENIX silicon vertex detector.

In light of the recently realized possibility of hydrodynamic flow in small systems, we will study the charged particle pseudorapidity distribution as a function of collision centrality in the transition region between very peripheral and semi-central collisions, which still has not been carefully mapped out. Pseudorapidity distributions of charged particle production are important when characterizing the collision dynamics of relativistic heavy ions. We will compare systems with different collision geometry including Cu+Au, Au+Au, and U+U at top RHIC energy. The PHENIX silicon vertex detector will be used to make these measurements in the pseudorapidity interval of |$\eta$| < 2.

Speaker: Mr Zachary Rowan (CUNY Baruch for the PHENIX collaboration)

Poster qm14_poster_zrowan.pdf

16:30 Charged particle transverse momentum spectra measured at mid-rapidity by STAR in the RHIC Beam Energy Scan

Quenching of high transverse momentum ($p_{\mathrm{T}}$) charged hadrons can be measured by the nuclear modification factor, which compares binary collision-scaled $p_{\mathrm{T}}$ spectra from central heavy-ion collisions to a reference spectrum, either proton-proton ($R_{\mathrm{AA}}$) or peripheral heavy-ion collisions ($R_{\mathrm{CP}}$), by taking their ratio. At $\sqrt{s_{\mathrm{NN}}}\ge$ 62.4 GeV the nuclear modification factor at high $p_{\mathrm{T}}$ is observed to be suppressed, i.e. less than unity, which is consistent with quenching. Measurements by STAR of charged hadron $R_{\mathrm{CP}}$($\sqrt{s_{ \mathrm{NN}}}$, $p_{\mathrm{T}}$) for $\sqrt{s_{ \mathrm{NN}}}$ = 7.7 - 200GeV show a smooth transition from strong enhancement of high $p_{\mathrm{T}}$ charged hadrons at $\sqrt{s_{ \mathrm{NN}}}$ = 7.7 GeV to strong suppression at $\sqrt{s_{ \mathrm{NN}}}$ = 200 GeV. These data will be compared with the event generators UrQMD, HIJING and AMPT. RHIC's broad range of collision systems and energies allow us to test the assumptions of the event generators; facilitating the investigation of the relative contributions from processes that lead to suppression and enhancement in heavy-ion collisions as a function of $\sqrt{s_{ \mathrm{NN}}}$.

Speaker: Stephen Horvat (STAR)

Slides HorvatQM2014_v6.pdf

16:30 Charm quark dynamics in the QGP

We study the in- and out-off equilibrium dynamics of heavy quarks in the strongly interacting partonic and hadronic medium within the Parton-Hadron-String Dynamics (PHSD) transport approach [1] which incorporates explicit partonic degrees-of-freedom in terms of strongly interacting quasi-particles (quarks and gluons) in line with an equation of state from lattice QCD as well as the dynamical hadronization and hadronic collision dynamics in the final reaction phase. The off-shell properties of quasi-particles- masses and widths - are described within the Dynamical Quasi-Particle Model (DQPM) and strongly depend on the temperature. We calculate the different cross sections for perturbative partons (massless on-shell particles in the vacuum) and for dynamical quasi-particles (off-shell particles in the QGP medium as described by the DQPM) using the leading order Born diagrams [2]. We find that the finite width of the quasi-particles in the DQPM-which encodes the multiple partonic scattering - has little influence on the cross section for qQ ->qQ as well as gQ ->gQ scattering except close to thresholds. Thus when studying the dynamics of energetic heavy quarks in a QGP medium the spectral width of the charm quarks may be discarded. Using the obtained on- and off-shell cross sections we have calculated the transport properties of the charm quarks in an equilibrated QGP such as the relaxation time [3], dynamical collisional energy loss, drag and diffusion coefficients, longitudinal and transverse momentum fluctuations, etc. Finally we incorporate the charm scattering processes in the PHSD transport approach and study the dynamics of heavy quarks in realistic heavy-ion collisions addressing observables such as the elliptic flow v_2 and R_AA. [1] W. Cassing, and E. L. Bratkovskaya, Nucl.Phys. A831 (2009) 215-242. [2] H. Berrehrah, E. Bratkovskaya, W. Cassing, P.B. Gossiaux, J. Aichelin, and M. Bleicher, arXiv:1308.5148. [3] H. Berrehrah, E. Bratkovskaya, W. Cassing, P.B. Gossiaux and J. Aichelin, arXiv:1311.0736.

Speaker: Dr Hamza Berrehrah (Frankfurt Institute for Advanced Studies (FIAS))

16:30 Charm Quark Medium Modification within a Linearized Boltzmann Approach

Heavy-flavour probes of the quark-gluon plasma (QGP) have yielded a number of surprising results. Due to their large mass and the temperature scale of the collision, it was anticipated that the charm and bottom quarks would interact weakly with the produced medium. It therefore came as a surprise when experimental results for D mesons indicated charm quarks with small $R_{AA}$ and large elliptic flow $v_n$. This suggests that heavy-flavour probes are sensitive to the collective dynamics of the QGP medium which are now well described by viscous hydrodynamics. What is, however, not so well understood is the value of the coupling of the heavy quarks to the QGP medium. In this study, we couple the evolution of open charm quarks to viscous hydrodynamics using a linearized Boltzmann equation [1] with pQCD based matrix elements for the heavy-quarks interacting with the QGP medium. We compare the elastic energy loss transport coefficients $\hat{e}$ and $\hat{q}$ in this scheme for an infinite medium at finite temperature against those extracted using a Langevin equation which describes the kinematics of the Boltzmann equation in the limit of small momentum transfer. We also examine the charm response to a thermal medium with fixed velocity profile, and present first results for charm elastic energy loss in a realistic medium described by viscous hydrodynamics coupled to a hadronic afterburner [2]. [1] J. Auvinen, K. J. Eskola and T. Renk, Phys. Rev. C **82**, 024906 (2010). [2] H. Song, S. A. Bass and U. Heinz, Phys. Rev. C **83**, 024912 (2011).

Speaker: J. Scott Moreland (Duke University)

Poster poster.pdf

16:30 Charmonia formation in quark-gluon plasma

Using the color evaporation model, the cross section for charmonium production in p+p collision is calculated in quark-gluon plasma. The threshold energy for open charms is given by the free energy potential from lattice calculations, the initial charm quark pairs by the Pythia simulations, and their time evolution by solving the Langevin equation. It is found that the threshold energy which decreases with temperature reduces the cross section while the invariant mass of charm pair which decreases by collisions enhances it. As a result, charmonia production is suppressed by 30$\sim$50 % while $J/\psi$ production is similar or enhanced compared to in vacuum.

Speaker: Dr Taesoo Song (Frankfurt Institute for Advanced Studies)

Slides Charmonia_formation_in_QGP.pdf Charmonia_formation_in_QGP.pptx

16:30 Chemical and Thermal analysis of LHC data within a blast-wave model with two freeze-outs

Within a blast-wave model which assumes two different freeze-outs, i.e. the chemical and thermal ones, both the hadron multiplicities and the transverse momentum spectra of various hadrons are analyzed in one model. In this calculation multiplicities of both the thermal hadrons and those decayed from resonances in a certain rapidity interval are calculated separately and the sum is fitted to the data. Usually the measured number of hadrons within a certain rapidity interval is converted into a number of hadrons in the whole rapidity region and the number in the whole rapidity region is regarded as a sum of the thermal ones and those decayed from resonances and fitted. This procedure is correct only when the rapidity distributions of both the thermal hadrons and the decayed ones are same. Once the chemical analysis is done, by fixing the number of thermal hadrons of a certain species as the one at the chemical freeze-out, the transverse momentum spectra of various hadrons are fitted. Hence the adjustment of magnitudes of the pT spectra of various hadrons is not necessary.

Speaker: Prof. Kang Seog Lee (Chonnam National University)

Slides qm2014-kslee.ps

16:30 Chemical Freeze-out Irregularities and Quark Gluon Bags Formation

We made a thorough analysis of the hadron resonance gas model for the Breit-Wigner and for the Gauss resonance width parameterizations [1]. The latter model allows us to treat the usual hadrons and the quark gluon bags on the same footing and to study the stability of the results obtained within different formulations of the hadron resonance gas model. Three versions of this model are fitted to reproduce 111 independent hadronic multiplicity ratios measured for 14 values of the center of mass collision energies in the interval $\sqrt{s_{NN}} =$ 2.7--200 GeV. We found that in a narrow range of collision energy $\sqrt{s_{NN}} =$ 4.3--4.9 GeV there exist the peculiar irregularities in various thermodynamic quantities calculated at chemical freeze-out. The most remarkable irregularity is an unprecedented jump of the number of effective degrees of freedom observed in this narrow energy range which is seen in all realistic versions of the hadron resonance gas model. Thus, the ratio of the freeze-out entropy density to the cube of its temperature and the ratio of the freeze-out pressure to its temperature to the fourth are, respectively, increased in 1.67 and 1.5 times, while the center of mass collision energy changes on about 14 \% (see figure below). We are arguing that these irregularities evidence for the formation of quark gluon bags. To understand such irregularities we study the apparent width of wide hadronic resonances and quark gluon bags in a thermal medium. We discuss two new effects generated for the wide resonances and quark gluon bags by a thermal medium near the threshold of decay: their thermal enhancement and their thermal sharpening. We argue that the most optimistic chance to experimentally find the quark gluon bags may be related to their sharpening and enhancement in a thermal medium. In this case the wide quark gluon bags may appear directly or in decays as narrow resonances which are absent in the tables of elementary particles and which have the width of about 50-150 MeV and the mass of about or above 2.5 GeV. 1. K. A. Bugaev, A.I. Ivanytskyi, D. R. Oliinychenko, E. G. Nikonov, V. V. Sagun and G. M. Zinovjev, arXiv:1312.4367 [hep-ph].

Speakers: Mr Dmytro Oliinychenko (Frankfurt Institute for Advanced Studies, Frankfurt, Germany), Prof. Kyrill Bugaev (Bogolyubov Institute for Theoretical Physics, Kiev, Ukraine)

Slides QM2014_POSTER_347.pdf

16:30 Chiral restoration and deconfinement in two-color QCD with two flavors of staggered quarks

In preparation of lattice studies of the two-color QCD phase diagram we study chiral restoration and deconfinement at finite temperature with two flavors of staggered quarks using an RHMC algorithm on GPUs [1]. We measure the chiral condensate and the corresponding chiral susceptibility as a function of the lattice coupling across the chiral transition. Using Ferrenberg-Swendsen reweighting we extract the maxima of the chiral susceptibility in order to determine pseudo-critical couplings on various lattices suitable for chiral extrapolations. These are then used to determine the relation between coupling and temperature. [1] Scheffler, Schmidt, Smith, von Smekal, arXiv:1311.4324

Speaker: Mr David Scheffler (TU Darmstadt)

Poster poster_scheffler.pdf

16:30 Chiral superfluidity in QCD

In this talk I will discuss new effects due to the appearance of the chiral superfluidity in two regimes of QCD. First, at low temperatures and finite density, where the cold pion condensate under rotation and in electromagnetic fields develops string-like defects with anomalous currents flowing along them. Second, at low density and high temperatures, slightly above the deconfinement transition, where the quark-gluon plasma (QGP) can be described as a two-component fluid with the fermionic zero-modes forming the "superfluid" component carrying all the chiral properties of the QGP. The anomalous phenomena under consideration include the chiral magnetic, chiral vortical, axial vortical, chiral electric, chiral separation and other effects. I will also comment on the nature of their temperature dependence in both regimes.

Speaker: Tigran Kalaydzhyan (Stony Brook University)

16:30 CMS Jet reconstruction

We present the latest development of a particle-flow-based jet reconstruction and underlying event subtraction algorithm in heavy ion collisions with CMS. This new algorithm uses a data-driven method to estimate the underlying event level from the forward calorimeter energy distribution, taking into account possible flow modulation. Unlike jet-level subtraction methods, this approach produces a fully subtracted "hard event" as input to algorithms such as anti-kT, that automatically clusters to the hard jets. We show its improved performance to the CMS iterative pile-up subtraction, and also compare to other jet reconstruction strategies currently used in heavy ion collisions.

Speaker: Yue Shi Lai (Massachusetts Inst. of Technology (US))

Poster qm2015-ylai.pdf

16:30 Coalescence production of J/Psi in heavy ion collisions

It has been found that the nuclear modification factor of a J/Psi meson shows no significant dependence on centrality when going from Relativistic Heavy Ion Collider (RHIC) energy to Large Hadron Collider (LHC) energy, and it is believed that the regeneration of the J/Psi meson plays an important role in the production of J/Psi mesons. In this work we investigate the effects of the J/Psi meson production by charm quark coalescence on the nuclear modification factor in heavy ion collisions. We find that the charm quark coalescence of J/Psi meson is mainly responsible for the J/psi production in low transverse momentum region.

Speaker: Sungtae Cho

16:30 Coherent $\psi$(2S) photo-production in ultra-peripheral Pb-Pb collisions at the LHC

Vector mesons are copiously produced in ultra-peripheral nucleus-nucleus collisions In these collisions, the nuclei are separated by an impact parameter larger than the sum of the nuclear radii. The interaction proceeds through the emission of a photon, generated by the electromagnetic field of one of the two nuclei, fluctuating into a quark-antiquark pair,that interacts with the target nucleus. The cross section for this process is sensitive to the gluon distribution in the nucleus and can therefore probe the nuclear gluon shadowing. The ALICE Collaboration has performed the first measurement of the coherent $\psi$(2S) photoproduction cross section in Pb-Pb collisions at the LHC. This charmonium excited state is tagged via the $\psi(2S) \rightarrow l^{+} l^{-}$ and $\psi(2S) \rightarrow J/\psi\pi^{+}\pi^{-}$ decays, where the $J/\psi$ decays into two leptons. The measured cross section and its ratio to the $J/\psi$ cross section are compared to predictions from theoretical models.

Speaker: Michal Broz (Czech Technical University (CZ))

Poster BrozQM2014Poster.pdf

16:30 Color Glass Condensate in Schwinger Keldysh QCD

Within the Schwinger-Keldysh representation of many-body QCD, it is shown that the leading quantum corrections to the strong classical color field is “classical” in the sense that the fluctuation field still obeys the classical Jacobi-field equation, while the quantum effects solely resides in the fluctuations of the initial field configurations. Within this context, a systematic derivation of the JIMWLK renormalization group equation is presented. A clear identification of the correct form of gauge transformation rules and the correct form of the matter-field Lagrangian in the Schwinger-Keldysh QCD is also presented.

Speaker: Sangyong Jeon (McGill University)

Poster poster_sj.pdf

16:30 Color path-integral Monte-Carlo simulations of strongly coupled of quark-gluon plasma

Based on the quasiparticle model of the quark-gluon plasma (QGP), a color quantum path-integral Monte-Carlo (PIMC) method for calculation of thermodynamic properties and -- closely related to the latter -- a Wigner dynamics method for calculation of transport properties of the QGP are formulated. The QGP partition function is presented in the form of a color path integral with a new relativistic measure instead of the Gaussian one traditionally used in the Feynman-Wiener path integrals. A procedure of sampling color variables according to the SU(3) group Haar measure is developed for integration over the color variable. It is shown that the PIMC method is able to reproduce the lattice QCD equation of state at zero baryon chemical potential at realistic model parameters (i.e. quasiparticle masses and coupling constant) and also yields valuable insight into the internal structure of the QGP. Our results indicate that the QGP reveals quantum liquid-like rather than gas-like properties up to the highest considered temperature of 525 MeV. The pair distribution functions clearly reflect the existence of gluon-gluon bound states, i.e. glueballs, at temperatures just above the phase transition, while meson-like bound states are not found. The calculated self-diffusion coefficient agrees well with some estimates of the heavy-quark diffusion constant available from recent lattice data and also with an analysis of heavy-quark quenching in experiments on ultrarelativistic heavy ion collisions, however, appreciably exceeds other estimates. The lattice and heavy-quark-quenching results on the heavy-quark diffusion are still rather diverse. The obtained results for the shear viscosity are in the range of those deduced from an analysis of the experimental elliptic flow in ultrarelativistic heavy ions collisions, i.e. in terms the viscosity-to-entropy ratio.

Speaker: Prof. Vladimir Filinov (Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, Russia)

Poster FilinovQM2014.pdf

16:30 Complex heavy quark potential at high temperature from lattice QCD

A precise definition of the $Q\bar Q$ potential at high temperature was obtained in the framework of effective field theories. The potential was calculated in hard thermal loop resummed perturbation theory and happens to be complex [1]. In ref. [2] the definition was adapted to Euclidean lattice simulations but difficulties were encountered with the infinite real time limit required to extract the potential. I will discuss how to disentangle precisely the short and long time physics from which the potential is defined [3] and present a new method to perform the analytic continuation from Euclidean to real time [4]. After these improvements, the procedure to extract the potential produces precise results [5] and its application to quenched lattice QCD data [4, 6] gives us an estimate of both the real and imaginary part of the nonperturbative complex $Q\bar{Q}$ potential across the phase transition. The final results are very encouraging since the precision obtained for the real part of the potential is below the percent level. Even if only a rough estimate of the imaginary part is obtained in ref [4], we show that it could also be settled by more precise Euclidean data. [1] M. Laine, O. Philipsen, P. Romatschke and M. Tassler, JHEP 0703 (2007) 054 [2] A. Rothkopf, T. Hatsuda and S.Sasaki, Phys. Rev. Lett. 108 (2012) 162001 [3] Y. Burnier and A. Rothkopf, Phys. Rev. D 86 (2012) 051503 [4] Y. Burnier and A. Rothkopf, Phys. Rev. Lett. 111 (2013) 182003 [5] Y. Burnier and A. Rothkopf, Phys. Rev. D 87 (2013) 114019 [6] Y. Burnier and A. Rothkopf, In preparation

Speaker: Dr Yannis Burnier (EPFL)

Poster Poster2_1.pdf

16:30 Concept and performance of the Silicon Tracking System for the CBM experiment at FAIR

The Silicon Tracking System (STS) is the central detector system of the CBM experiment. Its task is to perform track reconstruction and momentum determination for all charged particles created in beam-target collisions at SIS 100 and SIS 300 beam energies. The technical challenges to meet are a high granularity matching the high track densities, a fast self-triggering read-out coping interaction rates up to 10 MHz, and a low mass to yield high momentum resolution. We introduce the concept of the STS, being comprised of eight tracking stations employing double-sided silicon microstrip sensors on modular structures that keep the read-out electronics outside the physics aperture. The detector system acceptance covers polar angles between 2.5 and 25 degrees and will be operated in the 1 T field of a super conducting dipole magnet. The performance of the STS with respect to hit finding, track reconstruction and momentum resolution are shown based on simulation studies using a realistic geometry and detector response based on the evolving engineering and prototyping effort.

Speaker: Dr Minni Singla (GSI)

Poster CBM-STS-poster-M.Singla.pdf

16:30 Confronting current NLO charged-hadron fragmentation functions with LHC data

The recent LHC and Tevatron data for inclusive high-$p_T$ charged hadron production in p+p(${\rm \bar{p}}$) collisions show a discrepancy in comparison to the NLO perturbative QCD predictions with modern fragmentation functions (FFs). We have quantified this observation by a systematic comparison between the calculations with different FF sets and data for several collision energies [1]. We show that especially the predictions with the most recent FFs clearly overshoot the high-$p_T$, high-$\sqrt{s}$ data even when the scale variations, and uncertainties in the PDFs and FFs are accounted for. We conclude that this behavior is due to the too hard gluon-to-hadron FFs, which calls for a complete re-analysis of the FFs using the high-$\sqrt{s}$ data at $p_T > 10\,\rm{GeV}$ where the theoretical uncertainties are only modest. We discuss also to what extent these discrepancies affect the interpretation of the LHC p+Pb collision data. [1] D. d'Enterria, K.J. Eskola, I. Helenius and H. Paukkunen, *Confronting current NLO parton fragmentation functions with inclusive charged-particle spectra at hadron colliders*,  arXiv:1311.1415 [hep-ph], submitted to Nucl. Phys. B.

Speaker: Hannu Paukkunen (University of Jyväskylä)

Poster QM2014_Helenius_v3.pdf

16:30 Conserved Charge Fluctuations and Susceptibilities in Strongly Interacting Matter

The conserved charge fluctuations, as quantified by the corresponding susceptibilities, provide important information about the charge-carriers and their dynamical correlations in strongly interacting matter such as the quark-gluon plasma. Using the gauge-gravity correspondence approach, we study the patterns of conserved charge fluctuations in two types of holographic models for QCD, the D4/D8 and the D3/D7 models. We compute and compare the quark number susceptibilities in both models and find an interesting common feature of the two: at very strong coupling higher order susceptibilities are suppressed and the conserved charge fluctuations become purely Gaussian. In light of the state-of-the-art lattice QCD results we also discuss what we can learn from these susceptibilities about the underlying degrees of freedom in the $1\sim 2 T_c$ quark-gluon plasma and examine the viability of different ideas such as holography, quasi-particles, as well as bound states. From analysis of second order cross-flavor susceptibilities we conclude that the bound states exist and are important in the $1\sim 2 T_c$ region. Based on that we have further constructed model with predictions for several ratios of fourth-order susceptibilities that are in good agreement with lattice QCD results. Reference: Shuzhe Shi and Jinfeng Liao, JHEP06(2013)104[arXiv:1304.7752].

Speaker: Shuzhe SHI (Tsinghua University)

Poster Hydro_Noise_poster.pdf

16:30 Constraining dissipative corrections to particle distributions at freeze out from anisotropic flow

A decoupling dissipative fluid emits particles differently from an ideal one. The modification can be estimated with the help of a saddle-point calculation, which amounts to the limit of a low freeze-out temperature. Computing the anisotropic flow coefficients, we show that relations between different harmonics valid in the ideal case for particles with a higher velocity than the fluid no longer hold. This may be exploited to actually constrain the functional shape of the dissipative corrections, and thereby the transport coefficients of the fluid at freeze out.

Speaker: Nicolas Borghini (University of Bielefeld)

Poster Lang_Borghini_poster.pdf

16:30 Constraining global initial geometry with directed flow

Hydrodynamic simulations together with models for the fluctuating initial conditions lead to a good description of experimental data on all flow harmonics. To complement these analyses which allow to constrain initial fluctuations, one can use rapidity-odd directed flow to unravel the global initial geometry. We discuss what properties of the tilt of the initial state is necessary to reproduce data on v1(y) and v1(b). We argue that skewness (asymmetry in the transverse overlap region) of the initial state is needed to reproduce data on v1(pt). We conclude by computing tilt and skewness of various initial conditions and showing which are consistent with data on rapidity-odd directed flow.

Speaker: Frederique Grassi

Poster poster_QM14.pdf

16:30 Constraining initial stages of heavy-ion collisions from RHIC and LHC data

We propose a systematic approach for constraining models of initial conditions using a combined analysis of elliptic $v_2$ and triangular $v_3$ flow data with viscous hydrodynamic calculations. For $v_2$ and $v_3$ harmonics the hydrodynamic response to the initial state is dominated by linear response, which means $v_2$ is proportional to the ellipticity $\varepsilon_2$ and $v_3$ is proportional to the triangularity $\varepsilon_3$, i.e. $v_n = C_n\varepsilon_n$, where $C_n$ is the linear response coefficient. Experimental data on elliptic and triangular flow, combined with the calculation of $C_n$ in relativistic hydrodynamics, provide us with rms values of initial anisotropies $\varepsilon_2$ and $\varepsilon_3$. By varying free parameters in hydrodynamic calculations, we get an allowed region in the (rms $\varepsilon_2$, rms $\varepsilon_3$) plane. Thus we are able to compare Monte Carlo models of the initial state with the allowed region and exclude several of these models. We provide a simple test that can be performed on any candidate model to determine its compatibility with data. We also illustrate that the effect of changing the granularity of the initial state is similar to changing the medium properties, making these effects difficult to disentangle using only these data. [Reference: E. Retinskaya, M. Luzum and J. -Y. Ollitrault, Phys. Rev. C 89, 014902 (2014)]

Speaker: Ekaterina Retinskaya (CEA)

Poster Retinskaya_posterQM.pdf

16:30 Constraining the vector interaction strength of QCD

We show how repulsive interactions of deconfined quarks as well as confined hadrons can be constrained in a straight forward way by model comparisons of baryon number susceptibilities with lattice QCD results . We also discuss implications for earlier constraints, extracted from the curvature of the transition line of QCD and compact star observables. Our results clearly point to a strong vector repulsion in the hadronic phase and near-zero repulsion in the deconfined phase.

Speaker: Jan Steinheimer

Poster poster_qm14.pdf

16:30 Correction Methods for Finite-acceptance Effects in Two-particle Correlation Analysis

Two-particle correlations have been widely used as a tool to explore particle production mechanisms in heavy ion collisions. The mixed-event method is generally considered as a standard method to correct correlation functions for effects of finite acceptance. We demonstrate that additive correlated signals, such as jets, are distorted by the mixed-event method and propose new methods for more accurate finite-acceptance corrections and background-rejection effects. Correlation functions from the mixed-event method and the proposed new methods are compared through particle-level PYTHIA simulations containing well-defined correlation signals. Significant differences are observed at large $\Delta\eta$ in general and especially in the case of an asymmetric particle distribution like that observed in proton-lead collisions. The applicability and validity of the new methods are discussed in detail.

Speaker: Saehanseul Oh (Yale University (US))

Poster SaehanseulOh_QMposter.pdf

16:30 Cross section fluctuations in hadronic nad nuclear collisions

The nucleon-nucleon collision profile, being the basic entity of the wounded nucleon model, is usually adopted in the form of hard sphere or the Gaussian shape. It has been noticed recently [1] that the cross section fluctuations, given by the gamma distribution, lead to the profile function which smoothly ranges between the both, above mentioned, limiting forms. Nucleon-nucleon cross section fluctuations have been evaluated from the elastic differential cross section, multiplicity fluctuations and attenuation of cosmic rays. Energy dependence of cross section fluctuations has been compared with model predictions and other existing estimates. Examples of some initial state characteristics (fluctuations of target participants, cross sections dependence of mass number and energy, among others) of proton-nucleus and nucleus-nucleus collisions at wide range of center of mass energies demonstrating sensitivity on cross section fluctuations will be discussed. [1] M. Rybczynski and Z. Wlodarczyk, J. Phys. G41 (2014) 015106.

Speaker: Maciej Rybczynski (Jan Kochanowski University (PL))

Slides rybczynski_qm2014.pdf

16:30 Cumulative Particle Production in p+A Collisions and z-Scaling

Experimental data on inclusive charged particle spectra in p+A collisions are analyzed in the framework of z-scaling. The data on cross sections were taken by groups of G.Leksin at FNAL (Batavia), L.Zolin and V.Gapienko at IHEP (Protvino) with nuclear targets from beryllium up to tungsten. Spectra cover a special kinematics known as a cumulative region. Cumulative particles can be only produced in nuclear collisions. Their production is assumed to be sensitive to the state of the nuclear matter formed at the extreme conditions. Theory of z-scaling is developed for analysis of the cumulative processes and search for phase transition effects. The concept of z-scaling is based on principles of self-similarity, locality and fractality of constituent interactions at small scales. The momentum spectrum of the inclusive particle is recalculated to scaling function Ψ(z) which depends on self-similarly parameter z. A microscopic scenario of pA interactions in terms of momentum fractions x1, x2 is discussed. Results of the analysis are compared with the noncumulative data on high-pT hadron production in pA collisions obtained by J.Cronin, R.Sulyaev and D.Jaffe groups. Universality of the shape of function Ψ(z) is used to predict inclusive cross sections of particles produced in the deep-cumulative region.

Speaker: Alexey Aparin (JINR)

Poster Aparin_QM14_v12.pdf

16:30 D-meson propagation in hadronic matter and consequences on heavy-flavor observables in ultrarelativistic heavy ion collisions

Models for the heavy flavor production in ultrarelativistic heavy ion collisions suffer from a lack of elliptical flow as compared to the experimental data if they reproduce $R_{\rm AA}$, often referred to by experimentalists as a "tension between $R_{\rm AA}$ and $v_2$". One possible reason for this discrepancy may be the disregard of D-meson rescattering in hadronic matter in the latest stage of the evolution. To study this is the core of our contribution. The drag and diffusion coefficients of D-mesons propagating in a hot and dense hadronic matter are calculated. The hadronic medium consists of pions, kaons, etas, rho-mesons and nucleons. We find that the transport coefficients increase with the temperature of the medium. The dominant contributions to the drag and diffusion coefficients come from pions, but at higher temperatures the contributions from other (heavier) hadrons become important as well. In addition, we evaluate the thermal relaxation rate of D-mesons, which is in agreement with the model estimate of He, Fries and Rapp. The relaxation rate reaches approx. 0.1/fm in the vicinity of the critical temperature; this is comparable to non-perturbative T-matrix calculations of charm-quark relaxation in QGP. The size of the transport coefficients in hadronic matter shows that the hadronic contributions should be included when evaluating the nuclear suppression factor and the elliptic flow for single leptons originating from the decays of D-mesons or for D-mesons during the expansion of the matter created in heavy ion reactions at mid-rapidity. Finally, we study the consequence for the $R_{\rm AA}$ and $v_2$ of heavy mesons by using a hydrodynamical model for the expansion of QGP and the hadron gas in which the chemical freeze-out is modelled by the effective chemical potential. We present the modification of the $R_{\rm AA}$ and $v_2$ of D-mesons due to the hadronic rescattering, for both, RHIC and LHC energies.

Speaker: Dr Vitalii OZVENCHUK (subatech)

16:30 DCA and secondary vertex measurement of electron pairs using PHENIX-VTX

The bottom quark is a powerful probe to study the characteristics of QGP created in the high energy heavy ion collisions. The bottom production can be measured using the non-prompt $J/\psi$ from B decays (B -> $J/\psi$ + X). It is possible to identify the $J/\psi$ through electron pairs measuring a displaced vertex position using the silicon vertex detector (VTX). In this poster, we will report the current status of the analysis measuring the DCA and secondary vertex of electron pairs from non-prompt $J/\psi$ decays with PHENIX-VTX.

Speaker: Dr Takashi Hachiya (RIKEN)

Poster QM14_poster_TakashiHACHIYA.pdf

16:30 Deconfinement phase transition with heavy quarks

We explore the influence of heavy quarks on the deconfinement phase transition in an effective model for gluons interacting with dynamical quarks in color SU(3). With decreasing quark mass, the strength of the explicit breaking of the Z(3) symmetry grows and the first-order transition ends in a critical end point (CEP). The nature of the critical endpoint is examined by studying the longitudinal and transverse fluctuations of the Polyakov loop, quantified by the corresponding susceptibilities. The longitudinal susceptibility is enhanced in the critical region, while the transverse susceptibility shows a monotonic behavior across the transition point. We also investigate the dependence of the CEP on the number of quark flavors at zero and finite quark density. Finally we confront our model results with lattice calculations and present a formula linking the hopping parameter to the quark mass.

Speaker: Dr Lo Pok Man (GSI)

Poster qm2014_pml.pdf

16:30 Description of ${\langle p_{\mathrm{T}}\rangle}$-${N_{\mathrm{ch}}}$ correlations in pp, pA and AA collisions in Monte Carlo model based on the interaction of color dipoles

The correlation between the mean transverse momentum and the multiplicity of charged particles, recently measured by the ALICE experiment in ${{\mathrm {p\kern-0.05em p}}}$, ${{\mbox{p-Pb}}}$ and ${{\mbox{Pb-Pb}}}$ collisions at LHC, is studied in the framework of string-parton Monte-Carlo model, in which the elementary collisions are realized by interactions of color dipoles. It enables to describe pA and AA scattering without referring to the Glauber picture of independent nucleon collisions and to include the account of string fusion as a source of collectivity effects. The model reproduces multiplicity yields in wide energy range (from ISR to LHC) as well as the centrality dependence of multiplicity in ${{\mbox{Pb-Pb}}}$ collisions. The results obtained in the framework of the model for ${\langle p_{\mathrm{T}}\rangle}$-${N_{\mathrm{ch}}}$ correlations describe the main features of the experimental data. The contribution of different mechanisms to ${\langle p_{\mathrm{T}}\rangle}$-${N_{\mathrm{ch}}}$ correlation is analyzed.

Speaker: Vladimir Kovalenko (St. Petersburg State University (RU))

Poster posterQMKovalenko.pdf

16:30 Detailed study of parton energy loss via measurement of fractional momentum loss of high $p_T$ hadrons in $d$+A and A+A collisions

High $p_{T}$ hadrons as fragments of hard scattered patrons are a powerful tool to probe the opacity of the system produced in nucleus collisions, through the loss of their momenta in the medium created. In the last decade, the momentum loss was quantified in terms of suppression of the yield at given $p_T$. We recently measured the fractional momentum loss ($\delta p_{T}/p_{T}$, where $p_T$ being original momentum of a hadron, and $\delta p_T$ being the loss of its momentum in the medium) of the hadrons statistically, and found that the partons lose 1.5 times larger $\delta p_{T}/p_{T}$ in central 2.76TeV Pb+Pb collisions at the LHC than that in 200GeV Au+Au collisions at RHIC. We are extending the $\delta p_{T}/p_{T}$ measurement over different collisions species and cms energies to study a systematic trend. It is also interesting to see how the trend connects to the smaller systems like $d(p)$+A collisions which recently have revealed their possible collective nature. The measurement of emission angle dependent momentum loss of hadrons would also be interesting in the systems. We will report a detail investigation of parton energy loss in $d(p)$+A and A+A systems using high $p_T$ hadrons.

Speaker: Takao Sakaguchi (BNL)

Poster Sakaguchi_FracMomLossPoster_v3.pdf

16:30 Determination of charm quark diffusion parameter with improved Baysian analysis in lattice QCD

We study the transport property of charm quarks at finite temperature in quenched lattice QCD with improved maximum entropy method (MEM). We extend the MEM analysis to the product space of spectral functions at more than two different momenta to take advantage of more data and the strong correlation among Euclidean correlators with different momenta. We find that this method drastically reduces the error of the reconstructed images, in particular, at small energy. We apply this method to extract the diffusion coefficient of charm quarks. We also perform an error estimate of the result, which has not been carried out correctly in previous analyses. Our analysis gives finite diffusion coefficients with statistical significance and small errors. Our method and result on the basis of first principle calculations will shed light on understanding on the dynamics of heavy quarks in QGP.

Speaker: Mr Atsuro Ikeda (Osaka University)

Poster qm20142.pdf qm2014.pptx

16:30 Determination of tolerances of mirror displacement and radiator gas impurity for the CBM RICH detector

The Compressed Baryonic Matter (CBM) experiment will be a dedicated heavy-ion experiment at the future FAIR facility. In order to identify electrons, a RICH detector and several layers of TRDs will be employed. The RICH detector will be operated with CO2 as a radiator gas, a spherical glass mirror plane, and MAPMTs as photon detectors. The mirror system consists of about 70 square mirror tiles of an area of about 40x40 cm2 each. To verify the developed RICH concept a laterally scaled prototype has been constructed, in which all modules of the main components have approximately the same dimensions and properties as foreseen for the full detector. The mirror system of the prototype consists of four tiles, which enables studies of mirror-boarder effects on Cherenkov rings and their reconstruction and fit quality. The prototype has been implemented in the CBM software framework with realistic properties of the detector components. Its performance has been simulated and measured during beam times at the CERN-PS facility with electron-pion beams of momenta between 2 and 10 GeV/c. Besides many important aspects that guaranty successful operation of the detector, the determination of upper limits of gas impurity and mirror displacements have systematically been simulated and measured. The results will be presented in this contribution.

Speaker: Tariq Mahmoud (Universität Gießen)

Poster TariqMahmoud_QM2014_CBM-RICH_poster.pdf

16:30 Determining QCD matter viscosity from fluid dynamics with saturated minijet initial conditions in ultrarelativistic A+A collisions

Using next-to-leading order perturbative QCD and a conjecture of saturation to suppress the production of low energy quanta, we calculate the initial energy densities and formation times for the dissipative fluid dynamical evolution of the quark-gluon plasma produced in ultrarelativistic heavy ion collisions [1,2]. We identify the uncertainties of the model and demonstrate the predictive power of the approach by obtaining a good global agreement with the measured centrality dependence of the charged particle multiplicities, transverse momentum spectra and elliptic flow simultaneously for the Pb+Pb collisions at the LHC and Au+Au at RHIC. In particular, the shear viscosity-to-entropy ratio in the different phases of QCD matter is simultaneously constrained by all these data. In order to study higher cumulants $v_n$ and their event-by-event (EbyE) distributions, we are currently engaged in modeling the EbyE fluctuations of saturated minijet production in this framework [3]. Also these results will be reported. [1] R. Paatelainen, K. J. Eskola, H. Holopainen and K. Tuominen, **Phys. Rev. C87** (2012) 044904 [2] R. Paatelainen, K. J. Eskola, H. Niemi and K. Tuominen, **arXiv:1310.3105** [hep-ph], to appear in **Phys. Lett. B** [3] H. Niemi, K. J. Eskola, R. Paatelainen and K. Tuominen, work in progress

Speaker: Risto Paatelainen (University of Jyväskylä)

Poster FinalQM2014_paatelainen.pdf

16:30 Development of fast ramped superconducting magnets for SIS300

SIS300 is the second of the two planned new synchrotrons at FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. The high field values of up to 4.5 T for the dipoles require a so called $\cos{(\Theta)}$ design. The ramp rate of these magnets is 1 T/s, therefore special attention has been taken on the reduction of AC losses and the mechanical integrity of the magnets. For this, for example, new superconducting wires with small filament sizes of about 3 µm and a resistive CuMn matrix between the filaments has been developed. A full size model of a short curved dipole (4.5 m long) was designed, built and tested in a collaboration of GSI with groups of INFN in Genova, Milano and Salerno. Also two quadruple magnets and a steering dipole have been produced and successfully tested at IHEP, Protvino. The magnet design activities over the past years as well as an outlook into the future will be summarized.

Speaker: Carsten Omet (GSI Helmholtzzentrum für Schwerionenforschung mbH)

Slides SIS300_Poster_Quark_Matter.pdf SIS300_Poster_Quark_Matter.pptx

16:30 Development of prototype components for the Silicon Tracking System of the CBM experiment at FAIR

The building block of the CBM Silicon Tracking System is a detector module comprising double-sided silicon microstrip sensors, ultra-thin read-out cables, and novel front-end electronics. Various types of modules will be employed in the detector system, differing in sensor size and cable length. We report on the development of the module components. The silicon sensors have a CBM specific layout. The performance of recent full-size prototypes will be presented. The cables are stacks of two low-mass signal layers, based on fine-pitch aluminum lines, and spacers. They bridge the distance between the sensors and the read-out electronics. The electronics comprises self-triggering ASICs. The integration of sensors, read-out cables and electronics into detector modules has been realized. We summarize the construction and performance of recent prototypes.

Speaker: Pradeep Ghosh (GSI)

Poster CBM-STS-poster-P.Ghosh.pdf

16:30 Development of the photon detection system for the CBM RICH

The CBM-RICH detector is an essential component of the CBM experiment which will be build at the Facility for Antiproton and Ion Research, FAIR, in Darmstadt. It will serve for electron identification and pion suppression for particle momenta up to ~8 GeV/c. Pion suppression by up to 4 orders of magnitude is necessary in order to get access to rare di-electron decays of light vector mesons, such as the rho meson, one of the key observables to study the highly compressed matter produced in the heavy ion collision process. The CBM-RICH detector will use CO2 gas as radiator medium. Spatially resolved detection of Cherenkov photons will be achieved using Multianode Photomultipliers (MAPMT) or Microchannel plate detectors (MCP). Only these devices can provide sufficient detection efficiency, time resolution and rate capability necessary to operate the CBM experiment at Au-Au interaction rates up to 10 MHz. We have studied and compared in detail different sensor options, such as the 2x2 inch Hamamatsu H8500, the new H12700, the 1x1 inch R11265, or the XP85012 MCP from Photonis. Single photon XY scans combined with a self triggered readout system allow to achieve many different performance parameters, such as efficiency, cross talk, and dark noise in a single lab measurement. During two test beam campaigns with a CBM-RICH prototype detector at CERN-PS we could compare the different sensor options in beam. In this poster, we present our studies with respect to the photon detection system for the CBM-RICH detector.

Speaker: Christian Pauly (Bergische Universitaet Wuppertal (DE))

Poster QM2014_CBMRICH_Photodetektor_CP.pdf

16:30 Di-electron reconstruction in Au+Au@1.23 GeV/u

Systematic studies of di-electron and strangeness production in the few GeV per nucleon energy regime have been performed in the past years with the High Acceptance Di-Electron Spectrometer, installed at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt. In the most recent measurement, di-electron production for the heaviest collision system, Au+Au at the top SIS18 beam kinetic energy of 1.23 GeV/u have been investigated. For the first time in such a collision, where long lifetimes of the fireball are expected, the di-lepton signal has been obtained. Pure electron identification has been achieved by exploring information from the Ring Imaging Cherenkov detector together with a time-of-flight measurement and with an electromagnetic cascade signature in the Pre-Shower detector. Decision is taken upon the response of a neural network trained with high purity tracks. Topological cuts are used to suppress combinatorial background. In this contribution we will present details of signal extraction and the investigations of its purity based on detailed Monte Carlo studies. Furthermore, in order to extract signal form non-trivial pairs a combinatorial background has to be suppressed. The work is supported by VH-NG-823, BMBF (06FY9100I and 06FY7114), HIC for FAIR, EMMI, GSI, HGS-HIRe and H-QM.

Speaker: Mr Szymon Harabasz (TU Darmstadt)

16:30 Dielectron elliptic flow in Pb-Pb collisions at $\sqrt{s_{\mathrm {NN}}}$ = 2.76 TeV with the ALICE experiment

Correlated unlike sign dielectrons provide important and relatively clean information to access the properties of the hot and dense matter, the Quark-Gluon Plasma (QGP), created in relativistic heavy-ion collisions. Once they are produced, they traverse the fireball without interacting strongly with the medium. The collective behaviour of the dielectrons with respect to a global event plane provides rich information of the initial stage of the expanding fireball where flow starts developing. In the central barrel ($|\eta|<0.8$) of the ALICE experiment, electrons (and positrons) can be detected and identified by the Inner Tracking System, the Time Projection Chamber and the Time-Of-Flight. For the study of the dielectron elliptic flow at mid-rapidity, the VZERO scintillators at forward rapidity are used for event plane estimation to avoid auto-correlations. In this poster, a first attempt to measure the elliptic flow of dielectrons in Pb--Pb collisions at $\sqrt{s_{\mathrm {NN}}} = 2.76$ TeV with the ALICE experiment is presented. An effort is put into removing the background $v_2$ from uncorrelated unlike sign dielectrons with the mixed-event approach. A comparison to the elliptic flow of identified particles measured in the same system, as well as measurements from experiments at RHIC will be discussed. This work is expected to be the first step towards the measurement of the elliptic flow of thermal photons radiated from the fireball, which is regarded as a unique probe to study the formation time of the QGP.

Speaker: Hongyan Yang (University of Utrecht (NL))

16:30 Dielectron production in Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 200GeV at STAR

We report the STAR newest measurement of dielectron production in Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 200GeV. The data sets used in the analysis include large samples collected in 2010 and 2011 for Au+Au and 2012 for p+p which both yield about a factor of 3 more statistics compared to previously reported STAR results. We present the centrality and $p_{T}$ dependence of dielectron production from low-mass ($M_{ee}$<1.1 $GeV/c^{2}$) and intermediate-mass (1.1<$M_{ee}$<3 $GeV/c^{2}$) regions. The results were measured in the STAR acceptance at midrapidity with full azimuth coverage. The measurements are compared with various models to gain insight of underlying physics. Furthermore, we report the preliminary results of dielectron azimuthal correlation in the intermediate-mass region in Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 200GeV and compare the data with model calculations.

Speaker: Mr Yi Guo (USTC)

16:30 Diffractive vector meson production in ultraperipheral heavy ion collisions from the Color Glass Condensate

Deep inelastic scattering is a powerful tool to study the structure of hadrons and test our understanding of the strong interaction. The precise proton structure function measurements done at HERA have been a crucial test for the Color Glass Condensate effective field theory description of the high energy hadronic interactions. Ideally one would want to continue the analysis with nuclear targets where gluon saturation effects are expected to be even stronger. Because the role of the electron in DIS events is to only act as a source of virtual photons, one can study the same physics in ultraperipheral (large impact parameter) heavy ion collisions. In these events the dominant process is the one where one nucleus acts as a photon source, and one is left with a similar photon-nucleus scattering as in DIS. Recently diffractive vector meson production in ultraperipheral collisions has gained a lot of theoretical and experimental attention, because the cross section is especially sensitive to the saturation effects and also probes the spatial distribution of gluons. For example the ALICE collaboration has measured the diffractive J/Psi cross sections in lead-lead collisions [1]. We calculate coherent and incoherent diffractive vector meson production from the Color Glass Condensate framework and compare our results and predictions with the ALICE data. We discuss the dependence on the vector meson properties and the modelling uncertainties. We also present predictions for proton-nucleus collisions. [2] [1] ALICE collaboration, Phys. Lett. B718 (2013) 1273, Eur.Phys.J. C73 (2013) 2617 [2] T. Lappi, H. Mäntysaari, Phys.Rev. C87 (2013) 032201, Phys.Rev. C83 (2011) 065202

Speaker: Heikki Mäntysaari (University of Jyväskylä)

Poster heikki.pdf

16:30 Dihadron angular correlations in PbPb collisions with HYDJET++ model.

The hybrid model HYDJET++, including soft and hard physics, is employed for the analysis of azimuthal anisotropy harmonics and dihadron angular correlations measured in PbPb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The soft part of the model represents a thermal hadron production at the freeze-out hypersurface in accordance with hydrodynamical calculations. The possible triangular shape fluctuation of the initial overlap density of the colliding nuclei was implemented in HYDJET++ by the modulation of the final freeze-out hypersurface with the appropriate triangular coefficient, which results in triangular flow $v_3$. Along with elliptic flow $v_2$, it generates higher order flow coefficients, as well as a specific structure of dihadron angular correlations on relative azimuthal angle in a broad range of relative pseudoraidities ($\Delta\varphi \Delta\eta$). The comparison of model results with the LHC data on short- and long-range angular correlations is presented for different collisions centralities and transverse momenta intervals.

Speaker: Gyulnara Eyyubova (Czech Technical University in Prague, FNSPE, Prague, Czech Republic)

Slides PosterQM_EyyubovaGyulnara.pdf

16:30 Dilepton emission from heavy ion collision of Quark -Gluon Plasma

We extend to study the dilepton emission from heavy -ion collision of Quark-gluon Plasma incorporating the chemical potential and temperature dependent on quark mass. The dilepton emission rate is found to be enhanced in comparison to the earlier result of only temperature dependent value of quark mass and in comparison to other theoretical calculations. The study finds that the emission rate of dilepton through the chemical potential is increasing function depending on increasing value of chemical potential ranging from $\mu = 100 -450~$ MeV. This indicates that the overall result of dilepton emission through both temperature and chemical potential will provide better information about the signature of forming Quark-Gluon Plasma with this quasi-model quark mass. Keywords: Dilepton; Quark-Gluon Plasma

Speaker: Dr Somorendro Singh Shougaijam (University of Delhi, Delhi)

16:30 Dimuon Production in Au+Au √sNN = 200 GeV Collisions at STAR

Dimuon production, which is sensitive to the early stage of heavy-ion collisions, provides a unique tool to study the Quark-Gluon Plasma. At low invariant mass, the dimuon mass spectrum has the contributions from many mesons, such as $\eta$, $\omega$, $\eta\prime$. At the same time, the background from $\gamma$ conversion is largely suppressed compared to the background from dielectron measurement. With the Time Projection Chamber and the Time of Flight detector together, the STAR experiment at RHIC has good muon identification at low momentum ($<$0.3 GeV/$c$) with full azimuthal coverage at mid-rapidity. We present the preliminary results of the low-mass dimuon ($<$0.65 GeV/$c^2$) distribution at mid-rapidity $|y|<1$ and compare to hadronic cocktails at Au$+$Au $\sqrt{s_{NN}} = $ 200 GeV.

Speaker: Kefeng Xin

Poster kxin_dimuon_qm2014_v4.pdf

16:30 Direct photon collective flow in Au+Au collisions at $\sqrt{s_{NN}}$=200GeV

Direct photons are emitted from various processes from all stages from the beginning to the end of the high energy heavy ion collisions. Theoretical models tell that the angular emission patterns of the photons are different depending on their production mechanism. Previous published PHENIX results indicate that the second order Fourier coefficient ($v_{2}$) is positive for $p_{T}$<4.0GeV/c, which is qualitatively explained by hydrodynamical model calculations, but not quantitatively. The 3rd order Fourier coefficient ($v_{3}$) of photons has been proposed as a critical additional handle to understand photon emission. Photons emitted under the presence of strong magnetic field created in the collision would have a significant influence on $v_{2}$ and very little on $v_{3}$. In contrast, hydrodynamical models predict a sizable photon $v_{3}$. We report the latest results on the direct photon $v_{2}$ and $v_{3}$ coefficients in Au+Au collisions at $\sqrt{s_{NN}}$=200GeV.

Speaker: Sanshiro Mizuno for the PHENIX Collaboration (University of Tsukuba (JP))

16:30 Disentangling the soft and hard components of the pp collisions using the spheri(o)city approach

The complexity of the proton-proton interactions requires many theoretical models to describe the different features of the data. Typically, they are incorporated in MC event generators and their parameters are tuned to describe the average behaviour of specific quantities. However, this approach does not allow to understand in detail the impact of the different components in the measurable observables. This task is particularly important to really understand the physics of the hadronic interactions which so far have been taken as the baseline to learn about the medium created in ultra-relativistic heavy ion collisions. In this work a new method to extract meaningful information from the pp data is proposed, the aim is to use observables sensitive to e.g. partonic stages where collective effects are possible. The approach is based on the use of the event structure variables (sphericity and spherocity). This was developed in the framework of Pythia 8.180 since its pQCD content seems very well adapted for this goal. For minimum bias pp collisions at $\sqrt{s}=0.9$ and 7 TeV a discussion of the interconnection among event shapes, multi-parton interactions, abundances of final semi-hard quarks/gluons and color reconnection, is done. A study of the identified particle transverse momentum, $p_{\rm T}$, spectra and their ratios will be presented for isotropic (soft) and jetty-like (hard) events; and as a function of multiplicity. The results indicate that the baryon-to-meson ratio for soft events is larger than for the jetty-like ones, the latter case gives particle ratios compatible with NLO. The observations are explained in terms of the competition between gluons and quarks for the particle production at intermediate $p_{\rm T}$. The results are compared to LHC data and the similarities between the observed effects and those measured in pp and Pb-Pb collisions are discussed.

Speaker: Antonio Ortiz Velasquez (Universidad Nacional Autonoma (MX))

Slides icn_aortiz_v2.pdf

16:30 Domain growth and fluctuations during quenched transition to quark-gluon plasma

We model the initial confinement deconfinement transition in relativistic heavy-ion collisions as a rapid quench in view of expected rapid thermalization to a quark-gluon plasma state. The transition is studied using the Polyakov loop model, with the initial field configuration (in the confining phase) covering a small neighborhood of the confining vacuum l= 0, as appropriate for T < Tc. Quench is implemented by evolving this initial configuration with the effective potential at a temperature T >Tc. We study the formation of Z(3) domain structure and its evolution during the transition as l rolls down in different directions from the top of the central hill in the effective potential of l. When explicit Z(3) symmetry-breaking effects (arising from dynamical quark effects) are small, then we find well defined Z(3) domains, which coarsen in time. Remarkably, the magnitude plot of l shows vacuum bubble like configurations arising during the quench. This first-order transition like behavior occurs even though there is no metastable vacuum separated by a barrier from the true vacuum for the parameter values used. When the initial field configuration everywhere rolls down roughly along the same direction (as will happen with large explicit symmetry breaking) then we do not find such bubble like configurations. However, in this case we find huge oscillations of l with large length scales. We show that such large oscillations can lead to large fluctuations in the evolution of flow anisotropies compared to the equilibrium transition case.

Speaker: Dr Ranjita Mohapatra (Physical Research Laboratory)

Poster FinalQMPosterRanjita.pdf

16:30 Dynamical simulation of a linear sigma model near the critical point

The intention of this study is the search for signatures of the chiral phase transition and the impact of non-equilibrium effects. To investiage the impact of fluctuations, e.g. on the baryon density, near the chritical point or the chiral phase transition of QCD, we developed a 3+1D numerical, non-equilibrium simulation of an effective linear sigma model. Chiral fields are approximated as classical fields, quarks are described by quasi-particles via a Vlasov equation. For additional dynamics, kinetic quark-quark and chemical quark-sigma interactions have been implemented. The challenge is the consistent description of hard interactions between particles and classical fields. Therefore a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.

Speaker: Christian Wesp (Goethe Universität Frankfurt)

Poster Wesp_QM2014.pdf

16:30 Early thermal and chemical equilibration of quarks and gluons

Local equilibration of a QCD medium has been a long-standing issue in hadron physics since the discovery of a nearly-perfect fluid in heavy-ion collisions at RHIC and LHC. The pre-collision state is considered to be described as color glass condensate, which has a relatively large number of high-momentum gluons but almost no quarks. The success of hydrodynamic approaches, on the other hand, indicate that the medium should quickly turn into an equilibrated quark-gluon plasma in less than 1 fm/$c$. Equilibration of a heavy-ion system requires (i) isotropization, (ii) thermalization and (iii) chemical equilibration of partons. In this work we focus on the latter two and aim to provide an efficient description for producing low-momentum quarks and gluons by modeling collinear parton splitting and recombination processes. Parton-medium interaction, which is required for creating off-shell partons, is embedded in the model by drag and diffusion effects in relativistic Fokker-Planck equation. We perform numerical simulation in a transverse direction for qualitative analyses to find that the gluon distribution approaches the thermal one in a very short time, and quark thermal/chemical equilibration is slower than the gluon thermalization though it is reasonably fast. The recombination is suggested to be essential in chemical equilibration as quark production from over-populated low-momentum gluons would be suppressed by Pauli exclusion principle. The results imply that the collinear processes play an important role in early thermal and chemical equilibration of the QCD matter produced in high-energy heavy-ion collisions.

Speaker: Dr Akihiko Monnai (RIKEN BNL Research Center)

Poster qm14_monnai.pdf

16:30 Effect of the equation of state on particle spectra, elliptic flow and HBT radii

We present results of a systematic study of the role of the equation of state in the hydrodynamic model. By using the same initial conditions and freeze-out scenario, the effects of different equations of state are compared by calculating their respective hydrodynamical evolution, particle spectra, elliptic flow and HBT radii. Three different types of equation of state are studied, each focusing on different features, such as nature of the phase transition, strangeness and baryon densities. Different equations of state imply different hydrodynamic responses, the impact thereof on final state anisotropies are investigated. The results of our calculations are compared to the data from RHIC at 130 GeV and 200 GeV. It is found that the three equations of state used in the calculations describe the data reasonably well; differences can be observed, but they are quite small. The insensitivity to the equation of state seems to weaken the need for a locally thermalized description of the system, at least for the observables analyzed in this work. A precise determination of transport coefficients by fitting collective flow parameters in the framework of hydrodynamics still requires caution.

Speaker: Danuce Dudek (Universidade Estadual Paulista)

Poster DDudek.pdf

16:30 Effective Energy Dissipation and Particle Production in Heavy-Ion Collisions

In this report, we consider an energy dissipation model for multiparticle production in heavy-ion collisions. The model considers the energy of a collision to be transformed into the produced particles as effective energy of participants, which drives the particle-production process. Within this model, we describe the dependencies of the two key observables, namely the midrapidity charged-particle density and the midrapidity transverse energy, on the center-of-mass energy and on the number of participating nucleons. These dependencies are of great importance in understanding the dynamics of multiparticle production in heavy-ion collisions. The model combines the constituent quark picture of participants (quarks or nucleons) together with the Landau relativistic hydrodynamics [1] and is found to successfully relate the particle production in hadronic and in central nuclear interactions [2]. A good agreement with the available measurements up to the LHC energies is demonstrated clarifying the underlying dynamics of the particle production process in heavy-ion collisions. A detailed study of the bulk observables in the framework of the constituent quark energy dissipation model considered is presented. Predictions are made on the charged particle multiplicity and transverse energy density for the collision energies where experimental data are not available. References: 1. L.D. Landau, Izv. Akad. Nauk: Ser. Fiz. 17, 51 (1953), S.Z. Belenkij, L.D. Landau, Nuovo Cim., Suppl. 3, 15 (1956). 2. E.K.G. Sarkisyan, A.S. Sakharov, Eur. Phys. J. C 70, 533 (2010), AIP CP838, 35 (2005), hep-ph/0410324.

Speaker: Raghunath Sahoo (Indian Institute of Technology Indore (IN))

Poster poster_QM2014Final.pdf

16:30 Effective SU(2) Polyakov Loop Models for the Deconfinement Transition

We compare different SU(2) Polyakov loop actions with data from full two-color QCD simulations around and above the critical temperature [1,2]. The effective actions are motivated by combined strong coupling and hopping expansions. We extract the effective couplings of our models by matching Polyakov loop distributions and correlators from the efective models with those from full two-color QCD simulations. [1] Smith, Dumitru, Pisarski, von Smekal, Phys. Rev. D88 (2013) 054020 [2] Scheffler, Schmidt, Smith, von Smekal, arXiv:1311.4324

Speaker: Mr Philipp Scior (TU Darmstadt)

Poster poster_scior.pdf

16:30 Effects of shower patrons on soft and semihard hadrons produced in Pb-Pb collisions at LHC

The transverse momentum distributions of identified hadrons produced in Pb-Pb collisions at the Large Hadron Collider (LHC) are studied for $p_T$ up to 20 GeV/c. We use quark recombination to treat hadronization, applied uniformly at all $p_T$ based on a common thermal parton distribution of light and strange quarks and on shower patrons emitted in hard and semihard jets. Furthermore, we improve the treatment of momentum degradation. Since we aim to confront the $p_T$ spectra at mid-rapidity of all observed hadrons, $\pi$, K, p, $\Lambda$, $\Xi$, $\phi$ and $\Omega$, the system is highly contained. There are thousands of soft hadrons and hard jets produced in Pb-Pb collisions at 2.76 TeV. Minijets can fragment into soft patrons with multiplicities so high that their effects on the patrons created in the soft interaction of the bulk can't be ignored. So the primary feature of our work is to quantify the effect of hard and semihard jets on the soft sector. What we find is that the soft patrons generated by the hard patrons are so overwhelming at LHC, compared to the situation at RHIC. It becomes clear that the hadronization problem at LHC is drastically different from that at RHIC.

Speaker: Lilin Zhu (Sichuan University)

Poster QM14poster.pdf

16:30 Effects of the global charge conservation on the time evolution of fluctuations of conserved charges in relativistic heavy ion collisions

We investigate the effects of the global charge conservation on the rapidity window dependences of fluctuations of conserved charges observed in heavy ion collisions. We describe the time evolution of the higher order fluctuations in the hadronic medium by solving the diffusion master equation with boundaries. Our result suggests that the effect of the global charge conservation for the diffusion in the hadronic phase is negligible in the experimental results even with the largest rapidity window acceptance at ALICE unlike previously suggested. We argue that the rapidity window dependence of the charge fluctuation observed by ALICE at LHC is caused by not the global charge conservation but the time evolution of the fluctuation. The dependences of the fluctuations of conserved charges on the rapidity window contain various information on the matter generated in heavy ion collisions.

Speaker: Ms Miki Sakaida (Osaka University)

Poster sakaida(I-35).pdf

16:30 Effects of Time Evolution and Fluctuating Initial Conditions on Heavy Flavor electron R$_{AA}$ in Event-by-Event Relativistic Hydrodynamics

Effects on the heavy quarks dynamics due to the medium formed in heavy ion collisions are investigated, on an event-by-event basis, using a newly developed 2D+1 Lagrangian ideal hydrodynamic code which is based on the Smoothed Particle Hydrodynamics (SPH) algorithm. An energy loss model is used on top of the evolving space-time energy density distributions for two different schemes: fluctuating and smooth initial conditions (IC) events. The calculations are also performed for static space-time energy density distributions for these schemes. We find that the nuclear modification factor $R_\text{AA}$ is affected by hydrodynamic evolution in comparison with the static IC as expected due to the medium quenching. Furthermore, we showed how the spectrum is affected when fluctuations on the medium were considered in comparison with the smooth profile.

Speaker: Caio Alves Garcia Prado (Universidade de Sao Paulo (BR))

Poster qm2014.pdf

16:30 Eigenmode analysis of anisotropic flow

We present a new method for analyzing anisotropic flow, $v_n$, from the eigenmodes and eigenvalues of the two-particle correlation matrix $\langle\cos n\Delta\phi\rangle$, where $\Delta\phi$ is the azimuthal separation between two particles (in general from different pseudorapidity bins), and angular brackets denote an average over pairs of particles. Methods currently used to analyze anisotropic flow (event plane method, cumulant method) were devised before the importance of flow fluctuations was recognized. Our new method uses more detailed information on how the azimuthal correlation depends on the pseudorapidity (and/or transverse momentum) of both particles. This information can be used to extract flow fluctuations directly from experiment. When correlations are due to flow, all the eigenvalues are positive. The eigenmode analysis allows to write the correlation matrix as a sum, where each term in the sum corresponds to a different component of flow fluctuations. The largest eigenvalue corresponds to the usual rms $v_n$, which depends little on the pseudorapidity $\eta$, while the next-to-largest eigenvalues yield modes which typically oscillate as a function of $\eta$, and which correspond to flow fluctuations. We study the effect of nonflow correlations, and statistical errors. We test the applicability of this new method with Monte-Carlo simulations using the transport model AMPT.

Speaker: Subrata Pal (Tata Institute of Fundamental Research, Mumbai, India)

Poster poster.pdf

16:30 Elliptic and Triangular Flow of inclusive charged hadrons in Au+Au and Cu+Cu at $\sqrt{s_{NN}} =$ 200 GeV collisions at RHIC-PHENIX

Considerable attention has been given to the ​investigation​ of anisotropic flow in heavy-ion collisions at both the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). The focus of current studies in this field is centered on the influence of the initial-state geometry [and its fluctuations] and its role in the extraction of the specific shear viscosity (i.e. the ratio of shear viscosity to entropy density $\eta/s$) of the quark gluon plasma (QGP). The PHENIX measurements for elliptic ($v_2$) and triangular ($v_3$) flow in the Cu+Cu and Au+Au systems, allow detailed investigations of the respective influence of system size and initial-state fluctuations on the expansion dynamics and the associated transport coefficients. Detailed differential results for inclusive charged hadron $v_2$ and $v_3$ for both systems as well as the scaling properties of these measurements, and their implications, will be presented and discussed.

Speaker: Damian Reynolds (State University of New York, Stony Brook)

16:30 Elucidating the event-by-event flow fluctuations in heavy ion collisions via the event-shape selection and twisting techniques

Recent discovery of significant higher-order flow harmonics and theoretical study of the non-linear hydrodynamics have led to the realization of a large set of new event-by-event (EbyE) flow observables that can be measured in heavy-ion collisions. These observables can be expressed generally as a joint probability distribution of flow coefficients $v_n$ and their phases $\Phi_n$, $p(v_n, v_m, ..., \Phi_n,\Phi_m....)$. Initial measurements of a small subset of these flow observables, namely $p(v_n)$ and event-plane correlations $p(\Phi_n,\Phi_m....)$ at LHC, have already provided new insights on the geometry fluctuations in the initial state and the non-linear hydrodynamics in the final state. In a recent work, we propose an experimental method to further probe other flow observables based on the recently proposed event-shape selection technique a new event-shape twisting technique. In the first method (arXiv:1311.7091), events in fixed centrality are further divided in bins of $v_n$ values in the forward pseudorapidity ($\eta_F$). This allows us to measure how the $v_m$ and event-plane correlation respond to the change in $v_n$, which provide access to two classes of observables not studied before: $p(v_n, v_m)$ and $p(v_n, \Phi_n,\Phi_m....)$. Furthermore our method also allows a quantitative study of the correlation of $v_n$ in different rapidity: $p(v_n(\eta_F),v_n(\eta))$. The robustness of this method is demonstrated using the AMPT model, which is known to describe reasonably the centrality dependence of $v_n$ and event-plane correlations. Strong positive correlations are observed among all even harmonics v2, v4, and v6, between v2 and v5 and between v3 and v5, consistent with the effects of non-linear hydrodynamic response, while a significant anti-correlation is observed between v2 and v3. The $v_n(\eta)$ for events selected on $v_n(\eta_F)$ shows a significant forward/backward asymmetry, which indicates the de-correlation of event planes over pseudorapidity. In the second method (paper to be submitted), a twist angle between the event planes in the forward and backward rapidity is enforced by cutting on $\Delta\Phi = \Phi_n(\eta_F)-\Phi_n(\eta_B)$. This twisting procedure leads to a non-zero $\eta$-dependence $<\sin(n(\phi-\Psi_n))>$ component in between, which can be used to calculate the event plane angle as a function of $\eta$. This allows us to distinguish between two competing mechanisms for the rapidity de-correlation: a systematic rotation versus a random fluctuation of event plane angles along the $\eta$ direction. Indeed, a significant fraction of the observed rapidity de-correlation in the AMPT model is found to arise from a systematic rotation of event plane angles along the $\eta$ direction. Our studies show that the event-shape selection and event-shape twisting techniques promise to provide unprecedented details on the EbyE flow fluctuations. The prospects of applying these techniques to Au+Au/Pb+Pb collisions at RHIC and LHC are discussed.

Speaker: Mr Peng Huo (Stony Brook University)

Poster QM2014_final.pdf

16:30 Elucidating the internal structure of jets at the LHC using soft-collinear effective theory

The jet quenching phenomena, observed in heavy ion collisions at the LHC, present strong evidence for the strong modification of parton shower in the quark-gluon plasma. To understanding the longitudinal and transverse structure of medium-induced branching, observables that go beyond the suppression of inclusive and tagged jets are necessary. Here we present theoretical calculations of jet shapes in proton-proton and lead-lead collisions at the LHC using soft-collinear effective theory with Glauber gluon interactions in the medium. We find that large phase space logarithms need to be resummed for precise theoretical predictions. The resummation is performed using renormalization group evolution between different jet scales. We also study the medium modification of the renormalization group evolution and generalize the method to calculate jet shapes in heavy ion collisions. We present a comparison between our calculations with the recent jet shape measurement at the LHC. We also discuss the path to resummation of longitudinal intra-jet observables, such as jet fragmentation functions.

Speaker: Dr Yang-Ting Chien (LANL)

Slides QMposter.pdf

16:30 Energy loss in unstable quark-gluon-plasma

The quark-gluon plasma at the early stage of relativistic heavy-ion collisions is unstable due chromomagnetic plasma modes. The energy loss per unit path length of a fast parton scattering elastically in such a plasma is studied as an initial value problem. Although the approach is designed to study the unstable plasma, the well known results of equilibrium plasma are also reproduced. The energy loss in unstable QGP is shown to have strong time and directional dependence. Since the magnitude of the energy loss per unit length in an unstable QGP can be much bigger than in an equilibrium plasma, the problem is important for jet quenching in relativistic heavy-ion collisions.

Speaker: Katarzyna Deja (National Centre for Nuclear Research)

16:30 Energy Loss of Open Charm Produced In Relativistic Heavy Ion Collision

Charm quarks are produced mostly in the pre-equilibrium phase in heavy ion collision. They serve as an excellent probe for quark gluon plasma which consists mainly of light quarks and mass-less gluons. Charm loses energy and momentum in this medium and comes out ultimately as D meson or later undergoes semi-leptonic decay which is experimentally observed. Here we present the evolution and energy loss of charm quark in quark gluon plasma using the calculations of Parton cascade Model based on Microscopic Boltzmann Transport Equation.

Speaker: Mohammed Younus (Variable Energy Cyclotron Centre)

Slides Mohammed_QM2014_poster.pdf

16:30 Enhancement of Flow Harmonics due to Bulk Viscosity in Event by Event Hydrodynamics

Shear and bulk viscosity effects on the collective flow harmonics in heavy ion collisions are investigated, on an event by event basis, using a newly developed 2+1 Lagrangian hydrodynamic code named v-USPhydro which implements the Smoothed Particle Hydrodynamics (SPH) algorithm for viscous hydrodynamics. A new formula for the bulk viscous corrections present in the distribution function at freeze-out is derived starting from the Boltzmann equation for multi-hadron species. Bulk viscosity is shown to enhance the collective flow Fourier coefficients from $v_2(p_T)$ to $v_5(p_T)$ when $% p_{T}\sim 1-2.5$ GeV even when the bulk viscosity to entropy density ratio, $% \zeta/s$, is significantly smaller than $1/(4\pi)$ whereas shear viscosity enhances $v_2(p_T)$ to $v_5(p_T)$.

Speaker: Dr Jacquelyn Noronha-Hostler (University of Sao Paulo)

Poster noronhahostlerposter.pdf

16:30 Estimates of heavy-ion collision symmetry planes with the ALICE detector.

Measuring collective phenomena in heavy-ion collisions, such as anisotropic flow and its fluctuations, requires an estimate of the collision symmetry plane for different flow harmonics. Each plane's orientation is estimated from the azimuthal distribution of produced particles or from spectators' deflection. Azimuthal non-uniformity in the detector response distorts azimuthal distributions and introduces a bias in the flow measurements. We discuss a correction procedure for the collision symmetry plane estimates and its practical application for a number of ALICE subsystems situated at mid- and forward rapidity.

Speaker: Jacobus Onderwaater (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

Poster QM2014_SymmetryPlane_Onderwaater.pdf

16:30 Estimation of electric conductivity of the quark gluon plasma via asymmetric heavy-ion collisions

The quark gluon plasma (QGP), which consists of deconfined quarks and gluons, is expected to have filled the early Universe, and is also produced experimentally through the relativistic heavy-ion collisions at Relativistic Heavy Ion Collider (RHIC) in BNL and Large Hadron Collider (LHC) in CERN. There has been much effort to extract detailed properties of the QGP by constraining transport coefficients such as shear viscosity, bulk viscosity, and charge diffusion constants. We here propose a new way of estimating the electric conductivity of the QGP via asymmetric nucleus-nucleus collisions at ultrarelativistic energies [1]. Theoretically, lattice QCD simulations and perturbative QCD calculations have been utilized to estimate electric conductivity of the QGP. So far, the estimated values of have differed significantly from each other and experimental information is very much awaited. Very recently, asymmetric collisions between copper and gold nuclei have been performed at RHIC. We point out that Cu+Au collisions can be useful for extracting the electric conductivity of the QGP. We show that, in off-central Cu+Au collisions, a substantial magnitude of electric field directed from a colliding Au nucleus to Cu nucleus is generated in the overlapping region, by performing event-by-event calculations of produced electromagnetic fields. This happens only when colliding two nuclei carry the different number of electric charge. The electric field would induce a current in the matter created after the collision, resulting in a dipole deformation of the charge distribution in the medium. We show that the charge-dependent directed flow parameters $v_1^{\pm}$ of the observed hadrons are sensitive to the electric conductivity of the QGP. References: [1] Yuji Hirono, Masaru Hongo, Tetsufumi Hirano, arXiv:1211.1114.

Speaker: Yuji Hirono (The University of Tokyo)

Poster poster-hirono-A0.pdf

16:30 Event plane dependence of charged jet yields in $\sqrt{\rm s_{NN}}$ = 2.76 TeV Pb-Pb collisions with ALICE

The heavy-ion program at ALICE is aimed at studying strongly interacting matter in ultra-relativistic nuclear collisions where the formation of a quark-gluon plasma (QGP) is expected. Jets can be used to probe the QGP. Earlier studies at the LHC have shown that jet production is suppressed in heavy-ion collisions. This suppression is attributed to elastic and/or radiative interactions between the parton and the QCD medium, which transport jet momentum outside the jet cone. The dependence of the energy loss on the in-medium path length provides insight into the energy loss mechanisms. This path-length dependence can be studied by measuring the jet yield with respect to the event plane. This contribution will show results of measurements of charged jet yields in central $\sqrt{s_{\rm NN}} = 2.76 $ TeV Pb-Pb collisions with respect to the second order event plane. Jet finding is performed with the anti-k$_{\rm{T}}$ algorithm with a resolution parameter $R$ = 0.2, using charged tracks from the ALICE central tracking system. The contribution of hydrodynamic flow to the underlying event is taken into account on an event-by-event basis.

Speaker: Redmer Alexander Bertens (University of Utrecht (NL))

Poster QM2014_poster_rbertens_FIGURES_APPROVED_FINAL.pdf

16:30 Exact analytical solutions of second-order conformal viscous hydrodynamics

In this talk I will describe the recent progress towards deriving analytical solutions of 2nd order viscous conformal hydrodynamics. I will first explain the recently obtained analytical (and semi-analytical) transversally expanding solutions of 2nd order viscous conformal hydrodynamics involving the so-called boost invariant Gubser flow, which has been recently used as a powerful test regarding the precision of the existent numerical hydrodynamic codes. In the second part of the talk, I will present some new exact solutions of relativistic second-order hydrodynamic equations in theories with conformal symmetry. We construct, for the first time, fully analytical axisymmetric exact solutions of 2nd order conformal hydrodynamics including the case with nonzero vorticity. These new solutions provide a useful quantitative measure of the second-order effects in 3+1 relativistic viscous hydrodynamics.

Speaker: Jorge Noronha (University of Sao Paulo)

Slides poster_Jorge_hydro_QM2014.pdf

16:30 Exact solutions of kinetic equation in the relaxation time approximation

Experimental and theoretical studies of relativistic heavy-ion collisions showed that the behavior of matter produced in such collisions is very well described within hydrodynamic models. These results brought a lot of attention to the studies of kinetic coefficients whose values determine the magnitude of important observables such as the elliptic flow. Interestingly, different theoretical methods lead to different values of the kinetic coefficients. Our idea is to perform comparisons of exact solutions of simple kinetic equations with various hydrodynamic approaches, which allows us to select correct forms of these coefficients. For this purpose we exactly solve the relaxation-time approximation Boltzmann equation for a system undergoing boost-invariant longitudinal expansion. We compare the resulting exact numerical solutions with approximate solutions available which allows us to find correct expressions for shear and bulk viscosity coefficients. Presented work is mainly based on: W.Florkowski, R.Ryblewski, M.Strickland, Nucl.Phys. A916 (2013) 249-259 W.Florkowski, R.Ryblewski, M.Strickland, Phys.Rev. C88 (2013) 024903 W.Florkowski, E.Maksymiuk, R.Ryblewski, M.Strickland, forthcoming

Speaker: Radoslaw Ryblewski (Institute of Nuclear Physics PAS)

Poster poster_ryblewski.pdf

16:30 Exclusive J/$\psi$ photoproduction in ultra-peripheral p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

The ALICE Collaboration has measured exclusive J/$\psi$ photoproduction off protons in ultra-peripheral proton-lead collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV for the first time. Exclusive photoproduction of charmonium is a powerful tool to search for saturation effects. Although gluon saturation is the most straightforward mechanism to slow down the growth of the probability density function (PDF) for gluons at small-x, no compelling evidence for this effect has been found so far. Parton saturation would have important applications in small-x physics and in the early stages of ultra-relativistic heavy-ion collisions produced at RHIC and LHC. The results are compared to STARLIGHT and to QCD based models. We extend HERA measurements up to about the TeV energy domain without experimental ambiguity on the photon source. Our results provide direct tests of the power law dependence of the J/$\psi$ photoproduction cross section over a wide range of $\gamma {\rm p}$ energies.

Speaker: Daniel Tapia Takaki (Universite de Paris-Sud 11 (FR))

16:30 Experimental signals of the QCD first-order phase transition from a stochastic fluid dynamical model

A potential discovery of the first-order phase transition, which is conjectured in the QCD phase diagram at high net-baryon densities, would undoubtedly demand the existence of a critical point. We present results from a fluid dynamical model of the QCD phase transition in heavy ion collisions. Non-equilibrium effects in the evolution of the fluctuations of the order parameters are included via a stochastic propagation according to a Langevin equation. We observe the formation of a supercooled phase at the first-order phase transition and its subsequent fragmentation into domains in the order parameters and droplets in the baryon density. Potential experimental signals, such as an enhancement of higher harmonic flow coefficients, are discussed. Here, the correct treatment of the hadronic phase turns out to be crucial for the development and survival of experimental consequences of the first-order phase transition. Due to critical slowing down, which limits the growth of critical fluctuations in the vicinity of the critical point, we expect that the discovery of the first-order phase transition might experimentally be more feasible.

Speaker: Dr Christoph Herold

16:30 Fast Interaction Trigger for ALICE

As a result of the LHC upgrade after the Long Shutdown 2, the expected luminosity and collision rate during the so called Run 3 will considerably exceed the design parameters for several of the key ALICE detectors systems including the forward trigger detectors. Furthermore, the introduction of a new Muon Forward Tracker significantly reduces the space envelope available for the upgraded Fast Interaction Trigger (FIT) detector on the C-side. At the same time, FIT is expected to match and even exceed the functionality and performance currently secured by three ALICE sub-detectors: the time zero detector (T0), the VZERO system, and the Forward Multiplicity Detector (FMD). The harsh conditions of Run 3 would accelerate the aeging and radiation damage (detectable already during Run 1) of the FIT detector if we were to use standard PMTs. The solution came thanks to the latest developments in MCP-PMT technology providing compact photo sensors with excellent characteristics and stability. The key design features of FIT will be presented together with the latest simulation results and benchmark tests of the prototype.

Speaker: Wladyslaw Henryk Trzaska (University of Jyvaskyla (FI))

16:30 Feasibility study for the measurement of the elliptic azimuthal anisotropy of electrons from semileptonic decays of beauty hadrons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV with ALICE

In heavy-ion collisions at ultrarelativistic energies a sufficiently high temperature can be reached to form the Quark-Gluon Plasma (QGP), a deconfined state of strongly-interacting matter. Heavy quarks, i.e. charm and beauty, serve as a sensitive probe of the QGP properties since they are predominantly produced in initial hard scattering processes and interact with the hot and dense medium. The elliptic azimuthal anisotropy ($v_2$) of electrons from heavy-flavour hadron decays in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV, measured by the ALICE collaboration, has been used to probe the properties of the QGP. The measurement of $v_2$ of heavy-flavour decay electrons at low transverse momentum tests whether heavy quarks take part in the collective expansion of the deconfined medium. In addition, the measurement of $v_2$ of heavy-flavour decay electrons at high transverse momentum carries information on the path-length dependence of the heavy-quark energy loss within the QGP. We present a way to subtract the contribution of the charm decay electron $v_2$ from the heavy-flavour decay electron $v_2$. The resulting $v_2$ of electrons from beauty-hadron decays is derived from the elliptic azimuthal anisotropy of heavy-flavour decay electrons and prompt D mesons measured in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. In the near future, the significant increase of the luminosity at the LHC, as well as the ALICE detector upgrades, will increase the potential of this analysis.

Speaker: Denise Aparecida Moreira De Godoy (Laboratoire de Physique Subatomique et des Technologies Associe)

Slides poster_QM2014_DeniseGodoy.pdf

16:30 Femtoscopic analysis of charged kaon correlations at small relative momentum in $p+p$ collisions in STAR

Two-particle correlations at low relative momentum provide information on the space-time geometry of emitting sources on the femtoscopic scale. Dynamical properties of the system are reflected in the total pair momentum dependence of the correlations. We present a preliminary measurement of the multiplicity and transverse momentum dependence of charged kaon correlations at small relative momentum measured in $p+p$ collisions by the STAR detector at RHIC. Using kaons allows for the study of the emitting source radii to be extended to higher values of transverse mass. Results are presented for $\sqrt{s}=200$ and $\sqrt{s}=510$ GeV and compared to similar measurements recently reported at the LHC.

Speaker: Grigory Nigmatkulov (N)

Poster Femtoscopic analysis of charged kaon correlations at small relative momentum in p+p collisions in STAR

16:30 Femtoscopic correlations of two identical particles with nonzero spin in the model of one-particle multipole sources

The process of emission of two identical particles with nonzero spin $S$ and different helicities is theoretically investigated within the model of one-particle multipole sources. Taking into account the unitarity of the finite rotation matrix and symmetry relations for $d$--functions, the general expression for probability of emission of two identical particles by two multipole sources with angular momentum $J$, averaged over the projections of angular momentum and over the space-time dimensions of the generation region, has been obtained. For the case of unpolarized particles, the additional averaging over helicities is performed and the general formula for two-particle correlation function at sufficiently large 4-momentum difference $q$ is derived . The special cases of emission of two unpolarized photons by dipole and quadrupole sources, and emission of two "left" neutrinos ( "right" antineutrinos ) by sources with arbitrary $J$ have been also considered, and the respective explicit expressions for the correlation function are obtained .

Speaker: Dr Valery Lyuboshitz (Joint Institute for Nuclear Research ( Dubna ))

Slides Quark_Matter_2014--Valery_Lyuboshitz_3.pdf

16:30 Femtoscopy with lambda baryons in Pb-Pb collisions with ALICE at the LHC

For two-particle systems with a well known interaction, ranging from pion-pion to proton-lambda, femtoscopy is used to measure the space-time characteristics of the fireball created in heavy-ion collisions at kinetic freeze-out. For less known systems, femtoscopy can be used to extract nuclear scattering information for the particles being studied. In particular, the scattering length and effective range of interaction can be extracted from fits of femtoscopic correlation functions. This technique has applications in the study of hyperon-hyperon interactions, where precise scattering measurements are still needed. However, there are non-trivial complications due to the possible residual correlations introduced by feed-down from other hyperons when studying lambda particles. We present measurements of baryon-baryon, antibaryon-antibaryon, and baryon-antibaryon correlation functions involving lambda particles in Pb-Pb $\sqrt{s_{\rm NN}} = 2.76$ TeV collisions with ALICE. The results are compared to femtoscopic measurements from other analyses, as well as to model predictions. We also present our methodology for quantifying the correlations from feed-down.

Speaker: Jai Salzwedel (Ohio State University (US))

16:30 Fermion pair production in space-time dependent strong fields

In the early stage of relativistic heavy ion collisions a strong coherent gluonic field could form. This phenomenon is usually described by the string model and it became the basis of successful Monte Carlo event generators. The usual string picture can be connected to an assumption of a static homogeneous gluonic field. On the other hand during the collision one expects large inhomogeneities of the gluonic field in space-time. With the help of the relativistic Wigner function formalism one can describe the phase-space evolution of pair production in such fields. Our model of fermion-pair production indicates that not only the time variation plays an important role and has strong influence on the transverse momentum spectra of the newly produced particles, but the space inhomogeneities could completely change the interpretation of the string picture. As a result we demonstrate that most of the new particles are not produced in the bulk, scaling with the volume, instead one finds a scaling with $\propto V ^{\frac{2}{3}}$, in accordance with the early prediction of Heisenberg.

Speaker: Daniel Berenyi (Wigner RCP of the Hungarian Academy of Sciences, Hungary)

Poster BerenyiD_A0_poster_QM14_v0.pdf

16:30 Final state effects on charge asymmetry of pion elliptic flow in high-energy heavy-ion collisions

Within a multi-phase transport (AMPT) model with string melting mechanism and an imported electric charge quadrupole distribution in the initial partonic coordinate space, the elliptic flow asymmetry between positive and negative pions is investigated. The slope parameter $r$ of the linear dependence of $\Delta v_{2}=v_{2}(\pi^{-})-v_{2}(\pi^{+})$ on $A_{ch}=(N^{+}-N^{-})/(N^{+}+N^{-})$ is yielded by the conversion from an initial electric charge quadrupole distribution to a charge-dependent elliptic flow via a strong parton cascade process. The slope parameter $r$ is increased by the hadronization of coalescence, and then decreased by final resonance decays. Because the slope parameter $r$ is very sensitive to both initial electric charge quadrupole percentage and centrality, a helpful constraint of the effect from chiral magnetic wave is extracted out in Au+Au collisions at the top RHIC energy. Reference: Guo-Liang Ma, arXiv:1401.6502.

Speaker: Guo-Liang Ma (Shanghai INstitute of Applied Physics (SINAP), CAS)

Slides QM2014_CMW_MaGuoliang.pdf

16:30 First principle calculation of dilepton production rate in strongly interacting QGP

We analyze the production rate of dileptons from the deconfined medium using a quark propagator obtained from a first principle lattice QCD numerical simulation. We calculate the dilepton production rate non-perturbatively at two temperatures in the deconfined phase with the quark propagator measured on the lattice. The photon-quark vertex is determined gauge-invariantly, so as to satisfy the Ward-Takahashi identity. The obtained dilepton production rate shows an enhancement of order 10 or so compared with the rate from free quark systems at low invariant mass region and van Hove singularity. This rate could explain the discrepancy in the dilepton production yields in the low mass region between the PHENIX result and theoretical predictions.

Speaker: Mr Taekwang Kim (Osaka University)

Poster QM2014_poster_20140520p.pdf

16:30 Flow or Radiation in Heavy-ion Collisions?

In high energy heavy ion collisions, both thermal and hydrodynamical models have been applied quite successfully to describe single particle observables. Here we investigate a rather different approach: we analyze the classical electromagnetic radiation of an accelerating point charge moving on a straight line trajectory. Depending on the duration of accelerations, rapidity distributions of photons emerge, resembling the ones obtained in the framework of hydrodynamical models by Landau or Bjorken. Experimentally observable differences between our approach and spectra obtained from hydrodynamical models are also discussed.

Speaker: Zsolt Schram (U)

Poster zschramQM2014.pdf

16:30 Flow vorticity in Peripheral high-energy heavy ion collisions

The vorticity development is studied in the reaction plane of peripheral relativistic heavy ion reactions where the initial state has substantial angular momentum. The rotation effect and Kelvin Helmholtz Instability (KHI), lead to significant initial vorticity and circulation. This is also shown in an exact analytical fluid dynamic model, the conditions for the development of KHI for the QGP are also investigated. In low viscosity QGP the vorticity remains still significant at the time of freeze out of the system, even if damping due to the explosive expansion and the dissipation decreases the vorticity and circulation. The vorticity arises from the initial angular momentum in the reaction plane, and it is stronger than in the transverse plane, where only the random fluctuations lead to vorticity.

Speaker: Dujuan Wang (University of Bergen)

Poster Wang-poster-QM2014.pdf

16:30 Fluctuations in Relativistic Causal Hydrodynamics

Formalism to calculate the hydrodynamic fluctuations by applying the Onsager theory to the relativistic Navier-Stokes equation is already known. In this work, we calculate hydrodynamic-fluctuations in the framework of the causal hydrodynamics of M\"{u}ller, Israel and Stewart and the other related approaches. We show that expressions for the Onsager-coefficients and the correlation-functions have forms similar to the ones obtained by using the relativistic Navier-Stokes equation. However, spatio-temporal evolution of the correlation functions obtained using MIS and the other causal theories can be significantly different from the correlation functions obtained using the Navier-Stokes equation. Finally, as an illustrative example, we numerically evaluate the correlation-functions using the one-dimensional expanding boost-invariant (Bjorken) flows and compare the correlation-functions obtained using the various hydrodynamic approaches.

Speaker: Dr Ananta P. Mishra (Physical Research Laboratory, Ahmedabad)

Poster qm2014poster.pdf

16:30 FoCal, a high-granularity electromagnetic calorimeter development as a possible upgrade for the ALICE experiment

A forward electromagnetic calorimeter (FoCal) based on SiW technology is being considered as a possible upgrade to the ALICE detector. The main driving force behind this detector is the ability to measure direct photons in a so far unreachable part of phase space. It should thus provide unique information relevant for the study of the small-x structure of nucleons and nuclei and possible effects of gluon saturation, among many other interesting physics topics. To achieve this, the device should in particular feature an extremely high lateral granularity allowing gamma/pi0 discrimination out to very high momenta. The main option considered for the high granularity layers are CMOS pixel sensors. We will discuss the motivation and design principles of the proposed calorimeter and will then focus on the experience gained with a full CMOS-pixel calorimeter prototype. We will also discuss the status of photon identification algorithms to be used with such a detector.

Speaker: Thomas Peitzmann (University of Utrecht (NL))

16:30 Forward rapidity two-particle correlations in p--Pb collisions measured in ALICE

Two-particle correlation studies in high-multiplicity p--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$ have revealed a long-range correlation pattern underneath the expected jet correlations. This symmetric double-ridge pattern extends to large pseudorapidity difference. Long-range correlations were also observed in pp collisions with extreme multiplicity at LHC energies. The qualitative resemblance of the ridges in pp and p--Pb to flow-like correlations in Pb--Pb collisions still challenges our understanding of the small collision systems. Current explanations attribute the collective effects to initial state saturation and hydrodynamic behavior of dense matter created in the collisions. Saturation effects in p--Pb are expected to be enhanced in the low-x regime of the nucleus that can be probed at forward rapidities. The ALICE muon spectrometer with its forward pseudorapidity coverage can be used to detect charged tracks in the range $-4<\eta<-2.5$. Correlations between these forward tracks and particles detected at midrapidity are used to study the pseudorapidity dependence of the double ridge.

Speaker: Tim Schuster (Yale University (US))

Poster schuster_muh_QM2014_v5.pdf

16:30 Forward-backward multiplicity correlation in relativistic heavy-ion collisions in a superposition approach

Multiplicity correlations between distant forward and backward (FB) rapidity regions in relativistic heavy-ion collisions are examined in a superposition framework. Our three-stage approach incorporates the fluctuations of parton production in the early phase (modeled with the Glauber simulations), the effects of intermediate hydrodynamic evolution, and fluctuations in the production mechanism at freeze-out. Characterization of the three stages with several parameters leads to very simple relations between the statistical moments of the distributions of the initial sources and of the produced particles. Our study has a direct relevance for the interpretation of the upcoming results for the FB correlations at the LHC, allowing for an assessment of the statistical features of the state formed in the earliest stage of the reaction.

Speaker: Adam Olszewski (Jan Kochanowski University)

Poster olszewskiqm2014.pdf

16:30 Forward-backward multiplicity correlations in pp collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV

Forward-backward multiplicity correlations have been measured with the ALICE detector at the LHC in pp minimum bias collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV. The measurement is performed in the central pseudorapidity region ($|\eta| < 0.8$) for $p_{\mathrm{T}}>0.3$ GeV/$c$. The multiplicity correlation strength ($b_{\rm corr}$) was obtained using pairs of separate pseudorapidity and azimuthal windows and studied as a function of the separation distance between the windows in $\eta$ and $\varphi$, as well as of the size of the windows. A considerable increase of the correlation strength with the collision energy is found. Two types of contributions -- the short-range (SR) and the long-range (LR) -- are observed. The energy dependence of $b_{\rm corr}$ is found to be weak for the SR component and strong for the LR component. The $b_{\rm corr}$ is also studied in different transverse momentum intervals, which have the same mean multiplicity. It is found that both SR and LR contributions to $b_{\rm corr}$ increase with increasing minimum threshold of $p_{\mathrm{T}}$. The results are compared to PYTHIA and PHOJET Monte Carlo event generators and to the string-based empirical model.

Speakers: Igor Altsybeev (St. Petersburg State University (RU)), Sudipan De (Department of Atomic Energy (IN))

Poster FB_mult_corr_pp_ALICE_poster_QM2014_Altsybeev_I.pdf

16:30 Fragmentation of jets into hadrons with strangeness in Pb-Pb collisions in ALICE at the LHC

The research programme of the ALICE experiment at the LHC focuses on studies of the quark-gluon plasma, a state of matter where quarks and gluons are deconfined. The measurement of jets originating from the fragmentation of hard-scattered partons in the early phases of a nuclear collision allows one to study parton energy loss in the hot and dense medium and provides constraints on theoretical predictions. Measuring yields of ${\rm K_s^0}$, ${\Lambda}$ and $\overline{\Lambda}$ down to low momenta within jet cones can help to disentangle contributions from fragmentation and other hadronisation mechanisms such as parton recombination and coalescence. In this poster we present the first results for ${\rm K_s^0}$, ${\Lambda}$ and $\overline{\Lambda}$ production associated with charged jets in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}} = 2.76$ TeV. Neutral strange baryons and mesons are reconstructed from their topological decays into charged particles measured in the ALICE central tracking detectors. A detailed systematic study of the strange-particle reconstruction efficiency in jet cones and the uncertainties related to jet energy resolution are discussed. The analysis is performed in different centrality classes and the results are compared with inclusive particle production.

Speakers: Alice Zimmermann (Ruprecht-Karls-Universitaet Heidelberg (DE)), Vit Kucera (Acad. of Sciences of the Czech Rep. (CZ))

Poster poster_final.pdf

16:30 Frame independent formulation of energy loss in evolving bulk medium

The PHENIX Collaboration has argued that azimuthal angle dependent pi0 suppression in Au+Au at RHIC poses a challenge for perturbative QCD energy loss models. Recent work by Betz and Gyulassy on the other hand claims simultaneous reproduction of this set of observables with simple pQCD-motivated energy loss formulas, in contrast with our earlier finding that realistic transverse expansion strongly suppresses elliptic flow. We resolve the apparent contradiction via a study that contrasts different bulk medium evolution models (based on hydrodynamics and covariant transport) combined with different implementations of Djordjevic-Gyulassy-Levai-Vitev radiative energy loss for light partons and heavy quarks. A key new ingredient relative to earlier dE/dL and (D)GLV studies is that we pay special attention to formulate energy loss in a way that results do not depend on the calculational frame. We find that covariant formulation accentuates the interplay between bulk medium evolution and parton energy loss, and show how this affects light hadron and heavy flavor anisotropic flow.

Speaker: Denes Molnar (Purdue University)

Poster DekeSun+DenesMolnar_poster_QM2014.pdf

16:30 Freeze-out parameters for the Large Hadron Collider

We explore various moments of conserved charges that can act as a freeze-out thermometer at large collision energies. We present the continuum extrapolated lattice results of the Wuppertal-Budapest collaboration for these candidates and discuss further implications to our understanding of the QCD transition. We compare our results to the expectations based on the hadron resonance gas model.

Speaker: Szabolcs Borsanyi (University of Wuppertal)

Poster poster.pdf

16:30 Freeze-out state from analysis of transverse momentum spectra in Pb+Pb collisions at 2.76 ATeV

We analyse identified hadron spectra in transverse momentum with the help of blast-wave model. Our approach properly includes all resonance decays contributing to hadron production. It is shown that there is no window in the transverse momentum where this contribution can be safely neglected in order to use simpler analytical formulas in the fit procedure. Based on the comparison of theoretical results to data we identify the fiducial range for the fit. The fit is also performed on Lambda's, Xi's and Omega's and the possibility of a different freeze-out time for these species is discussed. The freeze-out temperatures and transverse velocities for different centralities are compared with previously published ALICE results and the values from RHIC.

Speaker: Ivan Melo (University of Zilina (SK))

Poster QMposter_Melo.pdf

16:30 From the Quark Gluon Plasma to Strongly Coupled Conformal Theories

We discuss our results on the thermal phase transition in color $SU(3)$ QCD with a large number $N_f$ of fundamental fermions using lattice gauge theory. We study the dependence of the critical temperature $T_c$ of the transition and of the coupling at $T_c$ on $N_f$. These results are used to investigate precursory effects of conformality associated with the emergence of a non-trivial fixed point at large $N_f$ and to show how real quark gluon plasma is smoothly connected to a strongly coupled system at zero temperature.

Speaker: Mr Tiago Nunes da Silva (University of Groningen)

16:30 G2 gauge theories as a tool to understand the QCD phase diagram

G2 gauge theories are variants of QCD and Yang-Mills theory where the gauge group SU(3) has been replaced by the exceptional group G2. These theories permit to study aspects of QCD which are hard to access otherwise. Especially, these theories are accessible to lattice simulations at finite density, and it is thus possible to determine the phase diagram completely. Because G2 QCD has also fermionic baryons, it is possible to search for hadronic Fermi surface effects, which are conjectured to be important for neutron stars. Also, G2 gauge theories have a trivial center, and it is therefore possible to asses the importance of the center structure to QCD. In this talk, the basic outline of these theories will be given, and it will be shown how similar they are to ordinary QCD. Then briefly some pertinent aspects of the phase diagram of these theories will be introduced. A more detailed look at the phase diagram, particular at intermediate densities, will be presented in a second talk.

Speaker: Axel Maas (University of Jena)

Poster qm.pdf

16:30 Generic framework for anisotropic flow analyses with multi-particle azimuthal correlations

We present a new generic framework which enables exact and fast evaluation of all multi-particle azimuthal correlations. The framework can be readily used along with a correction framework for systematic biases in anisotropic flow analyses due to various detector inefficiencies. A new recursive algorithm has been developed for higher order correlators for the cases where their direct implementation is not feasible. We propose and discuss new azimuthal observables for anisotropic flow analyses which can be measured for the first time with our new framework. Effects of finite detector granularity on multi-particle correlations are quantified and discussed in detail. We point out the existence of a systematic bias in traditional differential flow analyses which stems solely from the applied selection criteria on particles used in the analyses, and is also present in the ideal case when only flow correlations are present. Finally, we extend the applicability of our generic framework to the case of differential multi-particle correlations.

Speaker: Alexander Hansen (University of Copenhagen (DK))

Poster poster_final3.pdf

16:30 Ghosts in Nonequilibrium Quark-Gluon Plasma

The quark-gluon plasma at the early stage of relativistic heavy-ion collisions is out of equilibrium. The Keldysh-Schwinger formalism provides a natural framework to describe such a plasma, in particular when the plasma is weakly coupled and perturbative methods are applicable. However, a perturbative computation of various QCD characteristics requires Faddeev-Popov ghosts to cancel unphysical degrees of freedom which are present in a wide class of covariant gauges. The question thus arises how to introduce the ghosts for non-equilibrium QCD. Using the functional methods, we derive a relation analogous to the Slavnov-Taylor identity which expresses the ghost propagator of the Keldysh-Schwinger formalism through the gluon one. Then we show that the ghost propagator obtained in this way allows one to construct a gauge invariant perturbative expansion of various characteristics of non-equilibrium quark-gluon plasma.

Speaker: Alina Czajka (Jan Kochanowski University)

Poster poster-ghosts.pdf

16:30 Global alignment methods of the inner silicon tracker (HFT) of the STAR experiment at RHIC

We present an overview of two global alignment procedures developed for the Heavy Flavor Tracker[1] (HFT), the new silicon upgrade detector of STAR experiment at RHIC. Both methods are iterative minimization techniques and use as input the hit residual information from primary tracks reconstructed by the STAR TPC. One relies on a factorization of the alignment steps and uses histogramming techniques to improve the robustness of the minimization, while the other is based on a global $\chi^2$ minimization technique developed for the CMS detector[2]. The methods’ performance was extensively tested using simulations with mis-alignments. Here we present the basic elements of the methods, their estimated performance characteristics and also their application to data collected from a PIXEL prototype beam test in 2013. [1]:HFT proposal: http://rnc.lbl.gov/~wieman/hft_final_submission_version.pdf [2]:The HIP algorithm for track based alignment and its application to the CMS detector, V. Karimaki et. al., CMS note 2006/018

Speaker: Mr Michael Lomnitz (Kent State University)

Poster AlignmentPoster_QM2014.pdf

16:30 Gluon Bremsstrahlung of Charm Quark \& Charm Quark Equilibrium Distribution Function

The effect of soft gluon bremsstrahlung off the charm quark on different transport coefficients like drag, transverse and longitudinal diffusion of charm has been observed while it is propagating inside Quark Gluon Plasma. The elastic collision of charm with the medium particles and the gluon radiation are seen to contribute in comparable magnitudes while evaluating of the transport coefficients. However, it is noticed that the ultimate shape of the charm quark distribution function after it has come to equilibrium remains more or less unaffected by the radiation of charm. We also observe that the shear viscosity to entropy ratio of the quark gluon plasma (QGP) is closer to the experimentally extracted value when the gluon radiation by the charm quark is included

Speaker: Surasree Mazumder (Variable Energy Cyclotron Centre, Kolkata)

Poster QM_2014_surasree.pdf

16:30 Hadron-Quark Crossover as a Possible Resolution of Hyperon Crisis in Massive Neutron Stars

Recent observations of two solar-mass neutron stars bring a serious conflict between the stiff equation of state (EOS) required from the observations and the soft EOS with hyperons required from theory. We call this problem the "Hyperon Crisis". We propose a possible resolution of this problem from the point of view of the smooth crossover between the hadronic matter with hyperons and the strongly interacting (2+1)-flavor quark matter at around 3 times the normal nuclear matter density. The sound velocity is found to increase in the crossover region, which leads to a stiff EOS and hence to two solar-mass neutron stars with reasonable radius of about 11-12 km [1,2]. Our idea is in sharp contrast to the conventional approach of the first-order hadron-quark transition where the EOS always becomes soft. The above conclusion is robust in the sense that the qualitative results do not depend on the different choices of hadronic EOS nor the different ways of interpolation between the hadronic EOS and quark EOS. Also, we found that the three-body forces acting among nucleons and hyperons play essential role for the onset density of strangeness mixing and the cooling of neutron stars, while the effect of the color superconductivity does not affect the above conclusion. Our analyses strongly indicate the necessity of strongly interacting quark matter inside massive neutron stars. [1] K. Masuda, T. Hatsuda and T. Takatsuka, ApJ 764, 12 (2013) [2] K. Masuda, T. Hatsuda and T. Takatsuka, PTEP 073D01 (2013)

Speaker: Mr Kota Masuda (Univ. of Tokyo / RIKEN)

Poster QM2014-masuda.pdf

16:30 he second order hydro-coefficient $\kappa_t$ and antiscreening of QED and QCD plasmas from lattice QCD

The static forces between electric charges and currents are modified at the loop level by the presence of a plasma. While electric charges are screened, currents are not. This can be understood as medium-induced ‘antiscreening’ of the Ampere force and enters the constitutive equation of the electric current at second order in a ‘hydrodynamic’ description as the quantity $\kappa_t$. We investigate these effects and this second order ’hydro-coefficient’ quantitatively using non-perturbative simulations of QCD with two light degenerate flavors of quarks.

Speaker: Dr Anthony Francis (Helmholtz Institut Mainz)

Poster QM2014-poster.pdf

16:30 Heavy flavor muons at forward rapidities in $\sqrt{s_{NN}}=200$ GeV p+p and Cu+Au collisions

The dynamics of heavy flavor production and suppression in $A$+$A$ collisions play an important role in unraveling the properties of the quark-gluon plasma produced at RHIC. The related observables offer direct insight into strongly-coupled nature of the medium. It has also become increasingly apparent that the production and suppression in the absence of a hot medium need to be studied in detail, via comprehensive measurements in $p$+$p$, $p$($d$)+$A$, and $A$+$A$ collisions of varying size and energy at RHIC and the LHC. I will present heavy flavor invariant yields and nuclear modification factors at forward rapidity in the 2012 $\sqrt{s_{NN}}=200$ GeV $p$+$p$ and Cu+Au collisions recorded at PHENIX and discuss their implications for our current understanding of heavy flavor production.

Speaker: Matthew Wysocki (Oak Ridge National Lab)

Poster wysocki_poster.pdf

16:30 Heavy Quark azimuthal correlations in proton-proton and nucleus-nucleus collisions.

I will present very recent results on heavy-quark (and meson) azimuthal correlations in proton-proton and nucleus-nucleus collisions at LHC energies. We simulate the $c-\bar{c}$ and $b-\bar{b}$ pair initial creation with a perturbative QCD approach (POWHEG+PYTHIA). Successively we study the propagation of the heavy quarks in the plasma with the relativistic Langevin equation and, eventually, their hadronization in the medium. By applying suitable cuts on the transverse momentum of one (or both) quarks of a pair, we show that it is possible to select a specific "region" of the strongly interacting medium (the hot core or the colder rim) and, therefore, to study its properties.

Speaker: Marzia Nardi (INFN)

Slides Poster_QM14.pdf

16:30 Heavy Quark Interactions with the Medium as Measured with Electron-Hadron Correlations in $Au+Au$ Collisions in STAR

Measurements of heavy flavor $R_{AA}$ have shown a large suppression in central heavy ion collisions, indicating the importance of both gluon radiation and collisional energy loss in models of heavy quark propagation. There is still considerable uncertainty around the energy loss mechanisms of heavy quarks in QGP: the relative contribution of radiative and collisional interactions to the energy loss of heavy quarks as well as the response of the medium to heavy quark propagation are both open questions. Two particle correlations from heavy flavor jets are a unique tool to investigate interactions with QGP, as away side correlations in central events should show modifications as compared to measurements in peripheral bins and $p+p$ collisions. High $p_{T}$ non-photonic electrons serve as a proxy for heavy flavor mesons coming from heavy ion collisions and allow us to tag heavy flavor jets. These electrons' correlations to associated hadrons could give insight into the interactions between charm and bottom quarks and the medium. The away side will contain information both from the decay of any associated away side meson as well as interaction of the away side jet with the bulk. The high statistics from STAR Run 11 allow us to construct correlations across a range of centralities and particle $p_{T}$. We present measurements of correlations of non-photonic electrons to hadrons in high tower triggered $\sqrt{s} = 200$ GeV $Au+Au$ data from STAR, and will show comparisons to theoretical models for heavy quark correlations in QGP.

Speaker: Jay Dunkelberger (UCLA)

Poster QMposter_FINAL.pdf

16:30 Heavy quark pair production and parton saturation in pA collisions at the LHC

Understanding of the initial state effects on heavy ion collisions is indispensable for quantifying the subsequent hot medium effects in the observables. Heavy quark pair production in proton-nucleus (pA) collisions provides us with a unique opportunity to probe the gluons at small Bjorken's x in the heavy target nucleus, where the so-called parton saturation effect becomes important for particle production. We have studied heavy quark pair production in pA collisions within the color glass condensate (CGC) framework [1] by adopting numerical solutions for gluon distributions obtained from the Balitsky-Kovchegov equation with running coupling corrections [2, 3]. We report our numerical results on J/psi and D productions in pA collisions at the RHIC and LHC energies [4, 5], and discuss possible extension our calculation in light of recent experimental data. References: 1. J.-P. Blaizot, F. Gelis, and R. Venugopalan, Nucl. Phys. A743, 57 (2004). 2. I. Balitsky, Phys. Rev. D75, 014001 (2007). 3. Yuri V. Kovchegov and H. Weigert, Nucl.Phys. A784, 188 (2007). 4. H. Fujii and K. Watanabe, Nucl. Phys. A915, 1 (2013). 5. H. Fujii and K. Watanabe, Nucl. Phys. A920, 78 (2013).

Speaker: Kazuhiro Watanabe (The University of Tokyo)

Poster QM2014-K.Watanabe.pdf

16:30 Heavy Quarks and Mesons at Finite Chemical Potential in Gauge/Gravity Duality

We study the properties of heavy quarks as probes of strongly coupled plasmas with non-zero chemical potential by means of deformations of the gauge/gravity (AdS/CFT) duality. We compute the screening distance of a heavy quark-antiquark pair, its free energy, and the running coupling, as well as the drag force experienced by a single quark in large classes of models. The screening distance and the free energy exhibit some insensitivity concerning the choice of model and deformation, pointing to strong-coupling universal behavior that depends only weakly on the microscopic details. Thus, our results may be relevant for modeling heavy quarkonia traversing a quark-gluon plasma at finite net baryon density, and their suppression by melting.

Speaker: Mr Andreas Samberg (Institute for Theoretical Physics, Heidelberg University)

Poster Poster_Quark_Matter_2014_Samberg.pdf

16:30 Heavy-flavor muon production at forward rapidity in $d+$Au collisions at $\sqrt{s_{NN}}=200$ GeV

The measurement of single muons from semi-leptonic decay of mostly $D$ an $B$ mesons is a well developed method to study heavy quark production at forward rapidity at PHENIX experiment. Such measurement in $d+$Au collisions in wide rapidity ranges is essential to study initial-state cold nuclear matter effects, e.g. modification of parton distribution function, $p_{T}$ broadening, and energy loss, on heavy quark production. In addition, comparison to $J/\psi$ results may provide a key constraint to understand the nuclear break-up of quarkonia systems. In this poster, we will present the PHENIX heavy-flavor muon measurements at forward and backward rapidity regions at $\sqrt{s_{NN}}=200~{\rm GeV}$ and comparison with theoretical models to interpret the results.

Speaker: Sanghoon Lim (Yonsei University)

Poster QM2014_poster_shlim_final.pdf

16:30 Heavy-meson diffusion in hadronic matter

Heavy mesons can be reconstructed in high-energy ion collisions from the detected electrons coming from their semileptonic decays. Due the their large mass ($m_D,m_B \gg \Lambda_{QCD}$) they carry important information about the initial stages of the heavy-ion collision. In particular, the $D$-meson $R_{AA}$ and $v_2$ have already been extracted in the RHIC and the LHC. These out-of-equilibrium observables strongly depend on the heavy-meson transport properties. We present theoretical results on the transport coefficients of $D$ and $B$ mesons in a hadronic medium as a function of temperature and baryochemical potential. In particular, we focus on the diffusion coefficients, drag force, energy loss and the heavy-meson relaxation time. To compute them, we implement a transport equation in the Fokker-Planck limit applied to a thermal medium composed by $\pi$, $K$, $\bar{K}$, $\eta$, $N$ and $\Delta$ baryons, with whom the $D$ and $B$ mesons can interact. The (elastic+inelastic) interaction is extracted from effective field theories consistent with chiral and heavy-quark spin symmetries. We incorporate a unitarization method to exactly restore the $S$-matrix unitarity and to account for a set of dynamically generated resonances ($D_0$, $D_1$, $B_0$, $B_1$, $\Lambda_c$, $\Sigma_c$, $\Lambda_b$, $\Sigma_b$...) that are systematically taken into account in the transport computation. We focus our investigations to physics at vanishing net-baryon density (for physics at the RHIC and the LHC) but also for physics at finite baryochemical potential (for the future FAIR conditions).

Speaker: Dr Juan Torres-Rincon (Institut de Ciencies de l'Espai)

16:30 Heavy-quark diffusion at LHC, RHIC, and FAIR within a UrQMD-hydrodynamical hybrid model

Heavy charm and bottom quarks provide an important probe of the transport properties of the quark-gluon plasma, created in heavy-ion collisions at the Large Hadron Collider (LHC). They are produced in the early hard collisions and then interact with the hot and dense medium, consisting of light quarks and gluons, undergoing a phase transition to a hot and dense hadron gas. Using a hybrid model of Ultrarelativistic Molecular Dynamics (UrQMD) and 3D hydrodynamics to simulate the evolution of the hot and dense medium, we describe heavy-quark interactions with the medium in terms of a Fokker-Planck/Langevin framework with drag and diffusion coefficients based on a Dirac-Brueckner evaluation of the in-medium scattering-matrix elements using lattice QCD heavy-quark potentials for elastic light-heavy-quark scattering or a phenomenological resonance-scattering model based on chiral and heavy-quark effective theory to evaluate the nuclear modification factor, R_AA, and elliptic flow v_2 of D- and B-mesons and "non-photonic electrons" from their semileptonic decays. The results are compared with recent data from the ALICE collaboration on R_AA and elliptic flow of single electrons, muons, and D-mesons, data on non-photonic electrons from the PHENIX Collaboration. We also study the impact of the corresponding medium modifications of D and $\overline{\mathrm{D}}$ mesons on the contribution of their correlated decay to the dilepton signal. This is particularly interesting, because in the intermediate $\ell^+ \ell^-$-invariant-mass region, $M_{\phi} < M_{\ell^+ \ell^-} < M_{J/\psi}$ this is the dominant dilepton source competing with "thermal radiation" from the QGP. Finally we use the same HQ-diffusion model for predictions about similar signals of $\mathrm{D}$ and $\overline{\mathrm{D}}$ mesons to be expected at the future CBM experiment at FAIR.

Speaker: Hendrik van Hees (Goethe University Frankfurt and FIAS)

Poster qm14-poster.pdf

16:30 High-$p_T$ $J/\psi$ production in $U+U$ collisions at STAR

The Relativistic Heavy-Ion Collider (RHIC) is built to search for the QGP in laboratory through the high energy heavy ion collisions. Suppression of the $J/\psi$ production due to color screening of the $c\overline{c}$ binding potential in the deconfined medium has been proposed as a signature of the QGP formation. High-$p_T$ $J/\psi$ measurements in $Au+Au$ collisions at RHIC published recently by the STAR collaboration show significant suppression in the most central collisions. Since secondary production via $c\overline{c}$ recombination and so called cold nuclear matter effects are small at high $p_T$, these results point to the color screening features. The energy density is expected to be on average about 20% higher in $U+U$ collisions than in $Au+Au$ collisions, therefore the $J/\psi$ measurement in $U+U$ collisions at high $p_T$ can provide new insight in the study of color screening features for charmonium. In this presentation we will report the status of the analysis of mid-rapidity $(|y|<1)$ $J/\psi\rightarrow$$e^{+}e^{-}$ production in $U+U$ collisions at $\sqrt{s_{NN}} = $193 GeV at STAR using RHIC year 2012 data triggered with the Barrel Electromagnetic Calorimeter.

Speaker: Guannan Xie (for the STAR Collaboration)

Slides GuannanXie_QM14_UU_Poster_HF_V8.pdf

16:30 High-$p_{T}$ non-photonic electron production in p+p collisions at $\sqrt{s}$=200 GeV

Measurement of heavy flavor production in proton-proton collisions tests the validity of the pQCD frameworks for the heavy quark production. It also provides a baseline for the interpretation of heavy flavor production in nucleus-nucleus collisions. We present an improved measurement of non-photonic electron (NPE) production at high transverse momentum (2.5<$p_{T}$<12 GeV/c) in proton-proton collisions at $\sqrt{s}=$200 GeV. The result is based on about 24 pb$^{-1}$ data recorded during the year 2012 run by the STAR experiment at the Relativistic Heavy Ion Collider. The measured NPE production cross-section will be compared to pQCD model calculations [1]. [1] R.E. Nelson, R. Vogt and A.D. Frawley, Phys. Rev. C 87, 014908 (2013).

Speakers: Mr Xiaozhi Bai (University of Illinois at Chicago), Prof. Zhenyu Ye (University of Illinois at Chicago)

Poster QM14poster_NPE_Xiaozhi_update.pdf

16:30 Higher moments of multiplicity distributions in nuclear collisions at relativistic energies

Heavy ion reactions at ultrarelativistic energies provide information on strongly interacting matter under extreme conditions. In these collisions a large number of particles of different types is produced. Current understanding of such collisions suggest that the production of a QGP phase in relativistic heavy ion collisions could produce significant event-by-event correlations and fluctuations in transverse momentum, multiplicity, etc. Therefore it is important to analyze fluctuations of multiplicities (net-protons, net-strangeness, total protons) for different energies and centralities and search for anomalous behaviour due to a phase transition. The multiplicity distributions of different types of particles produced in simulated Au+Au collisions using different theoretical models at energies ranging from 2 – 200 AGeV were analyzed and the moments of the distributions were calculated. Model results can be used to provide a baseline for the phase transition and QCD critical point search. The centrality and beam energy dependence of the moments of simulated multiplicity distributions will be shown and discussed.

Speaker: Dr Catalin Ristea (Faculty of Physics, University of Bucharest, Institute of Space Science, Magurele)

16:30 Higher order asymmetries with exact hydrodynamics

The time evolution of the medium created in heavy ion collisions can be described by hydrodynamical models. After expansion and cooling, the hadrons are created in a freeze-out. Their distribution describes the final state of this medium. Exact hydrodynamics provides a tool to have an analytic handle on the connection between the initial state, the dynamic parameters of the system and the observables. Usually azimuthal or elliptical symmetry is assumed in the transverse plane, as these are simple to handle and represent geometries to yield realistic observables like spectra, Bose-Einstein correlation functions and elliptic flow. However, nuclei contain a finite number of nucleons, are thus (on an event-by-event basis) not spherically symmetric. This results in an event-by-event fluctuating initial condition, which gives rise to higher order flow coefficients, with respect to higher order reaction planes. Correlation radii can also be measured with respect to higher order reaction planes, their comparison to higher order flow coefficients gives insight into the dynamics of the system. In this work we show the first exact analytic solutions of relativistic hydrodynamics [Ref1,Ref2] that assume higher order asymmetries (see Fig. [1]) and thus give realistic higher order flow coefficients (see Fig. [2]). Besides presenting the first such model, we also show a comparison of our results to various measured hadronic observables. Ref1: M. Csanád, talk at the IX Workshop on Particle Correlations and Femtoscopy (presented by T. Csörgő) https://indico.cern.ch/event/248321/session/12/contribution/33/material/slides/ Ref2: A. Szabó, talk at the 2013 Zimányi School https://indico.cern.ch/event/286124/session/3/contribution/11/material/slides/ Fig 1.: http://csanad.web.elte.hu/phys/v3sol/vnplot3.png Fig 2.: http://csanad.web.elte.hu/phys/v3sol/phenix3040.png

Speaker: Mate Csanad

Poster csanad_qm14_hidro_poster.pdf

16:30 Higher order fluctuations of strangeness and flavor hierarchy

In recent years, the study of fluctuations of conserved charges has received increasing attention: they turned out to be a promising tool to study the deconfinement phase transition of QCD, the existence of a critical point in the phase diagram and, more recently, the freeze-out conditions in heavy-ion collisions (HICs). Recent lattice QCD simulations and phenomenological models have found first indications for a different transition-temperature for strange and light quarks. The study of the higher order moments of the strange particle distributions measured in HICs would be very useful to clarify this issue. Preliminary results on the moments of net-charged kaons have been presented by the STAR collaboration, with experimental kinematic cuts but still without corrections due to finite acceptance in the detectors. Combinations of such moments are related to volume-independent ratios of higher order cumulants, which can be calculated in the Hadron Resonance Gas (HRG) model. I present results for higher order fluctuations of strangeness in the HRG model, including different combinations of stable strange hadrons, resonance feed-down corrections, kinematic cuts, thus getting as close as possible to the future HIC strangeness fluctuation measurements.

Speaker: Dr Paolo Giuseppe Alba (University of Turin)

Poster poster_ALBA.pdf

16:30 Hough transform for charged particle tracking in CMS

The Hough transform is a pattern recognition technique well suited for identifying charged particle trajectories, which is used in several high-energy and heavy-ion physics experiments. The CMS experiment currently uses a combinatorial track-following method for both proton and heavy-ion collisions. In this poster we explore the possibility of using the Hough transform method in heavy ions. Such a method may improve the timing of the track reconstruction, particular for tracks with large impact parameter with respect to the primary vertex.

Speaker: Stanislav Lisniak (Ecole Polytechnique (FR))

16:30 Hydrodynamical evolution with energy and momentum feeding during the fireball expansion

We perform event-by-event (3+1)-dimensional ideal hydrodynamic simulation with source terms that describe energy and momentum deposition from hard partons into expanding medium and study interplay of perturbations due to various number of leading particles propagating in various directions. This type of perturbations differs qualitatively from simulations with fluctuating initial conditions by the fact that it perturbes the medium continuously during the evolution and not just at its beginning. For comparison, the time evolution of various types of eccentricities is examined for three types of scenarios: smooth IC, smooth IC with hot-spots and smooth IC with evolving hard partons. We study how the differences between all these types of scenarios show up in excentrities of different orders.

Speaker: Martin Schulc (Czech Technical University (CZ))

Poster Poster.pdf

16:30 HypHI project: Final results of the study of hypernuclei in the reaction $^{6}$Li+$^{12}$C at 2$A$GeV

The HypHI collaboration aimed to demonstrate the feasibility of the spectroscopy of hypernuclei produced in heavy-ion and rare isotope induced reactions. A first experiment was performed on October 2009 with a $^{6}$Li beam bombarded on a $^{12}$C carbon fixed target at 2 $A$GeV. In a second experiment in March 2010, a different beam nucleus of $^{20}$Ne at 2 $A$GeV was employed in a similar setup. The experimental approach was developed to measure and study hypernuclei produced in the projectile rapidity region. Such $\Lambda$-hypernuclei are assumed to be obtained by the coalescence between $\Lambda$ hyperon produced in the mid rapidity region of the participant zone and projectile spectator fragments from the collision between the beam and target nuclei. Final results of the first experiment $^{6}$Li+$^{12}$C at 2$A$GeV will be presented, demonstrating that $\Lambda$ hyperon, $^{3}_\Lambda$H and $^4_\Lambda$H hypernuclei were observed by performing the vertex reconstruction and the measurement of their invariant mass. Their lifetimes were extracted and were in good agreement with the world data. A review of the lifetime of these light hypernuclei was performed and showed that their measured lifetimes are significantly shorter than the $\Lambda$ lifetime which bring new interrogation about their fundamental structures. As well, the evidence of a bound state of two neutrons and one $\Lambda$ hyperon, $^3_\Lambda$n, will be presented. It corresponds to the first observation of a neutral bound state. Finally the estimation of the production cross section of the observed $\Lambda$ hyperon and hypernuclei will be shown, corresponding the first experimental estimation of those observables. These estimations will be useful for constraining theoretical models of the hypernuclear production, and an insight on these implications will be given. Future plans to study exotic proton and neutron rich hypernuclei will conclude the presentation.

Speaker: Dr Christophe Rappold (Justus-Liebig-Universit\"at Giessen & GSI Helmholtz Centre for Heavy Ion Research)

Poster PosterQM2014_crappold.pdf

16:30 Identified charged hadron spectra and ratios in PHENIX

PHENIX has recently reported [Phys. Rev. C88 024906] measurements of identified charged hadron spectra and ratios in Au+Au and d+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Identified hadrons are an important probe of both hot and cold nuclear matter. The intermediate $p_T$ region, 2--5~GeV/c, is of particular interest. In Au+Au collisions, the production of mesons is suppressed in this $p_T$ region relative to that in p+p collisions, while the production of baryons is nearly unmodified. On the other hand, in d+Au collisions, the meson production exhibits a slight enhancement in this $p_T$ region while the baryon production exhibits a much stronger enhancement. In this poster, the $p_T$ spectra and ratios of identified charged hadrons $\pi^{\pm}$, $K^{\pm}$, $p$, and $\bar{p}$ in 5 different centrality classes for each collision species will be presented. Implications for particle production will be discussed.

Speaker: Ron Belmont (Wayne State University (US))

Slides poster.pdf

16:30 Identified particle femtoscopy in Pb-Pb collisions with ALICE at the LHC

Two-particle momentum correlations carry important information about the space-time characteristics of the particle emission region. Femtoscopic correlations at low relative momentum arise from quantum statistics (for identical particle pairs) and final-state interactions (for both identical and non-identical pairs) and are used to probe the homogeneity lengths of the emitting source. Hydrodynamic models predict a decrease of these homogeneity lengths with increasing pair transverse mass ($m_{\rm T}$), which has been confirmed by pion analyses. Femtoscopic analyses of heavier particles are able to extend the $m_{\rm T}$ range and thus further constrain theoretical models. Femtoscopic correlations are also important for studying two-particle systems whose scattering interaction is not well-known. They can be used to extract information about the interaction, such as scattering lengths and effective ranges. We present measurements of two-particle femtoscopic correlations of several identical and non-identical systems of mesons and baryons measured by ALICE in $\sqrt{s_{\rm NN}}$ = 2.76 TeV Pb-Pb collisions. One-dimensional radii ($R_{\rm inv}$) and $\lambda$ parameters for various particle types are extracted, with which an approximate $m_{\rm T}$-scaling is seen beyond the range of previous pion analyses. Fit parameters are also compared with theoretical model predictions.

Speaker: Hans Beck (Johann-Wolfgang-Goethe Univ. (DE))

Poster QM14Poster_v7.pdf

16:30 Identified particle production for $p+p$ collisions in $\sqrt{s}$ = 62.4 GeV at STAR

It is important to study the particle production as a function of both transverse momentum ($p_{T}$) and particle species which provide crucial input for modeling of hadronic interactions and the hadronization process in high-energy collisions [1]. In this contribution, we will present the results on $\pi^{\pm}$, $K^{\pm}$, $p$ and $\bar{p}$ in $p+p$ collisions at $\sqrt{s}$ = 62.4 GeV from STAR experiment at the Relativistic Heavy Ion Collider. The results are obtained for the midrapidity region in the range $\mid{y}\mid < 0.1$. Charged hadrons are identified by using specific ionization energy loss at the low momentum region (up to 1.10 GeV/c) with STAR's Time Projection Chamber detector [2,3]. We will present the final corrected $p_{T}$ spectra, particle yields and various particle ratios. The results will be compared with different models namely PYTHIA and PHOJET. References: [1] H. Satz, $\it{Rep. Prog. Phys.}$ 63 (2000) 151. [2] H. Bichsel, $\it{Nucl. Instrum. Meth. A}$ vol. 562, (2006) 154-197. [3] B. I. Abelev et al., [STAR Collaboration], $\it{Phys. Rev. C}$ 79 (2009) 34909.

Speaker: Shikshit Gupta (University of Jammu)

Poster Final_QM14_poster_shikshit.pdf

16:30 Identified-identified two-particle correlations and quantum number conservation in p-p, p-Pb and Pb-Pb collisions at LHC energies

Unidentified two-particle correlations are widely pursued at RHIC and LHC to investigate particle production and hadronization mechanisms as well as collective effects. Two-particle correlations with identified trigger and identified associated particles give information on quantum number conservation and the flavour balance during parton fragmentation and hadronization, however their detailed measurement at LHC is just started. We present a systematic study of two-particle correlations with identified trigger and identified associated particles at LHC energies with the state of art LHC era Monte Carlo generators. The identified-identified two-particle correlation studies of bulk particles: charged pions, kaons and protons reveal interesting trigger-hadron dependent splitting of the associated identified hadron spectra in all collision systems. Furthermore, the identified correlation functions show change in the identified trigger-hadron dependent evolution with transverse momenta compared to unidentified correlation functions. The source of the splitting effect and their evolution from p-p and p-Pb to Pb-Pb collisions will be discussed.

Speaker: Gyula Bencedi (Hungarian Academy of Sciences (HU))

Poster GBencedi_QM2014_poster_final_20140519_0005.pdf

16:30 Inclusive J/$\psi$ and $\psi$(2S) production at forward rapidity in pp collisions with ALICE at the LHC

The ALICE collaboration has studied inclusive J/$\psi$ and $\psi$(2S) production at forward rapidities in pp collisions at $\sqrt{s} = 7$ TeV and 8 TeV with integrated luminosity $\mathcal{L}_{\rm int}$ = 1.35 pb$^{-1}$ and 584 nb$^{-1}$, respectively. The integrated and differential production cross-sections of J/$\psi$ and $\psi$(2S) will be presented. The comparison with the LHCb results and comparison with the theoretical predictions at $\sqrt{s} = 7$ TeV will also be shown. The values of $\psi$(2S)/J/$\psi$ production ratio in pp collisions at $\sqrt{s} = 2.76$, 7 and 8 TeV will be reported.

Speaker: Biswarup Paul (Saha Institute of Nuclear Physics (IN))

Poster 2014-May-16-conferencefile-QM14_poster_v5(1).pdf

16:30 Inclusive Jet Spectra in p-Pb Collisions at ALICE

Jet suppression has been observed in central heavy-ion collisions. This suppression is attributed to partonic energy loss in the Quark-Gluon Plasma (QGP) formed in such collisions. However, this measurement is influenced by all stages of the collision. It is expected that in p-Pb collisions the same initial conditions occur as in Pb-Pb collisions without creating a QGP, allowing any cold nuclear matter effects to the jet spectra to be quantified. Inclusive jet spectra in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV measured by ALICE will be presented. Jets are reconstructed via the anti-$k_{\rm T}$ algorithm with different resolution parameters by combining charged tracks measured in the ALICE tracking system with the neutral energy deposited in the electromagnetic calorimeter. The spectra can be used to determine a nuclear modification factor $R_{\rm pPb}$ while the jet profile in p-Pb is studied by dividing spectra measured with different resolution parameters and comparing to the same ratio measured in pp collisions. The multiplicity dependence of the spectra in p-Pb collisions is also explored.

Speaker: Megan Elizabeth Connors (Yale University (US))

Poster connors_pPbjetPosterQM2014v10.pdf

16:30 Inclusive Spectrum of Reconstructed Charged Jets in Central Au+Au Collisions at $\sqrt{s_{NN}}$=200 GeV by the STAR Experiment

Jet interaction in the medium provides sensitive observables to study properties of the hot and dense nuclear matter created in heavy-ion collisions. However, due to the large and fluctuating background, full jet reconstruction in heavy-ion collisions is an extremely challenging task. In this poster, we present a new measurement of the inclusive spectra of reconstructed jets in central Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV by the STAR collaboration at RHIC. Jets are reconstructed using charged tracks from the time projection chamber. We utilize an experimental technique in which jet reconstruction is stable against the emission of an additional soft hadron, even in the high-multiplicity environment. In this technique the large combinatorial background is suppressed by a threshold cut on the leading hadron of each jet candidate. This cut, however, is not safe against collinear splitting of hard partons and thus is systematically explored. The jet spectra are fully corrected for background fluctuations and detector effects utilizing two different unfolding techniques. We compare this measurement to the jet spectrum in p+p collisions and to model predictions, as well as to the results from LHC experiments.

Speaker: Jan Rusnak (Nuclear Physics Institute Prague)

16:30 Inhomogeneous chiral phase in external magnetic field

There have been theoretically and experimentally explored the QCD phase diagram in the density ($\mu$)-temperature ($T$) plane. Usually the phase structure is studied by assuming the spatially and temporally constant order parameter. Recently the possibility of inhomogeneous chiral phase has attracted much interest [1,2] in the light of progress in heavy-ion collisions or observation of compact stars. Theoretically discovering of the Hartree-Fock solutions in 1+1 dimension has also stimulated the studies. The effect of the external magnetic field on the chiral transition or deconfinement has been also studied by the lattice QCD simulation for $\mu=0$ [3]. It should be important, because quark matter is exposed in the strong magnetic field in compact stars or heavy-ion collisions. Theoretically the magnetic field leads to various phenomena in QCD such as chiral magnetic effect, magnetic catalysis or magnetic inhibition of the spontaneous symmetry breaking effect. We study the chiral transition in the presence of the magnetic field by using the NJL model. We focus here on the inhomogeneous chiral phase. For the analysis, the complex order parameter $\Delta := -2G\left[ \left<\overline \psi \psi \right> +i\left<\overline \psi i\gamma^5\tau^3\psi \right>\right]$ is used; dual chiral density wave (DCDW) $\left[ \Delta(x) =me^{iqz} \right]$ and real kink crystal (RKC) $\left[ \Delta(x) =\frac{2m\nu}{1+\sqrt{\nu}}{\rm sn}\left( \frac{2mz}{1+\sqrt{\nu}}, \nu\right) \right]$ have been commonly used as typical configurations. The properties of DCDW has been studied by Frolov et al. in the presence of the magnetic field [4]. They found that DCDW phase develops in a wide density region at $T=0$. They also found some peculiar behavior of the amplitude and the wavevector. However, they did not take into account the possibility of RKC, while RKC has been suggested to be favored in the absence of the magnetic field. Here we introduce the hybrid configuration $ \left[ \Delta(x) = \frac{2m\nu}{1+\sqrt{\nu}}{\rm sn}\left( \frac{2mz}{1+\sqrt{\nu}},\nu \right)e^{iqz} \right] $, which smoothly connects both DCDW and RKC, and demonstrate that the magnetic field favors the phase modulation: it is found through the analysis of the thermodynamic potential that the wavevector $q$ takes a nonzero value in the presence of the magnetic field and DCDW and RKC coexist in the weak magnetic field at moderate densities. In the high magnetic field pure DCDW appears over all density region. It is also shown that there is a first order phase transition between inhomogeneous phases in the presence of magnetic field. Such hybrid phase may appear in compact stars. [1] E.Nakano, T.Tatsumi, Phys.Rev.D 71 (2005) 114006 [2] D.Nickel, Phys.Rev.D 80 (2009) 074025; D.Nickel, Phys.Rev.Lett.103 (2009) 072301 [3] GH.S.Bali, F.Bruckmann, G.Endrodi, Z.Fodor, S.D.Katz, A.Schafer, Phys. Rev.D86 (2012) 071502 [4] I.E.Frolov, V.Ch.Zhukovsky, K.G.Klimenko, Phys. Rev. D82 (2010) 076002

Speaker: Kazuya Nishiyama (Kyoto U.)

16:30 Inhomogeneous phases in 1+1 and 1+3 dimensional effective quark models

Chiral symmetry is a symmetry of the QCD Lagrangian, which is spontaneously broken due to nonperturbative phenomena. As a con- sequence, a chiral condensate, which corresponds to a vacuum’s con- densate of quark-antiquark pairs, emerges. Usually, this condensate is treated as constant over space, but analytic as well as numerical stud- ies show that an inhomogenous condensation is favored at high density. However, in most cases it is not possible to calculate analytically the emergence of inhomogeneous condensation. Therefore it is important to improve numerical methods: in the talk, we present a new numerical approach which is capable to reproduce well-known analytic results in 1+1 as well as in 1+3 dimensions. We also outline which studies can be performed with this method in the near future.

Speaker: Mr Achim Heinz (ITP Frankfurt am Main)

Slides qm2014_poster.pdf

16:30 Initial state fluctuations in pA and AA collisions and their influence on geometry measures

Fluctuations in physics observables and flow effects in heavy-ion collisions have been topics of particularly interest in recent years as they may provide important signals regarding the formation of quark-gluon plasma, the existence of a critical point and the evolution of the system. Moreover, the fluctuations and correlations measured in the final stage have their sources at least partly in the initial fluctuations and the initial-state geometry provided the initial effects are not largely altered by the intermediate evolution of the system. In the framework of the Glauber approach with the use of the GLISSANDO generator we provide predictions for basic initial state characteristics, like the number of target (projectile) participants and its event-by-event fluctuations as well as inelastic and production cross sections, for various p+A and A+A collisions. Such predictions are particularly interesting for those who study signals of the formation of quark-gluon plasma. We also investigate sensitivity of the azimuthal eccentricity parameters and the correlation of directions of the principal axes associated with the Fourier components to the particular variant of the Glauber Monte Carlo like the wounded-nucleon model, the mixed model or the hot-spot model. Moreover we show the role of the nucleus deformation in the geometry measures in relativistic heavy-ion collisions.

Speaker: Dr Grzegorz Stefanek (Jan Kochanowski University (PL))

Slides QM2014_GStefanek_poster.pdf

16:30 Intermediate Silicon Tracker For STAR HFT Upgrade

A Heavy Flavor Tracker (HFT) has been installed in the STAR experiment at the Relativistic Heavy Ion Collider since January 2014. It greatly enhances the capability for heavy flavor studies by measurements of displaced vertices and direct topological reconstruction of open charm hadrons. The HFT consists of two inner layers of silicon pixel detectors, an intermediate layer of silicon pad detector and an outer layer of silicon strip detector. The Intermediate Silicon Tracker (IST) is the third layer made of silicon pad sensors, which have a position resolution of about 180 (1800) microns in the r-$\phi$ (z) direction. In this poster, we will present the design of the IST detector system, and its performance in the cosmic ray tests and ongoing physics data taking with Au-Au collisions.

Speakers: Dr Yaping Wang (University of Illinois at Chicago), Dr Zhenyu Ye (University of Illinois at Chicago)

Poster IST_Poster_QM2014_v2.pdf

16:30 Is the LHC Fireball Less Opaque Than the RHIC Fireball, and Why?

High energy jets, penetrating the hot QCD matter created in heavy ion collisions, provide unique probe of the medium property. Recently there has been a lot of interests in extracting the possibly nontrivial temperature dependence of the jet-medium coupling. Particularly sensitive to such T-dependence are two sets of observables: the anisotropy of jet energy loss via the azimuthal angle dependence of suppression $R_{aa}(\phi)$ (or equivalently the various harmonic coefficients $v_n$ at high $p_t$), as well as the evolution of the overall suppression with beam energy, $R_{aa}(\sqrt{s})$. We report our systematic study of these observables using event-by-event simulations, and compare with available data from RHIC and LHC. The results strongly suggest a nontrivial temperature dependence of the jet-medium coupling and in particular its enhancement near the parton/hadron phase boundary. Recently emerging evidences for such a possibility from various other jet modelings, as well as efforts to understand such peculiar medium property from microscopic theories will also be discussed. Finally we also briefly discuss potentially final state jet attenuation effect in (possibly created) hot medium in the "mini-bang" (pPb and dAu collisions) and demonstrate that jet quenching anisotropy could provide a clean probe to tell whether there is substantial final state interaction in those collisions.  References: Zhang & Liao, arXiv:1311.5463; PRC89(2014)014907; PRC87(2013)044910; PLB713(2012)35.

Speaker: Dr Xilin Zhang (Institute of Nuclear and Particle Physics and Department of Physics and Astronomy, Ohio University, Athens, OH, USA)

16:30 Isolated photon-hadron and $\pi^0$-hadron correlations in pp and Pb-Pb collisions with the ALICE experiment

Correlations between high-$p_{\rm T}$ photons or leading hadrons and charged hadrons are considered as a sensitive probe for studying medium-induced parton energy loss and jet modification in heavy-ion collisions. The prompt photons are produced in association with jets in pp and Pb-Pb collisions. Such processes can be tagged experimentally via photon isolation analysis and the correlation of such photons with hadrons in the opposite side in azimuth. Prompt photons energy is close to the energy of the parton at the origin of the jet in the opposite side and thus the correlation with the hadrons allows a measurement of the jet fragmentation. Neutral mesons production at high $p_{\rm T}$ is also modified in Pb-Pb collisions due to the same parton energy loss mechanism. In addition, the jet fragments in the meson direction, and the opposite jet in azimuth, are also quenched in the medium. Therefore, the charged particles yield associated with the high-$p_{\rm T}$ neutral meson is modified in Pb-Pb collisions compared to the pp reference at the same colliding energy. The ALICE experiment at the LHC performs measurements of the azimuthal correlation between neutral pions or isolated photons triggered by the electromagnetic calorimeter EMCAL, and charged hadrons detected in the central tracker. Results of $\pi^0$-hadron correlations measurements in pp and Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV as well as jet fragmentation tagged by isolated photons in pp collisions at $\sqrt{s}$ = 7 TeV, will be presented.

Speaker: Xiangrong Zhu (Central China Normal University CCNU (CN))

16:30 J/$\psi$ polarization measurement in p+p collisions at $\sqrt{s}$ = 500 GeV in STAR

Experimental data on the J/$\psi$ cross section in $p$+$p$ collisions can be described relatively well by many models that are currently available on the market. These models have different predictions regarding the J/$\psi$ polarization. Therefore measurements of the J/$\psi$ polarization may allow discriminating among the models and provide new insight into on the J/$\psi$ production mechanism. The previous STAR J/$\psi$ polarization analysis was performed only for the polarization parameter $\lambda_{\theta}$ and in one reference frame due to limited statistics. Proton-proton data taken in year 2011 at $\sqrt{s}$ = 500 GeV with integrated luminosity of 22 $pb^{-1}$ will allow us to extract the full information about the dielectron decay angular distribution of the J/$\psi$ in different reference frames (helicity, Collins-Soper and Gottfried-Jackson frames). In this presentation, the status of the J/$\psi$ polarization measurement at mid-rapidity at $\sqrt{s}$ = 500 GeV in $p$+$p$ collisions in the STAR experiment will be shown.

Speaker: Barbara Trzeciak (Czech Technical University in Prague)

Poster QM14poster_JpsiPolarization_v5.pdf

16:30 Jet azimuthal distributions with high $p_{\rm T}$ neutral pion triggers in pp collisions from LHC-ALICE

Jet measurements play an essential role in probing the hot and high energy density matter in heavy-ion collisions through parton energy loss and in observation of possible modification of the hot and dense matter by the deposited energy. In this poster, we report azimuthal distributions of charged jets with respect to high $p_{\rm T}$ neutral pion triggers in pp collisions at $\sqrt{\rm s}$ = 7 TeV from ALICE. For neutral pion identification, an electromagnetic calorimeter (EMCal) is used. Jets are reconstructed from charged particle tracks that are measured by the Time Projection Chamber (TPC) and Inner Tracking System (ITS). The sample of neutral pions is enhanced by using the EMCal gamma trigger in combination with a shower shape analysis to identify neutral pions. We report conditional yields and Gaussian widths of both near- and away-side correlation peaks as function of neutral pion trigger $p_{\rm T}$ and jet $p_{\rm T}$. The results will be also compared with PYTHIA.

Speaker: Daisuke Watanabe (University of Tsukuba (JP))

Slides QM2014_poster_v12.pdf

16:30 Jet quenching effects on the direct, elliptic, and triangular flow at RHIC

In this talk we shall discuss how the energy-momentum deposited by partonic dijets in the quark-gluon plasma may affect the direct, elliptic and triangular flow of low (and intermediate) $p_T$ hadrons in Au+Au collisions at RHIC. The dijets are modeled as external sources in the energy-momentum conservation equations, which are solved on an event-by-event basis within the ideal hydro approximation. Differential anisotropic flow coefficients in the range $p_T > 1$GeV are found to be significantly enhanced if each jet deposits, on average, more than 8 GeV in the medium. Moreover, because this jet-induced extra anisotropic flow is not related to the initial fluctuations of the geometry, the correlation between the integrated $v_2$ and $v_3$ coefficients and their corresponding eccentricities previously found to hold in jetless simulations is considerably weakened. The extra amount of direct flow induced by dijets may be quantified by comparing the azimuthal dependence of dihadron correlations in dijet events with the corresponding quantity computed in events without dijets. This information can be used to give a rough estimate of the magnitude of the effective coupling between the jets and the medium.

Speaker: Rone Andrade (Universidade de São Paulo USP)

16:30 Jet reconstruction and calibration in heavy-ion collisions with the ATLAS detector

Jets produced in heavy-ion collisions are one of the important hard probes that provide information about the hot and dense medium created in heavy ion collisions. The performance of the jet reconstruction is of great importance since it provides basis for each jet measurement. Due to the large underlying background and its fluctuations, the precise jet reconstruction is nontrivial and challenging. Beside the basic jet performance we concentrate namely on the methods used for the calibration of jet energy. The so-called numerical inversion used to calibrate jets in the ATLAS experiment is introduced and discussed.

Speaker: Tomas Kosek (Charles University (CZ))

Slides tkosek_poster_QuarkMatter2014.pdf

16:30 Jet shapes and fragmentation functions in pp and PbPb collisions with CMS

The fragmentation function and transverse momentum profile (shape) of inclusive jets in 2.76 TeV PbPb collisions are reported in this poster. Jets with transverse momentum $p_T$ > 100 GeV/c are measured using anti-$k_T$ algorithm with radius dR=0.3. Charged particles with p$_T$ > 1 GeV/c are used to investigate the fragmentation pattern. The pp collisions at the same center-of-mass energy is analyzed to be used as a reference for the observation of medium effects in PbPb collision. A centrality-dependent modification of the fragmentation function and jet shape is found. A significant enhancement of charged particles of $p_T$ < 3GeV/c and their rearrangement toward periphery of jet cone are observed from the PbPb/pp ratio for the most central collisions.

Speaker: Yongsun Kim (Korea University (KR))

Slides QM2014_QuarkMatter_Yongsun_poster_v5.pdf

16:30 Jet-medium excitation and gamma-jet asymmetry

Medium modification of γ-tagged jets and dijets in high-energy heavy-ion collisions is investigated within a Linearized Boltzmann Transport model for jet propagation that includes both elastic parton scattering and induced gluon emission. Inclusion of recoiled medium partons in the reconstruction of partonic jets is found to significantly reduce the net jet energy loss. Experimental data on γ-jet asymmetry and survival rate in Pb + Pb collisions at √{s}=2.76 TeV can be reproduced. Medium modifications of reconstructed jet fragmentation function, transverse profile and energy flow outside the jet-cone are found to be sizable especially for γ-tagged jets with small values of x=pTjet/pTγ. Medium modification factor of γ-tagged jet and dijets correlation, especially dijets momentum imbalance are also studied.

Speaker: Yan Zhu (University of Santiago de Compostela)

Poster Qm2014.pdf

16:30 Kaon femtoscopy in Pb-Pb collisions with ALICE at the LHC

Identical kaon femtoscopic correlations allow one to measure the space-time characteristics of particle production using the combination of quantum statistics and final state interactions. Kaon femtoscopy provides an excellent complement to pion analyses as it extends the range over which we can study the momentum dependence of the femtoscopic radii and allows us to look for a transverse mass scaling predicted by hydrodynamical models. Neutral and charged kaon analyses require different experimental procedures and thus provide a good consistency check. We present the results of identical kaon femtoscopy in Pb-Pb collisions at the LHC with ALICE. One-dimensional femtoscopic radii ($R_{\rm inv}$) and lambda parameters from neutral and charged kaons are shown for several ranges of transverse pair momentum ($k_{\rm T}$) and centrality. The results are compared to other femtoscopic analyses as well as theoretical model predictions. Also, for the first time, 3D correlation functions and extracted fit parameters from neutral kaons are shown.

Speaker: Matthew Donald Steinpreis (Ohio State University (US))

Poster https://drive.google.com/file/d/0By3nEPDhwH4jN2o2bGNtV0JScnM/preview

16:30 Knee structure in the elliptic flow in ultracentral U+U collisions

Using event-by-event viscous fluid dynamics to evolve fluctuating initial density profiles for U+U collisions, we find a "knee"-like structure in the elliptic flow as a function of collision centrality, located around 0.5% centrality as measured by the final charged multiplicity. This knee is due to the preferential selection of tip-on-tip collision geometries by a high-multiplicity trigger. It arises from a similar knee in the ellipticity distribution in the initial states; hydrodynamic evolution translates the knee in the ellipticity vs. centrality into a knee of the elliptic flow in the final state. The conversion efficiency v2/ε2 is found to be independent of centrality in the knee region. A non-monotonic centrality dependence of v2/ε2 as initially reported by the STAR collaboration can be obtained by normalizing the final v2 values with initial eccentricities calculated from a different initial-state model than the one used in the hydrodynamic simulations. – No knee structure is seen in odd flow harmonics. A weaker knee structure in the centrality dependence of the 4th-order eccentricity is washed out by nonlinear hydrodynamic evolution effects and thus no longer visible in the centrality dependence of the final quadrangular flow v4. – We find that the knee structure in v2 is robust against adding Γ-distributed multiplicity fluctuations, consistent with constraints from measured multiplicity distributions in p+p collisions, but may be washed out when allowing for extreme hot spots as implemented by Rybczynski et al. [Phys. Rev. C 87 (2013) 044908]. – A deeper analysis of these structures is facilitated by imposing additionally a tight cut on complete nuclear overlap by using the Zero Degree Calorimeters (ZDCs). We show results exploring the power of such cuts in selecting specific collision geometries and their impact on anisotropic collective flow.

Speaker: Andy Goldschmidt (The Ohio State University)

Poster goldschmidtANDY_poster.pdf

16:30 Lambda Polarization in peripheral heavy ion collisions

Due to the low viscosity and strongly interacting QGP at high LHC energies flow fluctuations were observed up to the 8th flow harmonics. Similarly rotation, turbulence and even Kelvin-Helmholtz Instability were predicted and these may be observable by different methods. Apart of the usual flow harmonics analysis, other methods like two particle correlations, or particle polarizations may arise as a consequence of these processes. The appearance of turbulent phenomena in these experiments would be additional direct proof of the low viscosity. In particular we observed in 3+1D fluid dynamical calculations at LHC and RHIC energies that Lambda polarization arising from thermal and mechanical equilibrium, can provide measurable signal in given azimuthal directions. The signal is predicted to be somewhat stronger at RHIC energies because the higher temperature at LHC decreases thermal vorticity (polarization) even if the angular momentum is larger at LHC. This mechanism is considerably stronger than the polarization arising from the direct electro-magnetic effect of the strong and rapidly changing fields during the collision. The talk is based on recent results and the following publications: L.P. Csernai, V.K. Magas, H. Stoecker, and D.D. Strottman, Phys. Rev. C 84, 024914 (2011). L.P.Csernai, D.D.Strottman, C.Anderlik, Phys.Rev.C 85, 054901 (2012). L.P. Csernai, V.K. Magas, D.J. Wang, Phys. Rev. C 87, 034906 (2013). F. Becattini, L.P. Csernai, D.J. Wang, Phys.Rev. C 88, 034905 (2013).

Speaker: Laszlo Csernai (Department of Physics and Technology)

Poster Magas-poster-QM2014.pdf Poster-QM-Cs-B-W-Polar.pdf

16:30 Lattice QCD study on quark mass dependence of quarkonium properties at finite temperature

As a consequence of the melting of quarkonia due to the color Debye screening in a hot medium, suppression of quarkonium yields is expected to be observed in the quark gluon plasma produced in relativistic heavy ion collision experiments at RHIC and LHC. In fact, suppression of the $J/\Psi$ yield has already been observed both at RHIC and LHC and thus theoretical understanding of charmonium properties at high temperature is important to explain experimental results. Moreover, recently, sequential $\Upsilon$ suppression at LHC has been reported by the CMS collaboration [1], which inspires theoretical interest of in-medium bottomonium behavior. In this talk we report our lattice QCD study on quarkonium properties at finite temperature, which extends our previous study [2] with a couple of lattice spacings toward the continuum limit. Similarly to a previous charmonium study [3], we perform numerical simulations on large and fine isotropic lattices by using quenched gauge field configurations. To investigate differences between charmonium and bottomonium states, we vary the quark masses in the range between the charm and bottom masses. Spatial and temporal meson correlation functions are computed at temperatures in a range from 0.8$T_c$ to 1.6$T_c$ at both vanishing and finite momenta. We will discuss the temperature and quark mass dependence of the screening masses and the change and dissociation of various quarkonium states in the QGP. The spectral properties obtained in this study also provide information on a transport coefficient, the heavy quark diffusion coefficient, and its temperature and mass dependence. [1]S. Chatrchyan *et al.* [CMS Collaboration], Phys. Rev. Lett. **109**, 222301 (2012) [arXiv:1208.2826 [nucl-ex]]. [2]H. Ohno, arXiv:1311.4565 [hep-lat]. [3]H.-T. Ding, A. Francis, O. Kaczmarek, F. Karsch, H. Satz and W. Soeldner, Phys. Rev. D **86**, 014509 (2012) [arXiv:1204.4945 [hep-lat]].

Speaker: Hiroshi Ono (University of Tsukuba)

Poster qm2014_poster_ohno_ver2.pdf

16:30 Light vector meson production in p-Pb and Pb-Pb collisions measured with the ALICE detector

Light vector meson ($\rho$, $\omega$, $\phi$) production provides key information on the hot and dense state of strongly interacting matter produced in high-energy heavy-ion collisions. In particular, strangeness production can be accessed through the measurement of the $\phi$ meson, while the measurement of the $\rho$ spectral function can be used to reveal in-medium modifications of hadron properties close to the QCD phase boundary. The detection of vector mesons through their decay in dileptons has the advantage, with respect to hadronic decays, that the decay products are not influenced by final state interactions. The ALICE experiment at the LHC can access vector mesons produced at forward rapidity through their decays in muon pairs. We present results on vector meson production in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. In p-Pb collisions, measurements of the $\phi$ yield and the nuclear modification factor in the rapidity ranges $2.03 < y < 3.53$ and $-4.46 < y < -2.96$ are shown. An asymmetry between the yields at forward and backward rapidity is observed. Data are compared to the predictions provided by commonly used event generators. In Pb-Pb collisions, the $\phi$ yield and the nuclear modification factor are obtained as a function of centrality in the intermediate $p_{\rm T}$ region ($2 < p_{\rm T} < 5$ GeV/$c$) and for $2.5 < y < 4$. Dimuon data at forward rapidity are compared to the measurement in the KK channel at mid rapidity and to theoretical predictions based on hydrodynamic calculations.

Speaker: Alessandro De Falco (Universita e INFN (IT))

Poster 2014-May-16-conferencefile-adf_qm14.pdf

16:30 Local equilibration and negative contributions: Investigating the transition interfaces in hybrid approaches

Hybrid approaches are very successful in describing the dynamics of heavy ions collisions. The hot and dense medium is described well by fluid dynamic calculations whereas hadron transport accounts for particle rescatterings in the late stages of the reaction. The application of fluid dynamics requires rapid thermalization of the system. How and whether it is reached remains debatable. In this contribution we use the UrQMD hadron transport to study the early time dynamics of heavy ion collisions at $\sqrt{S_{NN}} = 3-20$ GeV. We consider the energy-momentum tensor of coarse-grained UrQMD events as a function of space and time to explore the degree of local equilibration of the system. In addition, to find out how well fluid dynamics can describe the system at these energies, we initialize UrQMD and viscous hydrodynamics in the same way and compare their $T^{\mu \nu}$ during the space-time evolution. At the end of the fluid-dynamical evolution particles are generated on the transition hypersurface according to the Cooper-Frye formula. This description suffers from so-called negative contributions – particles flying from outside back to the fluid-dynamical region. We compare negative contributions obtained in the Cooper-Frye description to the actual particle trajectories across the hypersurface, again in a coarse-grained UrQMD evolution, where all the microscopic information is available. We show that results of these two calculations may significantly differ and the discrepancy becomes especially large, when the transition surface is not smooth, which may be the case in event-by-event calculations.

Speaker: Dmytro Oliinychenko (Frankfurt Institute for Advanced Studies, Germany; Bogolyubov Institute for Theoretical Physics. Kiev, Ukraine)

Poster QM14_poster_Oliinychenko.pdf

16:30 Long-range two-particle correlations with K0s and Lambda in pPb and PbPb collisions in CMS

Measurements of two-particle correlations with identified K^0_s and Lambda trigger particles in 5.02 TeV pPb and 2.76 TeV PbPb collisions are presented. One unique feature of this analysis is the implementation of a high-multiplicity trigger during the 2013 LHC pPb run, which enables the correlation studies to be performed up to a multiplicity range that is comparable to mid-central PbPb collisions at 2.76 TeV. Performance of the K^0_s and Lambdas reconstruction at CMS is presented. The second-order (v_2) and third-order (v_3) anisotropy harmonics of K^0_s and Lambda are extracted from long-range correlations as a function of particle multiplicity and pT. The wide pT coverage and rich sample of high multiplicity pPb events allow: (1) a precise examination of the mass ordering effect of v_n at low pT as predicted by hydrodynamics for a collectively expanding medium; (2) exploration of possible constituent quark number scaling of v_2 and v_3 between mesons and baryons as was observed in high-energy nucleus-nucleus collisions.

Speaker: Zhenyu Chen (Rice University (US))

Slides QM2014_PIDFlow_poster_Zhenyu_v6.pdf

16:30 Low $p_{T}$ non-photonic electron production in AuAu collisions at $\sqrt{s_{\rm NN}} = $ 200 GeV

Particles containing heavy quarks are very useful tool to investigate the properties of hot and dense matter produced in early stage of the relativistic heavy ion collision in terms of the mechanisms of their interaction with nuclear matter. This can be studied by non-photonic electrons (NPE) coming from semi-leptonic decays of heavy flavor hadrons. In year 2010, STAR has collected a large sample of minimum bias Au+Au events at $\sqrt{s_{\rm NN}} = $ 200 GeV with newly implemented full barrel Time-Of-Flight detector. This enables us to analyze NPE production in the low $p_{T}$ region (0.2 < $p_{T}$ < 2.0 GeV/c) with high statistics. In this presentation we report on status of the low $p_{T}$ NPE analysis in Au+Au collisions at $\sqrt{s_{\rm NN}} = $ 200 GeV at STAR.

Speaker: Kunsu Oh (Pusan National University (KR))

Poster QM14posterVfinal.pdf

16:30 Low Mass Vector Meson Production in d+Au collisions at $\sqrt{s}_{NN}$ = 200 GeV with the PHENIX Detector at RHIC

Low mass vector meson ($\omega$, $\rho$, and $\phi$) production in high-energy heavy-ion collisions provides key information on the hot and dense state of the strongly interacting matter produced in such collisions. They are sensitive to the medium-induced effects such as strangeness enhancement, modification of the resonance line shapes and their relative production rates in leptonic and hadronic decay modes linked to the chiral symmetry restoration. Measurements in the dilepton channels are especially interesting since leptons interact only electromagnetically, thus carrying the information from their production phase directly to the detector. Results on light vector meson production in p+p collisions serve as a reference for heavier collision systems. Measurements in d+Au are used to quantify the cold nuclear matter effects which are critical to interpreting the heavy ion results. The PHENIX detector provides the capabilities to measure the light vector meson production in a wide range of transverse momentum and rapidity to study various cold nuclear effects such as soft multiple parton rescattering and modification of the parton distribution functions in nuclei. The PHENIX collaboration at RHIC collected $\sim60 nb^{-1}$ in d+Au collisions at $\sqrt{s}_{NN}$ = 200 GeV. In this poster we report recent PHENIX results for ($\omega + \rho$) and $\phi$ mesons invariant production spectra and nuclear modification factors from this data.

Speaker: Dr Murad Sarsour (Georgia State University)

16:30 Low Mass Vector Mesons Production in $p+p$ collisions at forward rapidity in the dimuon channel at $\sqrt{s}$ = 200 and 510 GeV at RHIC

Low mass vector mesons ($\rho$, $\omega$, $\phi$) provide important information on the hot and dense state of strongly interacting matter produced in heavy ion collisions. Among them, strangeness enhancement, a phenomenon associated with soft particles in the bulk matter, can be accessed through the measurement of the ratio $\phi$/($\rho+\omega$). Low mass vector meson production in $p+p$ collisions provides a reference for this study. In addition, vector meson production in $p+p$ collisions is an important tool to study QCD, providing data to tune soft phenomenological QCD models and to compare to hard pQCD calculations. The PHENIX experiment at RHIC is capable of studying low-mass vector meson production with two muon spectrometers covering the rapidity range $1.2 < |y| < 2.2$, offering a complementary measurement to the one done at mid-rapidity. In this poster we report recent PHENIX results on the measurement of differential cross sections, $p_T$ and rapidity dependencies of $(\rho+\omega)$ and $\phi$ mesons production in $p+p$ collisions at $\sqrt{s}$=200 GeV based on the data sample collected in 2009. Since 2012, the forward vertex detector (FVTX) offers an improved dimuon invariant mass resolution. Latest status of the light vector meson measurements using the data collected in 2013 with FVTX at $\sqrt{s}$=510 GeV will be presented.

Speaker: Dr Raphael Tieulent (Universite Claude Bernard-Lyon I (FR))

Poster Tieulent_QM2014_PHENIX_LMR_pp_Poster.pdf

16:30 Low-$p_{\rm T}$ J/$\psi$ in Pb-Pb collisions at forward rapidity with ALICE at the LHC

The aim of ultra-relativistic heavy-ion collisions is the study of nuclear matter at high temperature and pressure where quantum chromodynamics predicts the existence of a deconfined state of nuclear matter, the Quark-Gluon Plasma (QGP). Heavy quarks are expected to be produced in the initial partonic scatterings and interact with the deconfined medium making them ideal probes of the QGP. According to the color-screening model, quarkonium states are suppressed in the medium with different dissociation probabilities for the various states. Recent results from the ALICE collaboration on the measurement of the nuclear modification factor and elliptic flow of inclusive J/$\psi$ indicate that a significant fraction of the observed J/$\psi$ is produced via the recombination of charm quarks from the QGP phase. Quarkonium detection at forward rapidity is performed with the ALICE muon spectrometer in the range -4 $< \eta <$ -2.5 down to $p_{\rm T}$ = 0. We report on the first measurement of a low-$p_{\rm T}$ J/$\psi$ yield excess ($p_{\rm T} <$ 300 MeV/$c$) in Pb-Pb collisions at the LHC, in the centrality bins 50-70$\%$ and 70-90$\%$. Photoproduction of J/$\psi$ (occuring at $b < 2R$) is proposed as the underlying physics mechanism. Such a mechanism may represent a promising signature to probe the charmonium color-screening dissociation in the QGP at LHC energies. In this poster, we will present two methods to quantify the J/$\psi$ low-$p_{\rm T}$ yield excess and we will give the status and perspectives of this analysis.

Speaker: Laure Marie Massacrier (Laboratoire de Physique Subatomique et des Technologies Associe)

Poster posterQM_save_v2.pdf

16:30 Low-mass di-electron reconstruction at the CBM experiment

The Compressed Baryonic Matter (CBM) experiment is designed to investigate high baryon density matter at moderate temperatures in Au+Au collisions at 4-35A GeV beam energies. Among the different observables, lepton pairs are particularly attractive, as they directly probe the entire space-time evolution of the expanding fireball formed in such collisions, escaping freely without final-state interaction. This includes detailed investigations of low-mass vector mesons in their di-electron decay channel. In the simulation studies we investigate the feasibility to effectively reduce the combinatorial background with the currently foreseen experimental setup, which does not provide electron identification in front of the magnetic field. The strategy of electron identification and background suppression will be discussed. Simulation results with most-up-to date realistic detector response as well as detailed background studies will be presented.

Speaker: Elena Lebedeva

Poster QM2014_Lebedeva.pdf

16:30 Mach cones in viscous heavy-ion collisions

The formation of Mach cones is studied in a full $(3+1)$-dimensional setup of ultrarelativistic heavy-ion collisions, considering a transverse and longitudinal expanding medium at RHIC energies. For smooth initial conditions and central collisions the jet-medium interaction is investigated using high-energy jets and various values of the shear viscosity over entropy density ratio, $\eta/s$. For small viscosities, the formation of Mach cones is proven, while for larger viscosities the characteristic structures smear out and vanish eventually. The formation of a double-peak structure both in a single and a multiple jet event is discussed.

Speaker: Ioannis Bouras (University of Frankfurt a.M.)

16:30 Mapping the Little Bangs Through Energy Density and Temperature Fluctuations

Heavy-ion collisions at relativistic energies, which are accessible at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), are often referred to as little bangs. Experiments at these energies probe the conditions which prevail at freeze-out, and often it is not possible to define the correct equation-of-state (EoS) and the conditions at the initial stages of the collision. By employing hydrodynamic evolution of the fireball [1] created in the collisions, we have generated maps of the energy density ($\epsilon$) and temperature ($T$) of the system throughout its evolution. With the help of the maps, we obtain time evolution of the fluctuations in $\epsilon$ and $T$. We have shown for the first time that the method of interpolation of fluctuations obtained from the maps can provide a powerful technique in looking back at the initial stages of the heavy-ion collisions. In case of cosmic microwave background radiation (CMBR), temperature maps of the sky [2], made by scanning in $\theta$-$\phi$ bins, provide vital information regarding the age and composition of the Universe, galaxy formation, expansion rate, etc. This is possible by analyzing the map to extract temperature fluctuations and making power spectrum. For heavy-ion collisions, we propose to make temperature maps in rapidity and azimuthal angle ($y$-$\phi$). This is demonstrated by using the AMPT event generator. By making correspondence with the evolution of fluctuations from hydrodynamics, vital information regarding the fireball can be obtained at very early stage and throughout the evolution of the system [3]. We will present this new method, first results and make the proposal for its application to experimental data at RHIC and LHC. [1] H. Holopainen, H. Niemiand and K.J. Eskola, Phys. Rev.C 83, 034901(2011). [2] C. L. Bennett et al. [WMAP Collaboration], Astrophys. J. Suppl. 148, 1 (2003); E. Komatsu et al. [WMAP Collaboration], arXiv:0803.0547 [astro-ph]. [3] S. Basu, R. Chatterjee, B.K. Nandi and T.K. Nayak (in preparation).

Speaker: Sumit Basu (Department of Atomic Energy (IN))

Poster Maps_Little_Bang_Poster.pdf

16:30 Master equations of quarkonia in the Lindblad form

Understanding the quantum dynamics of quarkonia is essential in the description of bottomonia and charmonia in the quark-gluon plasma. So far, it has been quite naively assumed that their dynamics can be described by the Schrödinger equation with in-medium, screened potential. Such a naïve approach is not correct anymore, in particular if one wants to study their time-evolution. After the discovery of imaginary part in the in-medium potential [1], it must be recognized that quarkoia should be viewed as open quantum systems in the environment of quark-gluon plasma [2]. In the open quantum system, master equation instead of the Schrödinger equation describes the quantum dynamics of quarkonia. Open quantum system techniques, such as influence functional approach, have been applied to quarkonia [3]. In this presentation, I will summarize developments in this approach and show an additional step toward a more complete description. In particular, I will show how to obtain the Lindblad-form master equation, which preserves the complete positivity of the density matrix of the system [4]. ---------- References: [1] M. Laine et al., JHEP 0703 (2007) 054; JHEP 0705, 028(2007); A. Beraudo, J. P. Blaizot and C. Ratti, Nucl. Phys. A806, 312 (2008); N. Brambilla, J. Ghiglieri, A. Vairo and P. Petreczky, Phys. Rev. D 78, 014017 (2008); A. Rothkopf, T. Hatsuda and S. Sasaki, Phys.Rev.Lett. 108 (2012) 162001. [2] Y. Akamatsu and A. Rothkopf, Phys.Rev. D85 (2012) 105011. [3] Y. Akamatsu, Phys.Rev. D87 (2013) 045016. [4] Y. Akamatsu, in preparation.

Speaker: Yukinao Akamatsu (Nagoya University)

Slides Quark_Matter_2014.pdf

16:30 Measurement of $\phi$ meson nuclear modification factors in p-Pb and Pb-Pb collisions in the ALICE experiment at the LHC

Measurements of hadron spectra in proton-proton and nucleus-nucleus collisions at the LHC provide the means to study the mechanisms of particle production and properties of the medium formed in relativistic heavy ion collisions. The $\phi$ meson is a very rich probe since it is sensitive to several aspects of the collision such as strangeness enhancement, chiral symmetry restoration and parton energy loss. Due to its small inelastic cross section the $\phi$ meson is not strongly affected by the late hadronic rescattering and is sensitive to the initial evolution of the system. With a mass similar to that of the proton, it is interesting to see how the $\phi$ meson fits within the meson/baryon pattern of observables. Being a pure s-$\overline{s}$ state, it further constrains the energy loss and recombination pictures. The ALICE Collaboration performed systematic measurement of the $\phi\rightarrow {\rm K}^{+}{\rm K}^{-}$ meson production at mid-rapidity in pp, p-Pb and Pb-Pb collisions at LHC energies. This poster presents recent results on $\phi$ meson invariant yields and nuclear modification factors measured in a wide range of transverse momentum up to 21 GeV/$c$ in pp and p-Pb, Pb-Pb collisions at different centralities.

Speaker: Mikhail Malaev (B.P. Konstantinov Petersburg Nuclear Physics Institute - PNPI ()

16:30 Measurement of $\rm D^0$ azimuthal anisotropy in Pb-Pb collisions with the ALICE detector at the LHC

The ALICE experiment at the LHC studies ultra-relativistic Pb-Pb collisions with the aim of investigating the properties of the high-density state of strongly-interacting matter, expected to be produced in heavy-ion collisions. Heavy quarks are sensitive probes of the medium properties, since they are formed on a shorter time scale with respect to the medium. The elliptic flow ($v_{2}$) of low $p_{\rm T}$ D mesons can bring insight into the degree of thermalization of charm quarks within the medium. The suppression of the yield of high-$p_{\rm T}$ D mesons, measured in different intervals of azimuthal angles relative to the reaction plane, can give access to the path-length dependence of parton energy loss. ${\rm D}^0 \rightarrow {\rm K}^- \pi^+$ decays have been reconstructed in the central rapidity region in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV, using data recorded during the year 2011. The final results on the $\rm D^0$ meson azimuthal anisotropy in Pb-Pb collisions, for different centrality classes, will be presented and the comparison with theoretical models will be described.

Speaker: Davide Caffarri (CERN)

Slides DCaffarri_Dmes_v2_QM2014.pdf

16:30 Measurement of $\rm D^{+}$-meson production in Pb-Pb collisions with the ALICE detector at the LHC

Heavy quarks (charm and beauty) are effective probes to investigate the properties of hot and dense QCD matter created in heavy-ion collisions as they are produced in partonic scattering processes occuring in the early stages of the collision. Due to their long life time, they probe all the stages of the medium evolution and they interact with it losing energy via gluon radiation and elastic collisions with in-medium constituents. The measurement of the nuclear modification factor of the D-mesons provides a key test of parton energy-loss models. These models predict that beauty quarks lose less energy than charm quarks and the latter experience less in-medium energy loss than light quarks and gluons. D-meson ($\rm D^{0}$, $\rm D^{+}$, $\rm D^{*+}$ and $\rm D_{s}^{+}$) production has been measured with ALICE in pp, Pb-Pb and p-Pb collisions at different energies. In particular, we will present the measurement of the $\rm D^{+}$ production in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV performed with the ALICE detector at central rapidity through the exclusive reconstruction of the hadronic decay channel $\rm D^{+} \rightarrow K^{-}$ $\pi ^{+} \pi^{+}$. The results of the measurement of the nuclear modification factor of $\rm D^{+}$ as a function of transverse momentum and centrality will also be presented.

Speaker: Dr Renu Bala (University of Jammu (IN))

Poster rbala_QMPoster.pdf

16:30 Measurement of anisotropic flow of electrons from the decay of heavy-flavour hadrons in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV with ALICE at the LHC

In high-energy heavy-ion collisions, heavy quarks, i.e. charm and beauty, are mainly produced in hard scattering processes in the early stages of the collisions. Therefore they allow one to probe the properties of the deconfined state of strongly-interacting matter formed in such collisions, the Quark-Gluon Plasma (QGP). A parton going through the hot and dense medium can lose energy via both elastic and inelastic collisions with the medium constituents. Heavy-quarks, because of their large masses, are expected to lose less energy than light quarks and gluons, providing a unique test of parton energy loss models. In this contribution, results of the elliptic flow $v_{2}$ of electrons from the semi-leptonic decays of heavy-flavour hadrons measured with ALICE in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV are presented for different centralities. The elliptic flow is the second Fourier coefficient of the azimuthal distribution of particle momenta in the transverse plane with respect to the azimuthal angle of the reaction plane. At low $p_{\rm{T}}$, the $v_{2}$ of the electrons from heavy-flavour hadron decays is sensitive to the degree of thermalization of charm and beauty quarks in the deconfined medium. At higher $p_{\rm{T}}$, the measurement of $v_{2}$ carries information on the path length dependence of in-medium parton energy loss. Electrons are reconstructed in the central rapidity region using different identification strategies in different $p_{\rm{T}}$ regions. The $v_{2}$ of the heavy-flavour decay electrons is extracted subtracting from the measured inclusive electrons $v_{2}$ the contribution of the main background sources. Different approaches are used to subtract the background contributions. The analysis was carried out with various methods that have different sensitivity to non-flow contributions, namely the event plane, scalar product and second order Q-Cumulant methods. Comparisons with measurements at lower collision energy at RHIC and with theoretical models will be presented as well.

Speaker: Andrea Dubla (University of Utrecht (NL))

Poster 2014-May-16-conferencefile-QMPosterADubla_v5(1).pdf

16:30 Measurement of electrons from beauty-hadron decays in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the LHC

Heavy-flavour hadrons, containing charm or beauty quarks, are expected to be probes providing constraints on partonic energy-loss mechanisms in the medium produced in heavy-ion collisions since they are produced at an early stage in the initial hard scattering processes. In particular, the medium-induced parton energy loss is expected to depend on the parton mass and colour charge. This results in a reduction of beauty-quark energy loss compared to charm-quark energy loss. Therefore the separate study of charm and beauty production allows us to test theoretical predictions. Measurements of medium modifications of heavy-flavour transverse momentum distributions in p-Pb collisions allow us to quantify cold nuclear matter effects in the initial state and to deduce the role of final-state effects in Pb-Pb collisions. With the ALICE central barrel detectors, electrons can be identified with high purity down to low transverse momentum. The production of electrons from beauty-hadron decays can be measured using their displacement from the primary vertex thanks to the long lifetime of the beauty hadrons. The status of the analysis of the electrons from beauty decays in p-Pb collisions will be presented.

Speaker: Min Jung Kweon (Inha University (KR))

Poster QM2014_pPb_b2e_final.pdf

16:30 Measurement of electrons from charm and beauty-hadron decays in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the LHC

The characterisation of the Quark-Gluon Plasma (QGP), the deconfined state of strongly-interacting matter produced in high-energy heavy-ion collisions, is the main purpose of ALICE at the LHC. Because of their large masses, charm and beauty quarks are mostly produced in initial hard partonic interactions and thus can be used to probe the medium created in such collisions. The $p_{\rm T}$ differential heavy-flavour yield is an observable sensitive to the energy loss of heavy quarks in the hot and dense medium. In addition to the QGP, the presence of cold nuclear matter in the initial state may affect the production of heavy-flavour hadrons. To quantify these effects and confirm the role of final-state effects in Pb-Pb collisions, a reference measurement in p-Pb collisions is necessary. Electrons from semileptonic decays of heavy-flavour hadrons can be used to measure charm and beauty quark production. The measurement of heavy-flavour decay electrons at mid-rapidity in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE will be presented. The performance of the electron identification using the Time Projection Chamber (TPC) and the Time-of-Flight (TOF) detector of the ALICE central barrel will be demonstrated. After subtraction of the background electrons, the nuclear modification factor $R_{\rm pPb}$ of heavy-flavour decay electrons will be shown and discussed in the context of theoretical predictions including the effects due to the nuclear modification of the parton distribution functions.

Speaker: Jan Wagner (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

Poster 2014-May-18-conferencefile-jwagnerQM14_v5.pdf

16:30 Measurement of exclusive Upsilon photoproduction in pp and pPb collisions at CMS

Results on exclusive photoproduction of $\Upsilon$ states in ultra-peripheral collisions (UPC) of protons and ions at CMS are presented, which provides a clean probe of the gluon distribution at small values of parton fractional momenta $x~10^{-4}-10^{-3}$. The three $\Upsilon$ states (1S, 2S, 3S) are measured in the dimuon decay channel, on top of the photon-photon $ \rightarrow$ $\mu\mu$ QED continuum, in pPb collisions at $\sqrt{s_{NN}}=5.02$~TeV (for integrated luminosity of $L_{int} = 35$ nb$^{-1}$) and in pp at $\sqrt{s}=7$ TeV ($L_{int} = 5.24$ fb$^{-1}$). The total $\Upsilon$ photoproduction cross sections as well as the t-differential distributions are compared to various theoretical predictions. The impact of these data on the central values and uncertainties of the low-x gluon distribution will be assessed.

Speaker: Ruchi Chudasama (Bhabha Atomic Research Centre (IN))

16:30 Measurement of heavy-flavour decay electrons in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE ElectroMagnetic Calorimeter at the LHC

The Quark-Gluon Plasma (QGP) is a high-density state of strongly-interacting matter in which partons are deconfined. This state of matter can be studied experimentally via heavy-ion collisions where the critical temperature and density for the phase transition to the QGP can be attained. Measurements of heavy-flavour (charm and beauty) production in these collisions are of particular interest. Heavy quarks are indeed produced in the early stages of the collision and experience therefore the whole evolution of the system. The ALICE collaboration has measured electrons from heavy-flavour hadron decays in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV at mid-rapidity. A strong suppression of the yield of heavy-flavour decay electrons at high $p_{\rm T}$ is observed in $0-10\%$ most central collisions. Measurements of heavy-flavour production in p-Pb collisions are crucial to understand cold nuclear matter effects on the production in heavy-ion collisions. The production of electrons from heavy-flavor hadron decays has been measured with ALICE in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. Electrons have been identified with the Time Projection Chamber and the Electromagnetic Calorimeter (EMCal). In addition, the EMCal provided a trigger during the p-Pb run of the LHC. The trigger enhances the recorded sample of rare probes, such as high $p_{\rm{T}}$ photons and electrons. The trigger will allow us to extend the $p_{\rm{T}}$ reach for heavy-flavour decay electron measurements. We will show results from the heavy-flavour decay electron measurement using the EMCal.

Speaker: Cristiane Jahnke (Universidade de Sao Paulo (BR))

Slides 2014-May-16-conferencefile-poster_QM2014_Cris_Jahnke_aliceinfo7(1).pdf

16:30 Measurement of higher harmonic flow of $\phi$ meson in STAR at RHIC

One of the main goal of the STAR experiment at Relativistic Heavy Ion Collider (RHIC) is to study the properties of hot and dense matter created in the collision of two heavy nuclei [1]. The higher harmonics of azimuthal anisotropy $v_{n}$ of produced particles are believed to be a sensitive way to characterize the system created in the heavy-ion collision [2,3]. Moreover higher harmonics of $\phi$ meson will be the clean probe for the early dynamics since $\phi$ meson freeze-out early and it has small hadronic interaction cross section. The relation between various $v_{n}$ is sensitive to thermalization and dissipation effects in heavy-ion collision [4]. In this presentation we will present the first measurements of $\phi$-meson $v_{3}(p_{T})$ and $v_{4}(p_{T})$ at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Centrality dependence of $v_{3}(p_{T})$ and $v_{4}(p_{T})$ will be shown and compared to corresponding $v_{2}$ values. Ratios between various harmonics will be presented and possible implication of those results will be discussed. References [1] J. Adams ${\it et al.}$(STAR Collaboration), Nucl. Phys. $\textbf{A 757}$, 102 (2005). [2] L. W. Chen ${\it et al.}$ Phys. Rev. $\textbf{C 69}$, 031901 (2004). [3] L. Adamczyk ${\it et al.}$ (STAR Collaboration),Phys. Rev. $\textbf{C 88}$, 014904 (2013). [4] C. Lang ${\it et al}$. arXiv:1312.7763 [nucl-th] (2013).

Speaker: Anju Bhasin (University of Jammu (IN))

Poster QM_Mukesh_poster_updated_v2.pdf

16:30 Measurement of integrated yields of light flavour hadrons, resonances and (hyper-)nuclei at LHC energies with the ALICE experiment and their description with thermal models

After the successful completion of the first LHC run, a complete dataset of light flavor particles in three collision systems (pp, p-Pb, Pb-Pb) is available for detailed comparisons with thermal model descriptions. These models have been successful in describing particle production in heavy-ion collisions at RHIC and SPS energies. The evolution of particle yields and ratios from RHIC to LHC energies will be discussed. We will present recent fits to the ALICE data and compare the achievable precision in describing different collision systems at different centralities, event multiplicities and center of mass energies. The experimental significance of deviations between data and model will be discussed in detail as well as differences between equilibrium and non-equilibrium thermal models.

Speaker: Roberto Preghenella (Universita e INFN (IT))

Poster QM2014_thermalposter.pdf

16:30 Measurement of J/$\psi$ yields at midrapidity in 200 GeV $Au+Au$ collisions with PHENIX

For many years it has been expected that the suppression of J/$\psi$ production in heavy ion collisions can provide some insight into conditions inside the deconfined Quark Gluon Plasma (QGP). A measurement of J/$\psi$ di-electron decays at midrapidity is particularly desirable for providing insight on quarkonium formation in the plasma since cold nuclear matter effects are smaller there than at forward and backward rapidity. The 2010 RHIC run has five times the luminosity of the last the data set used for a dielectron measurement at midrapidity. The Hadron Blind Detector (HBD) was added to PHENIX for operation in 2010 to study low mass dielectron pairs, with the goal of improving electron identification by eliminating conversion electrons from the beam pipe, and hadrons misidentified in the Ring Imaging Cherenkov and the Electromagnetic Calorimeter. The presence of the HBD can also be beneficial for the higher mass region and for the J/$\psi$ analysis in particular. The main challenge of the pair analysis at these higher masses is to improve the signal to background ratio while losing as little J/$\psi$ signal as possible, so as to keep the advantage of the higher recorded luminosity. Progress in attacking this problem will be discussed.

Speaker: Mr Jeff Klatsky (PHENIX)

16:30 Measurement of Low-Mass Dielectron Production in Pb-Pb Collisions with ALICE

The measurement of electron-positron pairs (dielectrons) in the low invariant mass region allows to study the vacuum and in-medium properties of light vector mesons. Additionally, low-mass dielectrons are produced by internal conversion of virtual direct photons that are emitted during the evolution of ultra-relativistic heavy-ion collisions. They are excellent direct probes to study all collision stages, since they pass through the hot and dense medium almost unscathed. In particular, the extraction of virtual photons in the low-mass region provides a complementary measurement of the real photon yield, which gives access to the temperature of the created matter and can be compared to results from other approaches and existing theoretical calculations. In the ALICE apparatus at the LHC, electrons at mid-rapidity are identified by their specific energy loss in the Inner Tracking System (ITS) and the Time Projection Chamber (TPC), combined with time-of-flight information from the TOF detector. We will present the electron identification performance of these detector systems and the measurement of the low-mass dielectron continuum in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The invariant mass distribution of dielectrons, in slices of pair transverse momentum, will be compared to that of a cocktail of the expected hadronic contributions, with the aim of extracting the virtual direct photon yield.

Speaker: Patrick Simon Reichelt (Johann-Wolfgang-Goethe Univ. (DE))

Slides ALICE-LMEE-PbPb-QM14_poster.pdf

16:30 Measurement of low-mass dielectrons in p-Pb collisions with ALICE

Low-mass dielectrons are an important probe for the hot and dense medium which is created in ultra relativistic heavy-ion collisions. Since leptons do not interact strongly, they carry information from all collision stages with negligible final state interaction. While pp collisions provide a reference measurement for a medium-free environment, the impact of cold nuclear matter effects on the dielectron characteristics can be estimated from p-Pb collisions. In this poster the latest results of the dielectron measurements in minimum bias p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE detector are presented. The measured dielectron mass spectra will be compared to expectations from hadronic sources.

Speaker: Theo Alexander Broker (Johann-Wolfgang-Goethe Univ. (DE))

16:30 Measurement of neutral mesons at high transverse momentum with the ALICE EMCal

One of the physics observables measured with the ALICE Electromagnetic Calorimeter (EMCal) are neutral mesons such as $\pi^0$ and $\eta$ that are reconstructed through their two-photon decay. The EMCal offers a complementary method to the neutral meson measurement with the ALICE tracking system and the PHOS spectrometer. High $p_{\rm T}$ neutral mesons are used to study the modifications of partons in the medium that is created in heavy-ion collisions. In pp and p-Pb collisions, they can be used to study fragmentation functions, and modification of nuclear PDFs in the lead nucleus, respectively. The measurement of high $p_{\rm T}$ neutral mesons is challenging due to various reasons. First, they are a rare probe that requires the use of triggers to collect sufficient statistics for the measurement. Furthermore, the opening angle of the decay photon decreases with increasing transverse momentum and their electromagnetic showers in the detector showers in the detector have a higher probability to overlap. In this analysis, we focus on using separated showers for the neutral meson reconstruction. We will present the current status of high $p_{\rm T}$ neutral meson measurement in the EMCal in pp collisions.

Speaker: Baldo Sahlmuller (Johann-Wolfgang-Goethe Univ. (DE))

Poster QM14_EMCAL_High_pt.pdf

16:30 Measurement of Neutral Pions via their $e^{+}e^{-}\gamma$ Decay in p-Pb Collisions at $\sqrt{s_\rm{NN}}$ = 5.02 TeV with ALICE at the LHC

The study of neutral meson production in p-Pb collisions is of importance to confirm that the strong suppression observed in central Pb-Pb collisions is a final-state effect of the produced dense medium. Furthermore the neutral pion production is essential for the extraction of the direct photon spectra, as it is the main source of background for direct photons. ALICE measures neutral pions using either calorimetry or the photon conversion on the material of inner detectors. The latter is measured in the ITS and TPC detectors for both decays $\pi^{0} \rightarrow \gamma \gamma$ and $\pi^{0} \rightarrow e^{+}e^{-}\gamma$ (Dalitz decay). By comparison with a pp reference scaled to the respective centre-of-mass energy, we determine the nuclear modification factor of neutral pions in p-Pb. In this poster a detailed study of the Dalitz decay channel will be presented. The transverse momentum spectra and the nuclear modification factor of neutral pions, will also be given.

Speaker: Pedro Gonzalez Zamora (Centro de Investigaciones Energ. Medioambientales y Tecn. - (ES)

Slides PosterQM_PedroGonzalez.pdf

16:30 Measurement of non-prompt J/$\psi$ contribution at midrapidity in p-Pb collisions with ALICE

The ALICE experiment at CERN is one of the main LHC experiments and it is dedicated to study the quark-gluon plasma. It is the only experiment that measures the charmonium production at central rapidities ($|y| < 0.9$) down to transverse momenta $p_{\rm T} = 0$ GeV/$c$ in pp, p-Pb, and Pb-Pb collisions. In particular the charmonium state is detected at midrapidity via its e$^+$e$^-$ decay channel. Furthermore, ALICE can separate the non-prompt J/$\psi$ component thus allowing for a measurement of the beauty production down to low $p_{\rm T}$. The results obtained in pp and Pb-Pb will be reviewed. Inclusive J/$\psi$ production has been measured in p-Pb collisions at the center-of-mass energy $\sqrt{s_{\rm NN}} = 5.02$ TeV on an integrated luminosity of $\mu{\rm b}^{-1}$. The status of the analysis of the secondary J/$\psi$ extraction from the inclusive J/$\psi$ yield in p-Pb will be discussed.

Speaker: Annalisa Mastroserio (Universita e INFN (IT))

Slides PosterJpsi_Mastroserio_QM14.pdf PosterJpsi_Mastroserio_QM14.pptx

16:30 Measurement of Nuclear Modifications of Jets in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector at the LHC

Proton-nucleus collisions are utilized to distinguish between initial and final state effects, which is vital for establishing a baseline for heavy-ion collisions. One of the crucial reference measurements is the jet nuclear modification factor ($R_{\rm pPb}$) in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV at the LHC. Jets in ALICE are reconstructed using the anti-k$_{\rm T}$ jet finding algorithm combining information from the Time Projection Chamber (TPC), Inner Tracking System, and the Electromagnetic Calorimeter (EMCal) to measure the charged and neutral jet constituents. In this poster, we discuss in detail the systematic uncertainties on the jet energy scale using the TPC and EMCal in ALICE. Furthermore various techniques to estimate the underlying event in p-Pb collisions will be presented. The jet cross-section and the ratios of jet cross-sections for various radii, sensitive to the jet shape, will be compared to pp and pQCD calculations.

Speaker: Chris G Yaldo (Wayne State University (US))

16:30 Measurement of the ${\rm D^{\ast+}}$ nuclear modification factor in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV in different multiplicity intervals.

At the beginning of 2013, p-Pb collisions at the centre-of-mass energy of 5.02 TeV per nucleon pair have been recorded with ALICE at the LHC. The analysis of D-meson production in p-Pb collisions can provide information on how much the heavy-flavour production in nuclear collisions is influenced by cold nuclear matter effects, such as the nuclear modification of the parton distribution functions and initial-state multiple scatterings. The magnitude of cold nuclear matter effects can be investigated by means of the nuclear modification factor $R_{\rm pPb}$. It is defined as the ratio between the D-meson yield in p-Pb and the yield in pp scaled by the average number of binary collisions. The ALICE Collaboration measured the ${\rm D^{\ast +}}$ multiplicity-integrated $R_{\rm pPb}$ in the central rapidity region in the momentum range $1 < p_{\rm T} < 24$ GeV/$c$, which was found to be compatible with unity and with model calculations including initial state effects. The study of the same observable in different multiplicity intervals provides insight into the dependence of cold nuclear matter effects on the geometry of the collision. However, in p-Pb collisions the connection between the collision geometry and the observed multiplicity through a Glauber approach has proven to be very challenging. Different multiplicity estimators are used to investigate this connection. $ {\rm D^{\ast +} }\rightarrow {\rm D^{0}} \pi^{+} $ decays have been reconstructed in the central rapidity region $| y_{\rm lab}| < 0.8$. In this poster, the multiplicity dependence of the ${\rm D^{\ast+}}$ nuclear modification factor as a function of $p_{\rm T}$ will be presented. Results obtained using different multiplicity estimators will be compared.

Speaker: Grazia Luparello (Universita e INFN (IT))

Poster GLuparello_QM2014_v8.pdf

16:30 Measurement of the Charge Balance Function at RHIC from $\sqrt{s_{\rm NN}}$ = 7.7 to 200 GeV

The balance function, which measures the correlations between opposite sign charge pairs, is sensitive to the mechanisms of charge formation and the subsequent relative diffusion of the balancing charges. The study of the balance function can provide information about charge creation times as well as the subsequent collective behavior of particles. We present charge balance functions in terms of relative pseudorapidity ($\Delta \eta$) from Au+Au collisions at incident energies ranging from $\sqrt{s_{\rm NN}}$ = 7.7 to 200 GeV and compare these results with recent results for Pb+Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV from the ALICE Collaboration [1]. We find that the charge balance function narrows as the collisions become more central and as the incident energy increases. This behavior is consistent with the concept of delayed hadronization of a deconfined quark-gluon plasma (QGP). We also present balance functions in terms of relative rapidity ($\Delta y$) for identified $\pi^{+}/\pi^{-}$ pairs, $K^{+}/K^{-}$ pairs, and $p/\bar{p}$ pairs from central Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. We compare to a model [2] that relates these balance functions to the correlations of deconfined up, down, and strange quarks in the QGP that is created in central Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV. We find our results are consistent with two waves of quark creation in time, one early in the collision ($\sim 1$ fm/$c$) and a second occurring at hadronization ($\sim 5-10$ fm/$c$). We find that the densities of up, down, and strange quarks in the QGP extracted from the model comparison are consistent with current lattice gauge calculations. [1] ALICE Collaboration, Phys. Lett. B **723**, 267 (2013). [2] Scott Pratt, Phys. Rev. Lett. **108**, 212301 (2012), Scott Pratt, Phys. Rev. C **85**, 014904 (2012).

Speaker: Gary Westfall (Michigan State University)

Poster WestfallQM14Poster_v7.pdf

16:30 Measurement of the inelastic proton-lead cross section at 5.02 TeV/nucleon center-of-mass energy with CMS

Total cross sections in pp, p$\bar{\rm p}$, ep collisions at high energies have been described in terms of pomeron exchange. Their increase with energy depends on the parton evolution mechanism. Proton-nucleus cross sections have so far only been measured in fixed-target or cosmic-ray experiments. CMS has measured the total inelastic proton-lead cross-section by detecting activity in the forward calorimeters. The luminosity determination is based on van der Meer scans with a precision of 3.5%. The cross section visible within the CMS acceptance is extrapolated to the full phase space yielding the value of 2.06±0.08 barns at 5.02 TeV/nucleon center-of-mass energy. Using the previously measured cross section of pp collisions, this result is used to test the Glauber model at TeV energies. Implications for cosmic ray studies will also be discussed.

Speaker: Dr Gabor Veres (CERN)

Poster posterQM14vg2.pdf

16:30 Measurement of the space-time extent of the emission source in d+Au and Au+Au collisions through charged pion interferometry at $\sqrt{s_{NN}}=200$ GeV

The recent observation of azimuthal correlations in p+Pb collisions at LHC is consistent with an interpretation as either an initial state gluon saturation effect or the expansion dynamics of a QGP like medium. It is well known that the latter process is characterized by strong final state re-scattering effects. In this work two-pion interferometry measurements in d+Au and Au+Au collisions at √sNN = 200 GeV are performed to extract and compare the Gaussian source radii Rout, Rside and Rlong, which characterize the space-time extent of the emission sources. The comparisons which are carried out as a function of collision centrality and the mean transverse momentum for pion pairs, indicate strikingly similar patterns for the d+Au and Au+Au systems. They also indicate linear dependence of Rside on the initial traverse geometric size, as well as a smaller freeze-out size for the d+Au system. These patterns point to the important role of final-state re-scattering effects in the reaction dynamics of d+Au collisions.

Speaker: Nuggehalli Ajitanand (SUNY Stony Brook)

Poster AjitQM14Post.pdf

16:30 Measurement of transverse momentum jet spectra in Pb-Pb collsions at $\sqrt{\rm s_{NN}}$ = 2.76 TeV using calorimeter triggers with the ALICE detector

In relativistic heavy-ion collisions a hot, dense medium of strongly interacting matter called the Quark-Gluon Plasma (QGP) is formed. It has been determined that jets of hadrons, created from the fragmentation of hard-scattered partons, are suppressed relative to measurements from proton-proton collisions. This jet quenching effect in both strong and weak coupling calculations explicitly depends on the path-length of the parton through the medium. Jets can be reconstructed in the ALICE detector from the tracking systems alone, creating charged jets, or from the combination of the tracking systems and the electromagnetic calorimeter (EMCal). The EMCal was used to trigger on events with a jet within its acceptance, which allows for a measurement of the jet spectra versus centrality and event plane by increasing the available statistics. The centrality and event plane of these events are reconstructed with the VZERO detectors to avoid autocorrelations with the triggered jets. Triggers introduce biases to both the fragmentation of the jets, and to the background. Centrality and event plane dependence of the measured spectra and the background using the EMCal trigger will be shown as well as the reconstruction and correction procedures with the trigger biases.

Speaker: Rosi Jan Reed (Yale University (US))

Slides RReedQM2014Posterv5.pdf

16:30 Measurements Of Non-Photonic Electron Production And Correlation With STAR Experiment

Heavy quarks, primarily produced in initial hard scattering processes at the Relativistic Heavy Ion Collider (RHIC), are important tools for understanding the properties of the Quark-Gluon Plasma (QGP). The heavy quark interaction with the QGP can be studied through non-photonic electrons (NPE), which are produced from semi-leptonic decays of heavy flavor mesons. In $p+p$ collisions measurements of heavy flavor production serve as a test of the pQCD framework and are used as a baseline for comparison to measurements from heavy ion collisions. In $Au+Au$ and $d+Au$ the hot and cold nuclear matter effects can be quantified through the nuclear modification factors ($R_{AA}$, $R_{dA}$). Models with different assumptions describe relatively well the suppression and elliptic flow of NPE at the top RHIC energy. New observables are required to discriminate between models. An energy dependence of $R_{AA}$ and elliptic flow $v_2$ and correlations of non-photonic electrons to hadrons can be used to further probe the interaction of heavy quarks with the medium. In this talk, we will present a new measurement of NPE production in p+p collisions at $\sqrt{s}=200$ GeV in a broad transverse momentum range (0.4< $p_{T}$ < 12 GeV/c). We will discuss the energy dependence of NPE production and azimuthal anisotropy measurements in Au+Au collisions at $\sqrt{s_{NN}}$ =39, 62.4 and 200 GeV. Nuclear modification factor $R_{AA}$ in Au+Au collisions and $R_{dA}$ in d+Au collisions at $\sqrt{s_{NN}}=200$ GeV will be presented too. Finally we will show NPE-hadron correlations in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV at midrapidity.

Speaker: Mrs Olga Rusnakova (Czech Technical University in Prague)

Poster QM_NPE_poster_Rusnakova.pdf

16:30 Measurements of the correlation between heavy-flavour decay electrons and charged particles in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC

The aim of relativistic heavy-ion collisions is to investigate the properties of the Quark-Gluon Plasma (QGP), a deconfined state of strongly-interacting matter. The characterisation of the QGP via the measurements of several observables is the main purpose of the ALICE detector at the CERN LHC. Heavy quarks, i.e. charm and beauty, are a very useful tool in this context. Due to their large masses, they are produced in initial hard parton-parton scattering processes at the very early stages of the collision. Therefore, they experience the whole medium evolution and carry information on the QGP properties. The production of open heavy-flavour hadrons can be measured with ALICE via their hadronic and semi-electronic decays at mid-rapidity and via their semi-muonic decays at forward rapidity. In this poster emphasis will be put on the measurements of the correlation, in azimuth ($\Delta\varphi$) and pseudorapidity ($\Delta\eta$), between the electrons from heavy-flavour hadron decays and the charged particles produced in the collision. The comparison of the correlation in pp, p-Pb and Pb-Pb collisions, at various centralities, can provide information on the medium properties. Particularly, correlations of long-range in $\Delta\eta$ were recently observed in high-multiplicity p-Pb collisions at the LHC energies. Furthermore, in pp collisions, the relative contributions of beauty and charm decays to the total electron yield can be evaluated by comparing the measured correlation function with the predictions from PYTHIA simulations. Measurements of the correlation function between electrons and charged particles in pp ($\sqrt{s} = 2.76$ and $7$ TeV), Pb-Pb ($\sqrt{s_{\rm{NN}}} = 2.76$ TeV), and p-Pb collisions ($\sqrt{s_{\rm{NN}}} = 5.02$ TeV) will be presented.

Speaker: Elienos Pereira De Oliveira Filho (Universidade de Sao Paulo (BR))

Poster 2014-May-18-conferencefile-poster_v6.pdf

16:30 Medium effects on the transport coefficients of a hot pion gas

The shear and bulk viscosities, as well as the thermal conductivity of a pion gas are obtained by solving the relativistic transport equation in the Chapman-Enskog approximation at finite temperature with a finite chemical potential. Instead of estimating the scattering amplitute from the lowest order Lagrangian of chiral perturbation theory used in most of the literature, we have modelled the pion-pion interaction cross section by introducing rho and sigma meson propagator, which agrees well with the experimental value. The in-medium effects are then introduced in the $\pi\pi$ cross section through one-loop self-energies of the exchanged $\rho$ and $\sigma$ mesons. The effect of early chemical freeze-out in heavy ion collisions is implemented through a temperature-dependent pion chemical potential, which increases with decreasing temperature. These shows a noticeable effect in the temperature dependence of the viscosities and thermal conductivity. Finally the ratios of the viscosities over entropy density also has been depicted where the entropy density is also corrected for an interacting system.

Speaker: Mrs Sukanya Mitra (Variable Energy Cyclotron Centre)

Poster QM-Sukanya-Poster.pdf

16:30 Medium response in asymmetric di-jet events from full 3-D hydro

We develop a fully (3+1)-dimensional relativistic hydrodynamic model with source terms to analyze large angle emission of low-$p_{T}$ particles in asymmetric di-jet events. In Pb-Pb collision experiments at LHC, a large number of low-$p_{T}$ hadrons at large angles from a sub-leading jet is observed in asymmetric di-jet events by the CMS Collaboration [1]. The total transverse momentum of the leading-jet balances that of the sub-leading jet together with the low-$p_{T}$ particles spread over wide angles from sub-leading jet axis.Motivated by the experimental fact, we analyze asymmetric di-jet events to understand the transport dynamics of the transverse momentum balance in the three-dimensionally expanding QGP. The space-time evolution of the quark-gluon plasma (QGP) realized experimentally in heavy ion collisions at collider energies is well described by relativistic hydrodynamics. High energy partons are also produced through initial hard scatterings and have to traverse the QGP fluid. The energy and momentum of these traversing partons are lost in the medium through strong interaction between them. Thus jet quenching phenomena provide an important clue to extract one of the substantial properties of the QGP, namely stopping power against energetic partons. The question then arises, ``Where and how do these lost energies and momenta diffuse inside the medium?" Suppose deposited energy and momentum are quickly equilibrated, the traversing jet particles induce the collective flow in the QGP fluid. On the other hand, the background QGP fluid is by no means static, but expands itself at relativistic velocity. As a consequence, the collective flow results from the interplay of expansion of background QGP fluid and wake induced by jets. This is the first attempt to numerically solve relativistic hydrodynamic equations with source terms without linearization in fully (3 + 1)-dimensional Milne coordinates. In the hydrodynamical equations, the source terms are introduced to account for the energy-momentum deposition from the energetic partons. It is shown that Mach cone-like structures are formed in the medium and distorted strongly by radial flow of the expanding background QGP fluid. As a result, we find that the low-$p_{T}$ enhancement at large angles from the quenched jet compensates exactly the di-jet $p_{T}$-imbalance, similar to that observed by the CMS. Therefore these low-$p_{T}$ particles spread over wide angle are originated from deposited energy and momentum transported by the collective expansion of the QGP. [1] S. Chatrchyan *et al.* [CMS Collaboration], Phys. Rev. C **84**, 024906 (2011); C. Roland, J. Phys. G **38**, 124020 (2011). [2] Y. Tachibana and T. Hirano, Nucl. Phys. A904-905 **2013**, 1023c (2013).

Speaker: Mr Yasuki Tachibana (The University of Tokyo)

Poster tachibana_QM14_poster.pdf

16:30 Meson production in nucleon-nucleon collisions

We study the production of mesons in nucleon-nucleon reactions at center-of-mass momenta of a few GeV using an $N_f=2$ linear sigma model, extended by including the $N_f=2$ multiplets of (pseudo-) scalar and (axial-) vector mesons and a doublet of the nucleon together with its chiral partner (the $N^*(1535)$ or $N^*(1650)$ resonance). Cross sections for the production of $\pi-$, $\eta-$, $\rho-$ and $\omega-$mesons will be presented. The results are compared to experimental data.

Speaker: Khaled Teilab (Institut für Theoretische Physik - Universität Frankfurt)

Poster QM14-2.pdf

16:30 Meta-stable States in Quark-Gluon Plasma

We study the meta-stable states in high temperature phase of QCD characterised by nonzero expectation values for the imaginary part of the Polyakov loop. We consider $N_f= 2, 3$ dynamical staggered quarks, and carry out simulations at various values of the coupling $\beta$ to observe these states. In particular, we find the value of the coupling ($\beta_m$) above which the meta-stable states appear. The resulting value of $\beta_m$ corresponds to temperature $T_m\gtrsim 750$MeV for $N_f=2$.

Speaker: Dr Ananta P. Mishra (Physical Research Laboratory, Ahmedabad)

16:30 Midrapidity antibaryon-to-baryon ratios in Pb-Pb and p-Pb collisions measured by the ALICE experiment

The ALICE Experiment features low material budget and high resolution tracking, which allow for precise measurements of charged particle production. The measurement of the antibaryon-to-baryon ratios ($\overline{\rm{B}}$/B), in particular, probes the baryon transport and degree of baryon stopping in high energy interactions, providing insight into the collision dynamics and the structure of baryons. In this poster I will discuss the measurement of different ($\overline{\rm{B}}$/B) ratios ($\overline{\rm p}/{\rm p}$, $\overline{\Lambda}/{\Lambda}$, ${{\overline{\Xi}}^{+}}/{\Xi^{-}}$, ${{\overline{\Omega}}^{+}}/{\Omega^{-}}$) in Pb-Pb at $\sqrt{s_{\rm NN}} = 2.76$ TeV and p-Pb at $\sqrt{s_{\rm NN}} = 5.02$ TeV as a function of the charged particle multiplicity density, rapidity and transverse momentum. Results from Pb-Pb and p-Pb are presented and compared to models.

Speaker: Michal Meres (Comenius University (SK))

Slides posterQMv5.pdf

16:30 Multi parton interaction studies in pp and p-Pb

Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in pp collisions at a centre of mass energy of $0.9$, $2.76$, $7$ TeV and in p-Pb collisions at a nucleon-nucleon centre of mass energy of $5.02$ TeV. The particle correlations are expressed as an associated yield per trigger particle in the transverse-momentum range $0.7 < p_{\rm T}, assoc < p_{\rm T}, trig < 5.0$ GeV/$c$, to include jets down to the lowest energy (minijets). In p-Pb collisions, long-range near-side correlations, projected onto the azimuthal angle difference, are subtracted from both near- and away-side short-range correlations in order to remove the non-jet-related components, namely the double-ridge. Near- and away-side per trigger yields are studied as a function of the charged particle multiplicity at mid-rapidity. The extracted yields provide information about parton fragmentation at low transverse momenta, as well as about the contribution of multiple parton interactions (MPIs) to particle production. We find that in pp collisions the uncorrelated seeds stagnate at high multiplicity, showing a limit in the number of MPIs. On the contrary, in p-Pb they increase linearly with multiplicity. Further, moving from multiplicity to geometry parameters, we observe the expected scaling of MPIs with Glauber $\rm N_{coll}$ only in the intermediate Glauber $\rm N_{coll}$ region, revealing a bias in the number of hard scatterings when estimated from the Glauber model.

Speaker: Emilia Leogrande (University of Utrecht (NL))

Slides poster_full.pdf

16:30 Multiple Freezeout in Heavy Ion Collisions

We argue that known systematics of hadron cross sections may cause different particles to freeze out of the fireball produced in heavy-ion collisions at different times. We find that a simple model with two freezeout points is a better description of data on hadron yields than that with a single freezeout, while still remaining predictive. The resulting fits seem to present constraints on the late stage evolution of the fireball. We also study the implication of such a freezeout scenario on the susceptibilities of the conserved charges and the thermal production of light nuclei and antinuclei.

Speaker: Sandeep Chatterjee (National Institute of Science Education and Research)

16:30 Multiplicity and s Dependence of Hadron Spectra in pp Collisions at RHIC and LHC

Fragmentation functions measured in e+e- and pp collisions are well reproduced via a fragmentation model based on microcanonical statistics and superimposed Euler--Gamma-type multiplicity fluctuations [1,2]. The power of the obtained analytic fragmentation function (which is a cut-power function in x) developes a double-logarithmic dependence on the QCD scale Q^2 [3]. Besides, this function also describes transverse hadron spectra measured in pp and AA collisions at RHIC and LHC energies [4,5]. Interestingly, the power of the spectra of pions, kaons and protons stemming from pp collisions exhibits a similar double-logarithmic dependence on the collision energy sqrt{s} and on the hadron multiplicity N (measured in the |eta|<1 region) [6]. [1] K. Urmossy etal, Phys. Lett. B, 718 (2012) 125-129, arXiv:1204.1508 [2] K. Urmossy etal, Phys. Lett. B, 701 (2011) 111-116, arXiv:1101.3023 [3] G. G. Barnafoldi etal, Gribov 80 Conference: C10-05-26.1, p.357-363 [4] K. Urmossy etal, Phys. Lett. B, 689 (2010) 14-17, arXiv:0911.1411 [5] G. G. Barnafoldi etal, 'Hot Quarks 2010', J. Phys. Conf. Ser. 270 (2011) 012008 [6] K. Urmossy, Submitted to EPJC, arXiv:1212.0260

Speaker: Karoly Uermoessy (Hungarian Academy of Sciences (HU))

Poster UKqm2014_3.pdf

16:30 Multiplicity dependence of ${\rm D}^{*+}$-meson production in p-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV at the LHC

ALICE's heavy-ion programme is dedicated to the study of the hot, high-density state of matter formed in high-energy nuclear collisions. One of the many probes at its disposal is the production of heavy quarks, namely charm and beauty, since due to their large masses they are produced in the earliest stages of the collision and experience the full evolution of the system. As well as studying the production of leptons from heavy-flavour decays, ALICE's excellent tracking and vertexing capabilities also allow us to fully reconstruct the hadronic decays of the open-charmed D mesons. In order to disentangle experimental outcomes arising in the hot and dense medium from those occurring due to cold nuclear matter effects, it is also necessary to make measurements in p-Pb collisions. One measurement that can be made in this system is the yield of certain particle species as a function of the multiplicity of charged particles produced in the collisions. Such measurements allow us to investigate the role of multi-parton interactions in proton-nucleus collisions at LHC energies, in particular when compared to similar results in pp collisions. Previous ALICE studies in the charm sector have already found that the production of J/$\psi$ mesons in pp collisions at $\sqrt{s}=7$ TeV exhibits an increasing yield per event with increasing multiplicity. Similar measurements have also been made for D-meson production in pp collisions. In this poster, we present the ALICE measurements of D$^{*+}$-meson production as a function of charged-particle multiplicity in p-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV.

Speaker: Jeremy Wilkinson (Ruprecht-Karls-Universitaet Heidelberg (DE))

Poster jwilkinson_dstvsmult_poster_qm2014.pdf

16:30 Multiplicity dependence of long and short-range two-particle correlation in $\sqrt{s}$ = 7TeV proton-proton collisions at LHC-ALICE experiment

Previously observed ridge-like structures in high-energy heavy-ion collisions has mostly been explained by event anisotropy of the initial geometrical distribution of participants, followed by collective expansion. Fluctuations of the initial geometry are known to become more and more significant in peripheral collisions, while the collective expansion should become stronger in semi-central to central collisions. High-multiplicity pp collisions may provide important information on ridge-like structure in small- and high density-system or possible source of collectivity. The $\Delta\varphi$-$\Delta\eta$ correlation has been measured with central and forward detectors in pp collisions at $\sqrt{s}$ = 7 TeV with the ALICE detector, jet shapes at $\Delta\varphi\approx$ 0, $\Delta\eta\approx$ 0, and $\Delta\varphi\approx \pi$ and ridge-like structure in $\mid\Delta\eta\mid > 1.5$. The presence of long-range $\Delta\eta$ correlations in pp collisions will be investigated and the potential biases using different combinations of forward and central barrel detectors will be discussed.

Speaker: Jihyun Bhom (University of Tsukuba (JP))

16:30 MUSIC and MARTINI with a Hadronic Afterburner

We present our improved event generator for heavy ion collisions which combines MUSIC, MARTINI and UrQMD. This combines hydrodynamic evolution QGP starting with the IP-Glasma and MC-Glauber initial conditions (MUSIC), jet production and propagation through the evolving medium (MARTINI) and the final hadronic interactions of the bulk and jet particles using the UrQMD. The result is generation of full events for relativistic heavy ion collisions consistently including both the soft and hard physics of each event. In this talk, we will present our first results on jet quenching, high and low $p_T$ di-hadron correlations, and effects on $v_2$ and $v_3$ with an emphasis on the difference between the IP-Glasma and the MC-Glauber initial conditions. These calculations will be compared to recent RHIC and the LHC data and implications for future work will be discussed.

Speaker: Sangwook Ryu (McGill University)

Poster Poster_RYU.pdf

16:30 Neutral meson measurement via photon conversions in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the LHC

The measurement of particle production in p-Pb collisions at high LHC energies allows the study of fundamental properties of quantum chromodynamics (QCD) at low parton momentum fraction $x$ and high gluon densities. Moreover it is important as reference for heavy ion collisions. It can show whether the initial state of the colliding nuclei plays a role in the observed suppression of hadron production at high $p_{\rm T}$ in Pb-Pb collisions. The measurement of neutral pions has the advantage of large statistics of identified particles over a relatively large transverse momentum range. In addition, the neutral pion measurement is crucial for the background determination for other analyses like the direct photon measurement. With the ALICE setup it is possible to measure neutral pions with different methods: via its two photon decay channel using calorimeters or photon conversions or via its Dalitz decay channel. This poster will show the results of the $\pi^{0} \rightarrow \gamma \gamma$ and $\eta \rightarrow \gamma \gamma$ analysis using photon conversions. Differential invariant cross sections for minimum bias collisions and for different charged particle multiplicities will be presented for both mesons as well as $R_{\rm pPb}$ for the neutral pions.

Speaker: Annika Passfeld (Westfaelische Wilhelms-Universitaet Muenster (DE))

Slides 2014-May-15-conferencefile-Poster_QM2014_AnnikaPassfeld_v4.pdf

16:30 Neutral Pions Measured in the ALICE Electromagnetic Calorimeter in pp and p-Pb Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

Light neutral mesons are among the most plentiful particles produced at the LHC and therefore serve as an ideal testing ground for pQCD in both pp and A-A collisions. Additionally, they provide a critical foundation upon which other analyses (direct photon, dilepton, etc) base their background determination. The nuclear modification factor $R_{\mathrm{AA}}$ shows a dramatic suppression in heavy ion collisions with respect to the pp baseline expectation presumably due to the formation of quark-gluon plasma (QGP). However, in order to disentangle how much of this phenomenon is simply a result of effects from "cold" nuclear matter in the initial state, p-A collisions are a necessary and useful control measurement. The ALICE electromagnetic calorimeter (EMCal) encompasses a large geometric acceptance of 100 degrees in azimuth and $|\eta|<0.7$ in pseudorapidity leading to a high statistics dataset. $\pi^{0}$ production is measured via the diphoton decay channel in pp collisions at $\sqrt{s} = 2.76~$TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~$TeV. The status of the analysis of the differential invariant cross section for neutral pions as well as $R_{\rm pPb}$ will be presented for various centralities measured in the EMCal.

Speaker: Jason Adrian Kamin (Johann-Wolfgang-Goethe Univ. (DE))

16:30 New beam line and experiments at J-PARC

A new beam line is under construction at the Hadron Experimental Facility of the Japan Proton Accelerator Research Complex (J-PARC). Details of the beam line and proposed experiments using the beam line are reported in this talk. A new beam line will deliver a primary 30 GeV proton beam and a secondary produced un-separated hadron (mainly pion) beam. Intensities of the beams are $10^10$ Hz and $10^8$ Hz, respectively. The momentum of the secondary beam is up to 20 GeV/c. The first experiment using the beam line is under preparation to study mass properties of vector mesons and partial chiral symmetry restoration in nuclear medium. The experiment will measure mass spectra of vector mesons in nucleus with 100 times larger statistics than the KEK-PS E325 experiment which shows significant mass modifications in nucleus. The new experiment aims to confirm results of the previous KEK experiment and have a large statistics to discuss more details. The new experiment uses new detector techniques, such as a GEM tracker and a Hadron Blind Detector, to achieve such a large statistics.

Speaker: Prof. Kyoichiro Ozawa (KEK)

Slides K_Ozawa_qm2014.pdf

16:30 New results in the formalism and application of relativistic viscous hydrodynamics

We derive relativistic viscous hydrodynamic equations for various forms of the non-equilibrium single-particle phase-space distribution function $f(x,p)$, and apply these results to relativistic heavy-ion collisions at the RHIC and LHC energies. In the first part of this work, we derive hydrodynamic equations invoking the generalized second law of thermodynamics for two different forms of $f(x,p)$ within Grad's 14-moment approximation. We find that the relaxation times in these two derivations are identical for shear viscosity but different for bulk viscosity. These equations are used to study thermal dilepton and hadron spectra within longitudinal scaling expansion of the matter formed in relativistic heavy-ion collisions. For consistency, the same $f(x,p)$ is used in the particle production prescription as in the derivation of the viscous evolution equations. Appreciable differences are found in the transverse-momentum spectra corresponding to the two forms of $f(x,p)$. We emphasize that an inconsistent treatment of the non-equilibrium effects influences the particle production significantly, which may affect the extraction of transport properties of quark-gluon plasma [1]. In the second part, we consider an alternative Chapman-Enskog-like method, which unlike the widely used Grad's method, involves a small expansion parameter. We derive an expression for $f(x,p)$ to second order in this parameter. We show analytically that while Grad's method leads to the violation of the experimentally observed $1/\sqrt{m_T}$ scaling of the longitudinal femtoscopic radii, the alternative method does not exhibit such an unphysical behavior. We compare numerical results for hadron transverse-momentum spectra and femtoscopic radii obtained in these two methods, within the one-dimensional scaling expansion scenario. Moreover, we demonstrate a rapid convergence of the Chapman-Enskog-like expansion up to second order. This leads to an expression for $\delta f(x,p)$ which provides a better alternative to Grad's approximation for hydrodynamic modelling of relativistic heavy-ion collisions [2]. [1] R.S. Bhalerao, A. Jaiswal, S. Pal, and V. Sreekanth, Phys. Rev. C88 (2013) 044911. [2] R.S. Bhalerao, A. Jaiswal, S. Pal, and V. Sreekanth, e-Print: arXiv:1312.1864 [nucl-th].

Speakers: Amaresh Jaiswal (Tata Institute of Fundamental Research), Rajeev Bhalerao (Tata Institute of Fundamental Research), Sreekanth V. (Tata Institute of Fundamental Research), Subrata Pal (Tata Institute of Fundamental Research)

Poster poster-QM-2014-corr.pdf

16:30 New results on hadron spectra in Be+Be collisions from NA61/SHINE at the CERN SPS

The NA61/SHINE experiment performs a detailed study of the onset of deconfinement and search for critical point of strongly interacting matter by colliding nuclei of different sizes (protons, Be, Ar, Xe and Pb) at various beam momenta in the SPS energy range. The study of the onset of deconfinement is carried out by comparing inclusive hadron spectra from the recent Be+Be data taking campaign to the NA61/SHINE reference results on p+p interactions, as well as Pb+Pb data from the NA49 experiment. The new Projectile Spectator Detector (PSD) allows for excellent centrality measurement and determination of projectile spectator number with one nucleon precision in a model independent way. First evidence for collectivity in Be+Be collisions is observed based on the transverse mass spectra of negatively charged pions. The spectra are corrected for detector effects, as well as feed-down from weak decays and secondary interactions. The shape of the mid-rapidity transverse mass spectrum in central Be+Be collisions is non-exponential in the soft regime. This feature, also observed in the Pb+Pb data, may indicate transverse collective effects in Be+Be collisions. The analysis of Be+Be data allows to extract the mean multiplicity of negatively charged pions from the rapidity spectrum and normalize it to the mean number of wounded nucleons. The results are compared with the corresponding ones obtained for p+p and central Pb+Pb collisions.

Speaker: Emil Aleksander Kaptur (University of Silesia (PL))

16:30 News on transverse momentum fluctuations in p+p and Be+Be energy scans from NA61/SHINE

The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. These goals are to be achieved by performing a two dimensional phase diagram ($T$-$\mu_B$) scan by measurements of hadron production properties in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of collision energy and system size. Close to the critical point increase of fluctuations is predicted. In this contribution preliminary results on transverse momentum fluctuations expressed in terms of strongly intensive quantities ($\phi$, $\Sigma$ and $\Delta$) from the p+p and Be+Be energy scans will be presented. The data is fully corrected for experimental biases using the novel fluctuation analysis method. The NA61/SHINE results will be compared with NA49 data on central Pb+Pb collisions and model predictions.

Speaker: Tobiasz Czopowicz (Warsaw University of Technology (PL))

Poster TC-QM2014-poster.pdf

16:30 Noncongruence of the deconfinement phase transition

First-order phase transitions (PTs) with more than one globally conserved charge, so-called noncongruent PTs, have characteristic differences compared to congruent PTs (e.g., dimensionality of phase diagrams and location and properties of critical points and end points). In this talk we investigate the noncongruence of the deconfinement PT and compare it with the nuclear liquid-gas PT at subsaturation densities. The used equation of state is calculated from the chiral SU(3) model, which is one of the few models for the deconfinement PT, which contains quarks and hadrons in arbitrary proportions (i.e., a “solution”) and gives a continuous transition from pure hadronic to pure quark matter above a critical point. The study shows the universality of the applied concept of noncongruence for the two PTs and illustrates the different typical scales involved. In addition, we find a principle difference between the liquid- gas and the deconfinement PTs: in contrast to the ordinary Van-der-Waals-like PT, the phase coexistence line of the deconfinement PT has a negative slope in the pressure-temperature plane. As another qualitative difference we find that the noncongruent features of the deconfinement PT become vanishingly small around the critical point.

Speaker: Matthias Hempel (Basel University)

Poster hempel_qm2014.pdf

16:30 Nonextenisve Quark Recombination Model

We developed a nonextensive quark recombination model to study the matter created in relativistic heavy ion collisions. We use the temperature, flow velocity and the nonextensive parameter q as our model parameters. To study the collisions energy and centrality dependance of our model parameters, we fit the transverse momentum spectra of different hadrons at RHIC and LHC. Comparison between our model calculations and blast wave model is shown.

Speaker: Dr Mohamed Abdel-Aziz (Ain Shams University)

16:30 Nonlinear waves in 2nd order conformal hydrodynamics

In this work we study wave propagation in dissipative relativistic fluids described by a simplified set of the conformal 2nd order hydrodynamic equations. Small amplitude waves are studied within the linearization approximation while waves with larger amplitude, which are described by nonlinear wave equations, are investigated using the reductive perturbation method. Our results indicate the presence of a ``soliton-like'' wave solution in 2nd order conformal hydrodynamics despite the presence of dissipation and relaxation effects.

Speaker: Hugo Marrochio (U)

Poster poster12.pdf

16:30 Nonperturbative effect on the melting of quarkonium

We have investigated the properties of quarkonia in a complex potential which is obtained by the in-medium corrections to both the perturbative and nonperturbative term in the potential through the dielectric function in real-time formalism. In isotropic medium, the real-part of the potential becomes stronger and thus makes the quarkonia more bound whereas the (magnitude) imaginary-part too becomes larger and thus contribute more to the thermal width, compared to the in-medium correction of the Coulomb term alone. With these cumulative observations, we studied the dissociation where a resonance is said to be dissolved in a medium when its binding energy decreases with temperature and eventually becomes equal to its width and have found that the bound states are now dissociated at higher temperature, in the absence of nonperturbative term. Finally we extend our calculation to a medium which exhibits a local momentum anisotropy and calculate both the real- and imaginary-part of potential, by the leading anisotropic corrections to the propagators. The presence of anisotropy makes the real-part of the potential more stronger while the imaginary-part is weakened slightly and hence width of a particular resonance becomes narrower, compared to an isotropic medium. However, since the temperature corrections to the imaginary-part is a small perturbation to the vacuum part, so overall the anisotropy makes the dissociation temperatures higher, compared to isotropic medium.

Speaker: Dr Binoy Krishna Patra (Indian Institute of Technology Roorkee)

Poster posterqm2014.pdf

16:30 Nonperturbative gluonic three-point correlations

The correlation functions of QCD are the fundamental building blocks for hadron phenomenology and strong-interaction matter studies based on functional continuum methods. A better understanding of these correlations from first principles constrains the input of more phenomenological studies. Here, we report on the first self-consistent solution of the Dyson-Schwinger equation (DSE) for the three-gluon vertex [1]. Based on our earlier results for the propagators [2] which match data from lattice Monte-Carlo simulations, we obtain kinematically complete results for the three gluon vertex that are in very good agreement with available lattice data likewise. Feeding these results back into the propagator DSEs allows us to assess previously used model input and approximations. The full iterative solution to the coupled DSEs of pure Landau gauge QCD without quarks, which now for the first time dynamically includes the complete set of three-point vertex functions, then provides encouraging evidence of the convergence of this type of vertex expansion for QCD. [1] Blum, Huber, Mitter, von Smekal, arXiv:1401.0713 [hep-ph] [2] Huber, von Smekal, JHEP 1304 (2013) 149

Speaker: Dr Markus Huber (KFU Graz)

Poster Darmstadt2014a_online.pdf

16:30 Novel sub-jet observables for quenched jets

At present jet quenching observations rely on samples that contain a mixture of quenched and unquenched jets. Modifications of the structure of jets due to quenching are explored by considering jet sub-structure in event generators: MC PYTHIA (vacuum jets) and Q-PYTHIA (in-medium modified jets). Subjet observables are defined in collinear and infrared safe algorithms and tested for exprimental use in heavy-ion collisions.

Speakers: Guilherme Teixeira De Almeida Milhano (Universidade de Santiago de Compostela (ES)), Liliana Marisa Cunha Apolinario (Universidade de Santiago de Compostela (ES)), Mateusz Ploskon (Lawrence Berkeley National Lab. (US)), Xiaoming Zhang (Lawrence Berkeley National Lab. (US))

Poster SubjetsPoster.pdf

16:30 Nuclear matter with the functional renormalization group

We study a chiral nucleon-meson model, which turns out to be perfectly suited to analyze both the thermodynamics of nuclear matter and chiral symmetry breaking. The model is extended by a self-consistent treatment of fluctuations with methods of the functional renormalization group. The results are in good agreement with thermodynamical calculations in the framework of in-medium chiral effective field theory. In addition, there is no hint of a chiral phase transition for temperatures below 100 MeV and densities below about twice the nuclear saturation density. Next, the model is extended to asymmetric nuclear matter. The neutron matter equation of state is studied. It is found to satisfy the constraints from the observation of two-solar mass neutron stars.

Speaker: Mr Matthias Drews (TUM, Munich)

Poster poster.pdf

16:30 Nuclei identification and hypernuclei reconstruction with the ALICE inner tracker upgrade

One of the striking features of particle production in Pb-Pb collisions at high energies is the near equal abundance of matter and antimatter in the central rapidity region. The comparison of the production of light nuclei, antinuclei, hypernuclei and anti--hypernuclei at high energies offers a unique opportunity to understand if the mechanism of particle production in ultra-relativistic heavy ion collisions can be described by a coalescence or a thermal model. An upgrade of the ALICE apparatus is scheduled for the second long LHC shutdown (LS2) in 2019 and it will give access to otherwise unreachable processes. The new Inner Tracking System (ITS), with largely enhanced tracking precision and efficiency, and the improved readout capability of most of the ALICE detectors will be crucial for the measurement of light (anti)hypernuclei. The identification of light nuclei is also important for the reconstruction of the weak decays of hypernuclei in which a nucleus and a pion are emitted with a V0--like topology. A method for tagging light nuclei with the new ITS, using the information on the size of the produced pixel clusters was developed. The study of the $\mathrm{^{3}_{\Lambda}H} \rightarrow \mathrm{^{3}He} + \pi^{-}$ decay channel has been carried out using a detailed simulation of the new ITS. The expected yield, signal-to-background ratio and significance have been determined taking into account the target integrated luminosity of 10 nb$^{-1}$ for the ALICE upgrade programme.

Speaker: Stefania Bufalino (Universita e INFN (IT))

Slides PosterQM2014_Bufalino_v3.pdf

16:30 Number of Quark Participant Scaling of $\langle dN_{ch}/d\eta \rangle$ and $\langle dE_{T}/d\eta \rangle$ with Centrality for 200 GeV d+Au Collisions and Au+Au Collisions from 7.7 to 200 GeV

The dependence of charged particle production and transverse energy production in relativistic heavy ion collisions has been comprehensively studied as a function of $\sqrt{s_{NN}}$ from 7.7 to 200 GeV and centrality represented as the average number of nucleon participants, $\langle N_{part} \rangle$, in the collision. The general trend of the data exhibits a decrease in the value of $\langle dN_{ch}/d\eta \rangle$ and $\langle dE_{T}/d\eta \rangle$ at mid-rapidity normalized by the number of participant pairs as $\langle N_{part} \rangle$ decreases. However, it has been demonstrated that identified particle flow data scales with the number of constituent quarks over a large range of collision energies, so the number of quark participants may be a more appropriate scaling variable for particle production. The average number of quark participants, $\langle N_{qp} \rangle$, as a function of centrality is estimated using a modified Glauber model that replaces each nucleon participant with quark participants. This estimate is then used to investigate the $N_{qp}$-scaling of $\langle dN_{ch}/d\eta \rangle$ and $\langle dE_{T}/d\eta \rangle$ using PHENIX data for 200 GeV d+Au collisions and for Au+Au collisions at $\sqrt(s_{NN})=$ 200, 62.4, 39, 27, 19.6, and 7.7 GeV with special emphasis on the validity of scaling with $\langle N_{qp} \rangle$ at the lower energies.

Speaker: Jeffery Mitchell (Brookhaven National Laboratory)

Poster qm2014poster-mitchell.pdf

16:30 Observable consequences of tilted initial state

The hydrodynamic simulations of the ultra-relativistic heavy ion collisions are very successful in describing these reactions, as it is confirmed by the latest RHIC and LHC data. Hydrodynamic simulation does not only mean a certain algorithm of solving the equations of relativistic hydrodynamics; it is also based on a specific initial state, specific EoS, and specific freeze out realization. In our opinion, between these elements the least controlled is the initial state. Unfortunately at the moment there is no unambiguous model describing the formation of locally thermalized initial states of energetic heavy ion collisions, and thus, all initial states in use are either completely phenomenological or contain some phenomenological elements. We will argue that, from the very general principles like linear and angular momentum conservation, we can expect to form tilted and rotating initial state. The latter is particularly important for ultra-high LHC energies. The key question we address is what are the observable consequences of such a tilted and rotating initial state? For detailed calculations we use an initial states generated by the Effective String Rope model [1] for RHIC and LHC heavy ion reactions; which we also compare with results of the other models intending to calculate such initial states. [1] Magas, Csernai, Strottman, Phys. Rev. C 64 (2001) 014901; Nucl. Phys. A712 (2002) 167.

Speaker: Prof. Volodymyr Magas (University of Barcelona)

16:30 Observation of the charm baryon $\Lambda_{c}$ with ALICE at the LHC and perspectives for future measurements with the ALICE upgrade

ALICE is the LHC experiment dedicated to the study of the Quark-Gluon Plasma (QGP) in Pb-Pb collisions. Heavy quarks are very powerful probes to explore the QGP formation and its properties, since they are abundantly produced at LHC energies and they experience the entire evolution of the medium. The measurement of the $\Lambda_{c}$ yield relative to D mesons in Pb-Pb collisions would address the baryon over meson ratio in the heavy-quark sector. In pp and p-Pb collisions, the measurement of the $\Lambda_{c}$ production cross-section provides the necessary baseline to understand the results from heavy-ion collisions and improves the precision of the measurement of the total charm cross section. This baryon is observed with the present detector in pp and p-Pb collisions in the decay channel $\Lambda_{c}^{+} \rightarrow {\rm p K}^{-} \pi^{+}$. Given the small displacement of the $\Lambda_{c}$ secondary vertex from the interaction vertex ($\Lambda_{c}$ mean proper decay length c$\tau$ = 60 $\mu$m), the charm baryon is reconstructed using mainly kinematical selections and exploiting the ALICE particle identification capabilities. However, the observation of $\Lambda_{c}$ in Pb-Pb collisions is very challenging with the present detector, because of the large combinatorial background and because the mean proper decay length of the $\Lambda_{c}$ is smaller than the present vertex resolution for the $\Lambda_{c}$ decay, reconstructed from the three daughter tracks. An upgrade of the ALICE detector, including a new Inner Tracking System (ITS) is scheduled for the second long shutdown of the LHC. The new ALICE apparatus will provide improved resolution on the track impact parameter (by about a factor of 3) and will allow us to record data with higher rate. These new features will enable us to measure rare probes in Pb-Pb collisions, such as the $\Lambda_{c}$. Simulation studies, based on a detailed description of the new ITS, indicate that the measurements of the $\Lambda_{c}$ nuclear modification factor and azimuthal anisotropy will become possible with the integrated luminosity of 10 nb$^{-1}$, which is the target of the ALICE programme after the upgrade. We present the analysis strategy to observe the $\Lambda_{c}$ signal in various $p_{\rm T}$ intervals in pp collisions at $\sqrt{s}$ = 7 TeV and p-Pb collisions at $\sqrt{s}$ = 5.02 TeV, together with the perspectives for the measurements in Pb-Pb with the upgraded ITS.

Speaker: Rosa Romita (University of Liverpool (GB))

Slides PosterQM.pdf

16:30 On Chemical Freeze-outs of Strange and Nonstrange Hadrons

\noindent We performed a thorough analysis of two alternative approaches to treat the chemical freeze-out of strange particles in hadron resonance gas model with the multicomponent hard-core repulsion [1]. The first approach accounts for their chemical non-equilibrium via the usual $\gamma_s$ factor and such a model describes the hadron multiplicities measured in nucleus-nucleus collisions at AGS, SPS and RHIC energies with $\chi^2/dof = 63.4/55 \simeq$ 1.15. In contrast to earlier beliefs, we find that strangeness rather tends to be enhanced than suppressed at low collision energies, i.e. $\gamma_s > 1$, at $\sqrt{s_{NN}} = $ 2.7, 3.3, 3.8, 4.9, 6.3, 9.2 GeV. Second approach is to treat strange particle freeze-out separately from non-strange particle freeze-out. Conservation laws allow us to connect the freeze-outs of strange and non-strange hadrons and end up with the same number of free parameters as for $\gamma_s$ approach. We show that this approach works not worse than the $\gamma_s$ approach with $\chi^2/dof = 58.5/55 \simeq $ 1.06 and for $\sqrt{s_{NN}} = $ 6.3, 12 and 17 GeV it significantly improves the fit quality. For all considered collision energies we see that $\bar p/\pi^-$, $\bar \Lambda/\Lambda$, $\bar \Xi^-/\Xi^-$ and $\bar \Omega/\Omega$ ratios are described better than within the traditional $\gamma_s$ approach, since a separation of chemical freeze-outs relaxes the strong connection between the non-strange and strange baryons. The novel concept of strange particle freeze-out allows us to describe 111 independent hadron ratios measured at 14 different energies with the highest quality ever achieved. Basing on these results we conjecture that an apparent strangeness enhancement is due to the separate strangeness chemical freeze-out. \\ \noindent {\bf References:}\\ 1) K. A. Bugaev, D. R. Oliinychenko, J. Cleymans, A. I. Ivanytskyi, I. N. Mishustin, E. G. Nikonov and V. V. Sagun, Europhys. Lett. 104, 22002 (2013)

Speaker: Prof. Kyrill Bugaev (Bogolyubov Institute for Theoretical Physics of NAS of Ukraine, Kiev, Ukraine)

Slides QM2014_POSTER_338.pdf

16:30 On the pair correlations of neutral $K, D, B$ and $B_s$ mesons with close momenta produced in inclusive multiparticle processes

The comparative theoretical analysis of pair correlations of two neutral $K$ mesons and two neutral heavy mesons ( $D, B, B_s$ ), generated in inclusive processes -- hadron-hadron, hadron--nucleus and nucleus--nucleus collisions -- with strangeness and charm ( beauty ) conservation, is performed . For $K^0$ mesons, relations describing the dependence of the correlations of two short-lived and two long-lived neutral kaons and the correlations of "mixed" pairs $K^0_S K^0_L$ at small relative momenta upon the space-time parameters of the generation region of $K^0$ and $\bar{K}^0$ mesons have been obtained. It is shown that under the strangeness conservation the correlation functions of the pairs $K^0_S K^0_S$ and $K^0_L K^0_L$, produced in the same inclusive process, coincide, and the difference between the correlation functions of the pairs $K^0_S K^0_S$ and $K^0_S K^0_L$ is conditioned exclusively by the production of the pairs of non-identical neutral kaons $K^0 \bar{K}^0$. For the case of $D^0$, $B^0$ and $B_s^0$ mesons, correlations have the quite analogous character and they are described by quite similar expressions: in particular, just as for $K^0$ mesons, the correlation functions for the pairs of states with the same $CP$ parity ( $R_{SS}=R_{LL}$ ) and for the pairs of states with different $CP$ parity ( $R_{SL}$ ) do not coincide, and the difference between them is conditioned exclusively by the production of the pairs $D^0 \bar{D}^0, B^0 \bar{B}^0, B_s^0 \bar{B}_s^0$. However, contrary to the case of $K^0$ mesons, here the distinction of $CP$-even and $CP$-odd states encounters difficulties -- due to the insignificant differences of their lifetimes and the relatively small probability of purely $CP$-even and $CP$-odd decay channels, and one may hope that it will become possible at future colliders .

Speaker: Dr Valery Lyuboshitz (Joint Institute for Nuclear Research ( Dubna ))

Slides Quark_Matter_2014--Valery_Lyuboshitz_2.pdf

16:30 On the phase structure and dynamics of QCD

We discuss the phase structure of QCD at zero and non-vanishing temperature and density. The focus is on the deconfinement phase transition and, in particular, the thermodynamics of QCD close to criticality. The precise understanding of equilibrium physics allows to also compute temperature-dependent transport coefficients. For the ratio of shear viscosity over entropy we find a minimum close to but above the KSS bound at $T\approx 1.25\, T_c$, signalling almost perfect fluidity of the QGP as found in experiments at RHIC and LHC.

Speaker: Dr Leonard Fister (IPhT, CEA Saclay)

Poster Fister_QM_2014.pdf

16:30 p+Pb collisions at 5.02 TeV in the Parton-Hadron-String-Dynamics transport approach

The Parton-Hadron-String-Dynamics (PHSD) transport model is employed for p+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV and compared to recent experimental data from the LHC as well as to alternative models. We focus on the question of initial state dynamics, i.e. if the initial state might be approximated by a superposition of independent nucleon-nucleon collisions or should be considered as a coherent gluon field as predicted within the color glass condensate (CGC) framework. We find that the PHSD approach provides correlations between the charged particle multiplicity at midrapidity and the number of participant nucleons very close to results from the CGC and differs substantially from results calculated with Glauber initial conditions. However, a difference is found between the PHSD approach and CGC models with respect to the rapidity dependence of the average transverse momentum. Accordingly, related measurements at LHC should allow to prove or disprove the presence of coherent color fields in the initial phase of the collisions.

Speaker: Dr Volodymyr Konchakovski (Institute for Theoretical Physics, Giessen University)

16:30 Particle identification techniques for measuring the hadron composition in charged jets from pp collisions with the ALICE experiment

Jets provide experimental access to identify cascades of consecutive emission of partons from an initial hard QCD scattering. The process of parton showering and subsequent hadronisation is broadly known as fragmentation. Identified final state particles provide an enhanced sensitivity to the flavour dependence of fragmentation. The $\mbox{ALICE}$ detector at the LHC has excellent tracking and particle identification capabilities. In two independent analysis methods, we identify charged pions, kaons and (anti-)protons with transverse momenta from 150 MeV/$c$ up to about 40 GeV/$c$ using the specific energy loss (d$E$/d$x$) in the time projection chamber (TPC). We measure the hadron composition ($\pi$/K/p) in charged jets at mid-rapidity in pp collisions at $\sqrt{s} = 7$ TeV. Two independent techniques are utilised, the TPC Coherent Fit and the Multi-Template Fit. The details of these techniques will be discussed as well as a comparison of the results to the particle type dependence of inclusive charged hadron production.

Speaker: Benjamin Andreas Hess (Eberhard-Karls-Universitaet Tuebingen (DE))

Slides poster_v5.pdf

16:30 Parton energy loss in 3-jet events at RHIC and the LHC

We investigate the effect of parton energy loss on 3-jet events in high energy gold-gold and lead-lead collisions at RHIC and the LHC. We study the azimuthal angular distribution of the 3-jet events for various energy loss models and for different energy loss parameters. It is shown that 3-jet events have more discriminating power than single and double inclusive jets and are a more precise probe of parton energy loss dynamics in QGP.

Speaker: Prof. Jamal Jalilian-Marian (Baruch College)

16:30 Performance and study of B meson spectra in pp and pPb collisions in CMS

B meson reconstruction is of great interest in the heavy ion collisions. Measurement of B meson pseudorapidity and transverse momentum spectra can provide useful inputs for the study flavor dependence of jet quenching in PbPb collisions and for the determination of the heavy flavor nuclear parton distribution functions in pPb collisions. The performance of excusive B meson reconstruction with the CMS detector is reported. The B mesons are fully reconstructed with J/$\psi$ (via di-muon channel) and charged tracks. The background suppression techniques and analysis methods of B meson spectra are discussed in this poster.

Speaker: Gian Michele Innocenti (Massachusetts Inst. of Technology (US))

Slides PosterFINALGMI.pdf

16:30 Performance for the reconstruction of $\rm{\Lambda_b}$ baryons with the ALICE inner tracker upgrade

The ALICE detector is designed to investigate the properties of the hot and dense plasma of quarks and gluons, formed at the extreme energy densities reached in Pb-Pb collisions at the LHC. Heavy quarks are sensitive probes of this medium, because they are produced at the initial stage of the collision and they subsequently interact with the medium itself. In particular, an accurate measurement of heavy flavour production provides information on fundamental properties of the medium, like the transport coefficients and the thermalization and the hadronization mechanisms. Interesting results have been obtained in the first three years of data-taking at the LHC, but there are still open questions, which would require measurements beyond the present capabilities of the ALICE apparatus. Among the completely unexplored fields, the measurement of the production of the heavy flavour baryons, like $\rm{\Lambda_c}$ and $\rm{\Lambda_b}$, can bring insight on the heavy quark hadronization mechanism in the presence of a partonic medium. These measurements are not accessible in Pb-Pb collisions with the present ALICE apparatus and LHC luminosity. The ALICE upgrade planned for the second Long Shutdown in 2019 includes a new Inner Tracking System, with three times better tracking precision. In addition, a faster readout for most of the detectors will permit to fully exploit the increased Pb-Pb interaction rate of up to 50 kHz. In this poster we present the performance for the full reconstruction of the beauty baryon $\Lambda_b^{0} \rightarrow \Lambda_c^{+} + \pi^{-}$ decays (with $\Lambda_c^{+} \rightarrow {\rm p K}^{-} \pi^{+}$) in central Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.5 $\rm{TeV}$. The statistical significance of the measurement will be given for the target integrated luminosity of 10 nb$^{-1}$.

Speaker: Cristina Terrevoli (Universita e INFN (IT))

Slides QM2014_terrevoli_ITSup.pdf

16:30 Performance for the reconstruction of B mesons with the ALICE inner tracker upgrade

The installation of an upgraded Inner Tracking System (ITS) in the ALICE central barrel is planned during the second long shutdown of the LHC in 2019. The design of the new ITS presents 7 layers of silicon pixel detectors, starting from a radius of 2.24 cm from the beam line. The single hit resolution will be of about 4 $\mu$m and the material thickness will be as low as 0.3% of the radiation length for the three innermost layers. The readout rate capability of the ALICE central barrel of up to 50 kHz in Pb-Pb collisions will allow new and unique measurements in the heavy-quark sector. In this poster we focus on the performance of full kinematic reconstruction in the channel $\mathrm{B^{+}} \rightarrow {\rm \overline{D}^{0}} \pi^{+}$, and $\mathrm{\overline{D}^{0}} \rightarrow {\rm K^{+}} \pi^{-}$ with branching ratios of 0.5% and 3.9% respectively. The study was based on a detailed simulation of the new inner tracker and of the ALICE apparatus with Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.5 TeV. An outlook on the feasibility as well as an estimate on the physics performance will be presented.

Speaker: Johannes Hendrik Stiller (Ruprecht-Karls-Universitaet Heidelberg (DE))

Slides 2014-May-07-conferencefile-Johannes_Stiller_-_QM2014_Poster_-_ITS_Upgrade_v2.1(1).pdf

16:30 Performance Studies of b-jet identification in CMS

Jets associated with the production of bottom quarks in pp, ppb and PbPb collisions are identified by a variety of algorithms developed by CMS. These algorithms exploit the long lifetime and high mass of bottom quarks by using the impact parameters of charged-particle tracks, the properties of reconstructed decay vertices and the presence of a lepton or combinations of these quantities. In this poster, the performance of these algorithms including their efficiency and purity are discussed by the data measurements and their comparison with expectations based on simulations.

Speaker: Leo Yu (Rutgers, State Univ. of New Jersey (US))

Poster qm2014_draft6.pdf

16:30 Performance Studies of Inclusive jets in CMS

This poster presents the optimized techniques used to reconstruct inclusive jets in pp, pPb and PbPb collisions collected by the CMS detector. Jets are reconstructed using anti-$k_T$ sequential reconstruction algorithm on particle flow objects. Underlying event energy is estimated by various background subtraction techniques and their systematic uncertainties are studied. The events collected by high-$p_T$ jet triggers are combined to produce jet spectra in a large kinematic range and the corresponding trigger efficiencies are discussed. Various unfolding methods are employed to obtain the true jet distributions by utilizing Monte Carlo simulation samples.

Speaker: Raghav Kunnawalkam Elayavalli (Rutgers, State Univ. of New Jersey (US))

Poster Inclusive jet measurements in Heavy Ion collisions at CMS

16:30 Performance study for measurement of jets and heavy flavor using sPHENIX.

We will present our ongoing study of performance for measurement of jets and heavy flavors at the sPHENIX project using a Geant4 simulation. The sPHENIX is the planned/anticipated upgrade of the PHENIX detector at RHIC. The physics programs of sPHENIX primarily aim at jets and heavy flavors. The program can be much enhanced with the preshower and the EMCal that provides separation of single photons from double photons from neutral pions up to 40 GeV/c and improved electron identification. A possible design of the preshower and a possible design change of the EMCal has been studied using a Geant4 simulation. The preshower detector is a very thin sampling calorimeter which is hence capable to observe electromagnetic showers at their initial development. First we caluclate the lower limit of the opening angles of double photons from 40 GeV/c neutral pions. Setting the cell size less than the lower limit allows us to identify the double photons, hence to separate high pT single photons from high pT neutral pions. Second, we try to improve the rejection power against charged pions to get a clean electron sample. In other words, electron identification is another key performance goal. The rejection power is found to reach the order of a thousand by properly choosing the cut parameters on the energy and shower shape in the preshower and the EM calorimater.

Speaker: Mr Kazuya Nagashima (Hiroshima University)

Poster QM2014_poster_Kazuya_Nagashima.pdf

16:30 Perspectives of $\Upsilon$ production in ALICE and future prospects

The study of the production of bottomonium states and their suppression has been a proposed probe of the properties of the hot and dense medium created in high-energy heavy-ion collisions. In particular, some of the $\Upsilon$ states have a smaller size and larger binding energy than the J/$\psi$, and their study provides valuable information complementary to those obtained from charmonium. The $\Upsilon{\rm (1S)}$ state is expected to dissociate at a higher temperature than all the other quarkonium states, thus proving to be an effective thermometer of the system. This poster will highlight details of the $\Upsilon$ analysis in Pb-Pb collisions, along with future prospects of $\Upsilon$ studies in the ALICE experiment for the upcoming Run2 of the LHC.

Speaker: Dr Debasish Das (Saha Institute of Nuclear Physics (IN))

Slides poster_QM2014_ALICE_Upsilon_debasish_das.pdf

16:30 Phase diagram of lattice QCD in auxiliary filed Monte-Carlo method in the strong coupling region

We study the QCD phase diagram in the strong coupling region by using the auxiliary field Monte-Carlo method. Elucidating the phase diagram structure in QCD is a big challenge. The strong coupling lattice QCD is a promising machinery, in which the effective action is obtained by integrating the link variables analytically at a given order of the strong coupling expansion, then the sign problem is weakened. We have recently obtained the QCD phase diagram with fluctuation effects in the strong coupling limit by using the auxiliary field Monte-Carlo (AFMC) method [1]. Compared with the mean field results, hadron phase is found to be suppressed (extended) at low (high) chemical potential. These results are consistent with those obtained in the monomer-dimer-polymer (MDP) simulation [2]. It is staightforward to include finite coupling effects in AFMC. Next-to-leading order (NLO) effective action terms proportional to $1/g^2$ appear from one plaquette configurations and are found to contain four-Fermi and eight-Fermi interactions of quarks. Sequential extended Hubbard-Stratonovich transformations lead to an effective action in the bilinear form of quarks. Preliminary results seems to suggest that finite coupling effects make the sign problem more severe than in the strong coupling limit [3]. In the presentation, we also discuss the order of the phase transition based on the finite size scaling of the chiral susceptibility in the strong coupling limit. Several prescriptions to weaken the sign problem are also discussed. [1] T. Ichihara, A. Ohnishi, T. Z. Nakano, arXiv:1401.4647 [hep-lat]. [2] W. Unger, P. de Forcrand, J. Phys. G38 (2011) 124190. [3] T. Ichihara, A. Ohnishi, in preparation.

Speakers: Akira Ohnishi (Kyoto University), Mr Terukazu Ichihara (Kyoto University)

Poster QM2014-Ohnishi.pdf

16:30 Phase Structure of Strongly Interacting Matter: Thermodynamics and Chiral Anomaly

The thermodynamics of the finite temperature QCD crossover is investigated with a low-energy effective description. The resulting pressure and trace anomaly are in very good agreement with corresponding results from lattice Monte-Carlo simulations. Effects of the chiral anomaly on the phase structure are explored and results for the temperature dependence of the anomalously large mass of the $\eta'$-meson are presented.

Speaker: Mario Mitter (Univ. Heidelberg)

Poster poster_quarkmatter2014.pdf

16:30 PHENIX experimental search for the dark photon decay to di-electron pairs

A dark photon is a hypothetical particle which is very weakly coupled with ordinary photons in some Beyond the Standard Model (BSM) theories. The dark photon is a candidate for the annihilation of dark matter particles into $e^+e^-$ pairs, a process which could provide an explanation for the positron excess in the universe observed by several satellite experiments. It may also explain the $3\sigma$ discrepancy between the muon $g-2$ result and Standard Model calculations. The PHENIX experiment at RHIC has excellent capabilities for electron identification and for measuring $e^+e^-$ pairs with a very good mass resolution, making possible a search for such pairs from dark photon decay. We have conducted a search for possible $e^+e^-$ pairs from dark photons among a large data sample of pairs from $\pi^0$ Dalitz decays. We present new results of the dark photon search from the PHENIX experiment, which provide the world's best limits and rules out a majority of the mass-branching ratio region that could explain the $g-2$ result.

Speaker: Yorito Yamaguchi (University of Tokyo)

16:30 Photon production and elliptic flow in heavy-ion collisions within the PHSD approach

The QCD matter produced initially in ultra-relativistic nucleus-nucleus collisions is expected to represent a high temperature plasma, which should be evidenced in its electromagnetic radiation. We analyze the production of real and virtual photons from the strongly-coupled QGP in the initial stages of the collisions as well as the ('corona') radiation from the interacting mesons and baryons after hadronization using the parton-hadron-string dynamics (PHSD) transport model. The description of the bulk evolution in the microscopic PHSD approach is independently controlled by abundances, spectra and flow of final particles, which is found to be in agreement with experimental observation. In this contribution, we will provide a brief description of the relevant physics assumptions within the PHSD approach and give details on the implementation of the photon radiation in partonic and hadronic interactions and decays. Our calculations successfully describe the production of photons and dileptons in proton-proton as well as nucleus-nucleus collisions from SPS to RHIC and LHC energies. In particular, we find that the observed strong elliptic flow v_2 of direct photons can be understood theoretically only by a consistent modeling of both the 'early' partonic sources (q+q->g+gamma, q+g->q+gamma) and the 'late' hadronic interactions (mesons-meson and meson-baryon bremsstrahlung m+m->m+m+gamma, m+B->m+B+gamma) within the same approach.

Speaker: Dr Olena Linnyk (University of Giessen)

16:30 Pion femtoscopy measurements in small systems with ALICE at the LHC

The size of the particle emitting region at freeze-out obtained with femtoscopy is an important characteristic of heavy-ion collisions. Such a measurement for identical pions (sometimes called "HBT") provides a detailed picture of the system size and its dependence on pair transverse momentum and multiplicity. The A-A pion femtoscopy results are interpreted in the hydrodynamic framework as a signature of significant collective radial flow. The pp data could not be described in the same framework. It is of great interest how the p-A system would behave as compared to the pp and A-A results. In particular models based on hydrodynamics and calculations involving gluon saturation provide predictions for the system size in p-A collisions. A careful comparison of the radii measured in pp and p-A collisions is needed to verify those predictions. We present the pion femtoscopy results in p-Pb collisions at the LHC with ALICE. The analysis was performed in three dimensions using both standard Cartesian and Spherical Harmonics representations of the correlation function. The extracted femtoscopic radii are compared to the high multiplicity ALICE pp results as well as to model predictions.

Speaker: Lukasz Kamil Graczykowski (Warsaw University of Technology (PL))

Slides QM14_LGraczykowski_pPb_3DPionFemtoscopy_Poster.pdf

16:30 Pion-kaon femtoscopy in Au+Au collisions at $\sqrt{s_{NN}}$ = 39GeV at STAR

The main task of the Beam Energy Scan (BES) program at RHIC is to scan the QCD phase diagram with heavy-ion Au+Au collisions ( sqrt(s_NN) = 7.7 - 62.4GeV ) to find signatures for the 1st order phase transition and the critical point. Femtoscopy analysis allows us to extract information about size of the emission source. In particular, from the non-identical particles correlations, e.g. pion-kaon femtoscopy, one can obtain information about asymmetry in emission processes of pions and kaons. This asymmetry gives the knowledge of which type of particles is emitted first/second or/and from which area of the source. In this talk, we will present STAR data results of pion-kaon femtoscopy analysis at mid-rapidity in Au+Au collisions sqrt(s_NN) = 39GeV.

Speaker: Ms Katarzyna Poniatowska (Warsaw University of Technology)

Poster QM2014_Katarzyna_Poniatowska.pdf

16:30 Possible effect of mixed phase and deconfinement upon spin correlations in the $\Lambda \bar{\Lambda}$ pairs generated in relativistic heavy-ion collisions

Spin correlations for the $\Lambda \Lambda$ and $\Lambda \bar{\Lambda}$ pairs, generated in relativistic heavy ion collisions, and related angular correlations at the joint registration of hadronic decays of two hyperons, in which space parity is not conserved, are theoretically analyzed. The correlation tensor components can be derived from the double angular distribution of products of two decays by the method of "moments" . The properties of the "trace" of the correlation tensor ( a sum of three diagonal components ), determining the relative fractions of the triplet states and singlet state of respective pairs, are discussed. Spin correlations for two identical particles ($\Lambda \Lambda$) and two non-identical particles ($\Lambda \bar{\Lambda}$) are considered from the viewpoint of the conventional model of one-particle sources. In the framework of this model, correlations vanish at sufficiently large relative momenta. However, under these conditions -- especially at ultrarelativistic energies -- in the case of two non-identical particles (Lambda--anti-Lambda) a noticeable role is played by two-particle annihilation ( two-quark, i.e. quark-antiquark, and two-gluon ) sources, which lead to the difference of the correlation tensor from zero. In particular, such a situation may arise, when the system passes through the "mixed phase" and -- due to the appearance of free quarks and gluons in the process of deconfinement of hadronic matter -- the number of two-particle sources strongly increases .

Speaker: Dr Valery Lyuboshitz (Joint Institute for Nuclear Research, Dubna)

Slides Quark_Matter_2014--Valery_Lyuboshitz_1.pdf

16:30 Possible resolution of the early thermalization problem in relativistic heavy-ion collisions: decoherence entropy from the Glasma

The entropy production in the initial stage of relativistic heavy-ion collision is studied based on the classical Yang-Mills dynamics in the non-expanding plasma by constructing the corresponding (quantum) coherent state. The decoherence entropy is calculated from the distribution of the gluon occupation number given by the coherent state. We find that the importance of the fluctuations in the longitudinal direction in the initial glasma state for the onset time of the chaotic behavior and hence the entropy production; the larger the fluctuations, the fater the thermalization. We show that reasonable strengths of the initial fluctuations with respect to the amplitude of the background classical field could account for the early thermalization suggested by the phenomenological analysis based on the hydrodynamics, provided that the decoherence time is obtained.

Speaker: Hideaki Iida (Kyoto University)

Poster QM2014_iida_2.pdf

16:30 Probe the QCD media using $\phi$-meson event anisotropy $v_{2}$

One of the major goals of the heavy-ion experiments is to study the properties of hot and dense matter created in the collision of two heavy nuclei. Elliptic flow ($v_{2}$) of $\phi$ meson in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV has provided a clear evidence for partonic collectivity[1]. This was possible because of the small hadronic interaction cross section and early freeze-out for $\phi$ mesons[2]. On the other hand hadrons like protons (with similar mass as $\phi$ meson) have significantly large hadronic interaction cross section and freeze-out late. Therefore, comparison between $v_{2}$ of $\phi$ meson and proton will be useful to understand the dynamical evolution of the hot and dense media created in such collisions. In order to study the QCD phase structure, RHIC has conducted the beam energy scan program since 2010. In this talk, we report the measurement of $p_{T}$ integrated $v_{2}$ of $\phi$ mesons as a function of center of mass energy from 7.7 GeV to 200 GeV to demonstrate the decrease in partonic contribution to collectivity with the decrease in $\sqrt{s_{NN}}$. We compare the $\phi$-meson $v_{2}$ to the corresponding values for protons. At high collision energies, $\sqrt{s_{NN}}$ $>$ 27 GeV for example, we observe similar values for the integrated $v_{2}$ for both protons and $\phi$ meson. At lower energies, $\sqrt{s_{NN}}$ $<$ 19.6 GeV, however, $\phi$-meson $v_{2}$ become much smaller, indicating that hadronic interactions become dominant in the energy region. Further we compare to transport model calculations with and without partonic interactions to emphasize our conclusions. In addition, the effect of hadronic re-scattering on $v_{2}(p_{T})$ will be shown by comparing $v_{2}(p_{T})$ of $\phi$ and proton. The study of re-scattering effect on $v_{2}$ will be further corroborated by using various models like those based on Hydro+Cascade and Transport approach. References [1] B. I. Abelev $\it$ et al. (STAR Collaboration), Phys. Rev. Lett. $\textbf{99}$, 112301 (2007). [2] A. Shor, Phys. Rev. Lett. $\textbf{54}$, 1122 (1985); J. Adams $\it$ et al. (STAR Collaboration), Nucl. Phys. $\textbf{A 757}$, 102 (2005); Md. Nasim, B. Mohanty and N. Xu, Phys. Rev. $\textbf{C 87}$, 014903 (2013).

Speaker: Mr Md Nasim (NISER, Bhubaneswar, India)

Slides QM_poster_nasim.pdf

16:30 Probing the collective confining colour field by direct photons and lepton pairs

Intensive radiation of magnetic bremsstrahlung type (synchrotron radiation) resulting from the interaction of escaping quarks with the collective confining colour field is suggested as new possible mechanism of experimentally observed direct photon anisotropy. The polarization properties of such photons and the pecularities in the angular asymmetry of radiated lepton pairs related to the mechanism proposed are also discussed.

Speaker: Prof. Gennady Zinovjev (National Academy of Sciences of Ukraine (UA))

16:30 Production of Phi mesons in pPb and PbPb collisions in CMS

The phi meson is a versatile probe for studying the hot medium created in heavy ion collisions. Its low hadronic interaction cross section can provide important insights into the early time dynamics of the collective expanding medium. In this analysis, the performance of phi meson reconstruction via the decay channel of K+K- is presented for high multiplicity events in 5.02 TeV pPb and 2.76 TeV PbPb collisions using the CMS detector. The yield of phi mesons is extracted in the transverse momentum range of 2-20 GeV/c. Technique of extracting second-order anisotropy harmonics (v$_2$) of phi mesons from long-range two-particle correlations will also be discussed.

Speaker: Mukund Madhav Varma (Massachusetts Inst. of Technology (US))

16:30 Projection method and new formulation of leading-order anisotropic hydrodynamics

Successful applications of relativistic viscous hydrodynamics in the description of heavy-ion collisions at RHIC and the LHC triggered large interest in the development of the hydrodynamic framework. An example of the new approach to relativistic dissipative hydrodynamics is anisotropic hydrodynamics --- the framework where effects connected with the expected high pressure anisotropy of the produced matter are included in the leading order of the hydrodynamic expansion. Very recently, also the second order anisotropic hydrodynamics has been formulated in [1]. The new approach introduced in [1] allows for description of arbitrary transverse expansion of matter in the way which becomes consistent with more traditional approaches to dissipative hydrodynamics in the small anisotropy limit. This formalism uses, however, the Romatschke-Strickland form [2] of the distribution function in the leading order, which implies that the two components of pressure in the transverse plane may be different only if the second-order corrections are taken into account. In this work we present a new methodology for including three substantially different pressure components already in the leading order of hydrodynamic expansion. Our approach is based on the projection method introduced in [3], which has turned out to be a convenient tool to replace complicated tensor equations of relativistic hydrodynamics by a small set of scalar equations. We take into account the radial expansion of the produced matter (in addition to the longitudinal Bjorken flow) but our considerations are confined to the case with cylindrical symmetry. We generalize the Romatschke-Strickland form to the case where all three pressure components may be different. Compared to earlier works on anisotropic hydrodynamics in the leading order, where the zeroth and first moments of the Boltzmann equation have been studied, an important novel feature of our present work is the analysis of the second moment of the Boltzmann equation. We argue that a successful agreement with the Israel-Stewart theory in the limit of small anisotropies may be achieved if we take into account two equations constructed from the second moment of the Boltzmann equation rather than taking one equation from the zeroth moment and another equation from the second moment [4]. [1] D. Bazow, U. Heinz, and M. Strickland, arXiv:1311.6720. [2] P.Romatschke and M.Strickland, Phys. Rev. D68 (2003) 036004. [3] W. Florkowski and R. Ryblewski, Phys. Rev. C85 (2012) 044902. [4] L. Tinti, W. Florkowski, arXiv:1312.6614.

Speaker: Dr Leonardo Tinti (UJK)

Poster QM2014.pdf

16:30 Properties of neutral pions in a hot and magnetized quark matter

The study of quark matter at extreme temperature and in the presence of very strong magnetic fields has attracted much attention over the past few years. There are evidences for the creation of very strong and short-living magnetic fields in the early stages of noncentral heavy ion collisions at RHIC and LHC. Depending on the collision energies and impact parameters, they are estimated to be of order $eB\sim 1.5 m_{\pi}^{2}$ at RHIC and $eB\sim 15 m_{\pi}^{2}$ at LHC. In this talk, we will focus on the effect of constant magnetic fields on the properties of neutral mesons in a hot and dense quark matter. In particular, we will explore the temperature (T) dependence of neutral pion masses as well as their refraction indices for various fixed magnetic fields (eB). Moreover, using the generalized PCAC relations for hot and magnetized pions, we will derive the low energy Goldberger-Treiman (GT) and Gell--Mann-Oakes-Renner (GOR) theorems for neutral pions at finite T and eB. To do this, we will mainly use the energy dispersion relation of neutral pions, including nontrivial form factors. It will be derived from the effective action of a two-flavor Nambu--Jona-Lasinio model in a derivative expansion up to second order. We will show that the refraction index of neutral pions exhibits certain anisotropy in the transverse and longitudinal directions with respect to the direction of the external magnetic field. Moreover, as it turns out, the transverse refraction indices are, in contrast to their longitudinal refraction indices, larger than unity. These results are consistent with generalized low energy GT and GOR theorems for neutral pions at finite T and eB.

Speaker: Prof. Neda Sadooghi (Department of Physics, Sharif University of Technology, Tehran, Iran)

Poster Sadooghi-QM2014-2.pdf

16:30 Prospects for beauty-jet measurements with ALICE

Heavy quarks, i.e. charm and beauty, are ideal probes of the QCD matter formed in relativistic heavy-ion collisions, as they are predominantly produced in the early stage of the collision via initial hard parton scatterings. While propagating through the dense matter, they lose energy through elastic scatterings and radiative processes. Theoretical models predict that the energy loss of high-energy partons depends on the color charge and parton mass, with the expectation that in the medium beauty quarks lose less energy than charm and light quarks. These dependencies can be explored by comparing the modification in Pb-Pb collisions, relative to pp collisions, of beauty jets with that of charm or light-parton jets. In this poster we present Monte Carlo based performance studies of different b-jet tagging algorithms in ALICE for pp collisions at $\sqrt{s}$ = 7 TeV. The algorithms, which benefit from the long lifetime of B mesons, are based on the identification of secondary decay vertices and displaced single tracks. In addition, the identification of electrons in jets can be used to profit from the large semi-electronic decay branching ratios of B mesons. Their capability to discriminate beauty jets from charm and light-parton jets will be discussed along with the analysis strategy and outlook. The performance after the ALICE upgrade, which foresees a new Inner Tracking System with improved spatial resolution, will also be presented.

Speaker: Sarah La Pointe (Universita e INFN (IT))

Slides QM14-bjet-poster-final.pdf

16:30 Prospects for measuring heavy-flavour hadron decay electron - jet correlations with the ALICE detector

The ALICE Collaboration measured a significant suppression of the production of high transverse momentum ($p_{\rm T}$) electrons from heavy-flavour hadron decays at central rapidity in Pb-Pb collisions with respect to proton-proton collisions. This indicates that charm and beauty quarks interact significantly, losing energy, with the Quark Gluon Plasma (QGP) formed in heavy-ion collisions. The study of azimuthal correlations between electrons from heavy-flavour hadron decays and jets opens the possibility to measure the properties of jets coming from heavy-quark fragmentation, complementing the information on the energy-loss mechanism provided by single-particle observables. In particular, the request of a high $p_{\rm T}$ 'trigger' electron can select preferentially electrons and jets deriving from quark pairs produced at the surface of the QGP fireball, allowing us to study in more detail the dependence of the energy loss on the path length travelled by the quark in the medium. Furthermore, by varying the jet radius, the angular distribution of the radiated energy can be investigated. Besides providing a reference for the Pb-Pb case, the analogous study in pp and p-Pb collisions can supplement the measurements of $p_{\rm T}$-differential cross sections of charm and beauty particles with angular-differential information, adding sensitivity to the different heavy-flavour production processes (e.g. pair production vs. gluon splitting). The analysis status and the prospect for such measurements in pp, p-Pb and Pb-Pb collisions with the ALICE detector will be discussed.

Speaker: Andrea Rossi (CERN)

Slides PosterEleJetRossiQM2014.pdf

16:30 Prospects for the ALICE muon physics with the Muon Forward Tracker upgrade

During the second long shutdown of the LHC in 2019 the ALICE detector will be improved with the installation of a new Muon Forward Tracker (MFT). This detector will crucially contribute to the precise characterization of the high-temperature, strongly-interacting medium created in ultra-relativistic Pb-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.5$ TeV. Covering the pseudo-rapidity range $2.5 < \eta < 3.6$, the MFT will be composed of six silicon pixel planes added in the acceptance of the existing Muon Spectrometer, upstream to the hadron absorber. Detailed results on the expected physics performances of MFT will be given in central Pb–Pb collisions for various benchmark analyses, assuming an integrated luminosity of $10~\mathrm{nb^{-1}}$ as expected for the LHC Run 3 (2020-2022). For the heavy-flavor physics, the focus is given on the measurement of open charm and beauty production (single muons from charm and beauty mesons and displaced J/$\psi$ production from b down to zero $p_\mathrm{T}$), as well as on the performances on the $\psi'$ measurement down to zero $p_\mathrm{T}$. Expected physics performances will be also shown for the measurement of low and intermediate mass dimuons, allowing the study of light neutral meson production and the thermal radiation from the QGP.

Speaker: Antonio Uras (Universite Claude Bernard-Lyon I (FR))

16:30 Prospects of effective Polyakov line actions for investigations of dense nuclear matter

Numerical simulations of QCD on the lattice is an essential tool for non-perturbative investigations at finite temperature. At finite density these investigations are hampered by the sign problem. A reformulation in terms of a Polyakov effective theory allows to circumvent this problem to a large extend. I will summarize the derivation of the effective action in terms of a spatial strong coupling expansion and discuss applications, in particular in the region of dense nuclear matter.

Speaker: Georg Bergner

Poster poster.pdf

16:30 Pseudo-rapidity dependence of inclusive photon multiplicity distribution at forward rapidity in STAR at RHIC Beam Energy Scan energies

The STAR experiment at Relativistic Heavy Ion Collider (RHIC) has been studying the properties of the QCD matter at extremely high energy density and parton density, created in the heavy ion collisions. Photons are produced at all stages of the colliding system directly as well as through decay of produced particles like neutral pions. The multiplicity and pseudo-rapidity distribution of photons on an event-by-event basis is an important measurement complementing the charged particle measurement in a heavy ion collision. The Photon Multiplicity Detector in the STAR experiment measures inclusive photons in the pseudo-rapidity region −3.7 < η < −2.3. The photon multiplicity per participating nucleon pair was observed to be independent of collision centrality for Au + Au collision at √sNN = 200 and 62.4 GeV indicating that photon production is dominated by soft processes [1, 2]. Inclusive photon production at forward rapidity also shows an energy-independent longitudinal scaling at these energies [1, 2]. We will present the multiplicity and pseudo-rapidity distributions of photons in Au+Au collisions at √sNN = 39, 27 and 19.6 GeV for different event centralities at rapidity close to the beam rapidity to further test the energy and centrality dependence of the longitudinal scaling. Photon multiplicity as well as pseudo-rapidity distributions show more photons as compared to that expected from longitudinal scaling; the deviation increasing for peripheral collisions. We assume that these additional photons from excited spectators due to proximity of PMD to beam rapidity. We propose a simple parameterization to calculate the effective number of photon sources, N’, to include contribution from participants as well as spectators, at all three energies. The photon multiplicity when scaled with N’ exhibits longitudinal scaling even beyond the beam rapidity. References [1] STAR Collaboration, Phys.Rev. C73 034906 (2006) [2] STAR Collaboration, Nucl.Phys. A 832 134-147 (2010)

Speaker: Rashmi Raniwala (University of Rajasthan (IN))

16:30 QCD effective potential with strong electromagnetic fields at zero and finite temperatures

Motivated by the observation that non-central heavy-ion collisions in RHIC and LHC are accompanied by extremely strong magnetic fields, much attention has been paid to the QCD dynamics in strong electromagnetic fields. In particular, the change of vacuum properties such as quark condensates has been investigated in terms of both effective models and lattice simulations. While both of these approaches predict, at zero temperature, an enhancement of quark condensates in the presence of magnetic fields (called "magnetic catalysis"), their results do not coincide with each other at finite temperatures. Namely, at finite temperatures, lattice QCD simulations at physical point predict "inverse" magnetic catalysis which is never reproduced by effective models. In order to bridge the gap between effective models and lattice QCD, an analytic study of QCD in the presence of strong magnetic fields should be necessary. As a first step towards understanding the effects of magnetic fields on QCD vacuum properties, we analytically investigate the QCD effective potential within one loops of gluon and quark including all order interactions with chromo-electromagnetic fields and $U(1)_{em}$ electromagnetic fields at zero and finite temperatures. First, we will show the results of QCD effective potential with strong magnetic fields at zero temperature [1]. The resulting effective potential is renormalization-group invariant. We found that the chromo-magnetic field prefers to be parallel to the external magnetic field, and thus the QCD vacuum with strong magnetic fields is spatially anisotropic. This result is consistent with recent lattice data [2,3]. Furthermore, the chromo-magnetic condensate increases with an increasing magnetic field, which supports the "gluonic magnetic catalysis" as observed in current lattice data [2]. Next, we will discuss the effective potential with strong electromagnetic fields at finite temperatures [4]. In particular, we focus on the influence of electromagnetic fields on the center symmetry in QCD. The pure Yang-Mills theory has the center symmetry (being spontaneously broken at high temperature), but dynamical quarks explicitly break it. We will show how the electric and magnetic fields affect the explicit symmetry breaking, by using the effective potential for the Polyakov loop. We will also discuss a relation between the property of the Polyakov loop in the presence of magnetic fields and the inverse magnetic catalysis, whose importance is pointed out from the recent lattice study [5]. References: [1] S. Ozaki, arXiv:1311.3137 (to be published in Phys. Rev. D) [2] G. S. Bali et al., JHEP 1304, 130 (2013) [3] E. -M. Ilgenfritz et al., Phys. Rev. D85, 114504(2012) [4] S. Ozaki, K. Hattori and K. Itakura, in preparation [5] F. Bruckmann et al., JHEP 1304, 112 (2013)

Speaker: Dr Sho Ozaki (KEK)

Poster quark_matter_postor_2014_ozaki.pdf

16:30 QCD Phase Diagram from the Lattice at Strong Coupling: Staggered vs. Wilson Fermions.

We compare two different approaches to strong coupling lattice QCD which are suited to study the phase diagram in the $\mu-T$ plane: The first is based on staggered fermions, the second is based on Wilson fermions. Since in both formulations the gauge links are integrated out analytically, the sign problem is much milder than in conventional lattice QCD. The resulting dual representation in terms of color singlets allows to better understand the nature of nuclear interactions. Since both fermion discretizations have different lattice artifacts, a comparison is instructive to isolate the physical content which persists as one aims for the continuum limit, in particular the existence of the critical end point. The strong coupling limit of staggered fermions is well established, recent results on the corresponding $\mu-T$ phase diagram and its corrections to the strong coupling limit are presented. For Wilson fermions, no such results have been obtained yet for QCD, only the Schwinger model has been addressed so far. We present the status and prospects to extend this approach to SU(3) in four dimensions.

Speaker: Wolfgang Unger (U)

Slides posterQM14.pdf

16:30 QCD-like theories at finite density

QCD suffers from a sign problem which hampers Lattice Monte Carlo simulations at finite chemical potential. One way to circumvent this problem in order to gain insights into the phase diagram of strongly interacting matter at finite density is to consider QCD-like theories where this problem is absent. In this talk we will discuss the phase diagrams of two prototypical examples, 2-color QCD [1,2] and QCD with isospin chemical potential [3], along with their implications for the phase diagram of 3-color QCD at finite density and relations to other strongly interacting systems such as ultracold Fermi gases with a population imbalance. [1] Phys.Rev. D85 (2012) 074007 [2] arXiv:1306.2897 [hep-ph] [3] Phys.Lett. B718 (2013) 1044-1053

Speaker: Dr Nils Strodthoff (Universitaet Heidelberg)

16:30 QGP formation time and the elliptic flow of direct photons

In this talk we investigate the information carried by the large elliptic flow of direct photons, observed at RHIC and LHC, in the frame work of (3+1)-dimensional ideal hydrodynamical model constrained with hadronic data. It is found that the transverse momentum spectra of direct photons can be explained much more easily, while a good explanation of the observed elliptic flow of direct photons can only be reached if the two time scales, thermal and chemical equilibrium are chosen properly, ie, about $1/3$~fm/c and 2~fm/c, respectively. The realization of thermal and chemical equilibrium are hot questions in relativistic heavy ion physics. The elliptic flow of direct photon serves as a more strict clock to those questions than other observables. High order harmonics of direct photons from PbPb collisions at 2.76~TeV are also predicted based on event-by-event fluctuation in this work, which look very similar to those of hadrons.

Speaker: Mrs Fu-Ming LIU (CCNU, Wuhan)

Poster QM2014poster.pdf

16:30 QGP parameter extraction via a global analysis of event-by-event flow coefficient distributions

A primary goal of heavy-ion physics is the measurement of the fundamental properties of the quark-gluon plasma (QGP), notably its transport coefficients, such as the specific shear viscosity $\eta/s$. Since these properties are not directly measurable, one relies on a comparison of the data to computational models of the time-evolution of the collision to connect measured observables to the properties of the transient QGP state. The computational model parameters are tuned such that simulated observables optimally match experimental data. Most studies to date are severely limited by computation time: they typically rely on averaged quantities such as the average elliptic flow coefficient $\langle v_2 \rangle$ for a given centrality bin -- disregarding the effects of event-by-event fluctuations -- and use ad hoc methods for optimizing model parameters. Often, each parameter is varied independently, while best-fit values are chosen via qualitative comparisons to single observables. This neglects correlations among parameters and leads to nebulous results lacking quantitative uncertainty. We propose a systematic model-to-data comparison method for extracting QGP properties. First, a set of salient model parameters is chosen for calibration -- physical properties such as transport coefficients are of primary interest. An event-by-event model is then evaluated at many points in parameter space; this is made possible by recent advances in high-throughput computing. Finally, a statistical surrogate algorithm is used to interpolate the parameter space and determine the values which optimally reproduce experimental data. This provides rigorous constraints including quantitative uncertainty and sheds light on the relative importance of each parameter. The methodology is applied to a modern hybrid model with MC-Glauber and MC-KLN initial conditions, viscous 2+1D hydrodynamics, and the hadron cascade UrQMD. By leveraging the power of the Open Science Grid, we have run event-by-event simulations over wide ranges of several crucial parameters, e.g. the shear viscosity and hydrodynamic thermalization time. We calibrate the model to experimental event-by-event flow distributions measured by the ATLAS experiment; these distributions are sensitive to initial-state fluctuations and therefore constitute a more comprehensive probe of the QGP than event-averaged flow. This massive-scale model-to-comparison yields new constraints on fundamental QGP properties and clarifies the essential features of a physically accurate model. The method is general and easily extensible to future studies.

Speaker: Mr Jonah E. Bernhard (Duke University)

Poster Bernhard, Jonah - poster

16:30 Quantifying the applicability of the fluid dynamical description of AA and pA collisions using Knudsen numbers

We investigate the applicability of fluid dynamics in ultrarelativistic heavy ion (AA) collisions and high multiplicity proton nucleus (pA) collisions. In order for fluid dynamics to be applicable the microscopic and macroscopic scales of the system have to be sufficiently separated. The degree of separation can be quantified by the ratio between these scales, usually refered as the Knudsen number. In this work, we calculate the Knudsen numbers reached in fluid dynamical simulations of AA and pA collisions at RHIC and LHC energies. For this purpose, we consider different choices of shear viscosity parameterizations, initial states and initialization times. We then estimate the values of shear viscosity for which the fluid dynamical description of ultrarelativsitic AA and pA collisions breaks down. In particular, we calculate how such values depend on the initial condition and system size. We found that the maximum shear viscosity allowed in AA collisions is of the order $\eta/s \sim 0.1 - 0.2$, which is similar in magnitude to the viscosities currently employed in simulations of heavy ion collisions. For pA collisions, we found that such limit is significantly lower, being less than $\eta/s=0.08$.

Speakers: Gabriel Denicol (McGill University), Harri Niemi (University of Jyväskylä)

Poster qm14poster.pdf

16:30 Quark Ensembles with Infinite Correlation Length

Exactly integrable (in the Luttinger’s sense) quark models of quantum field theory with infinite correlation length are considered. We calculate the form of energy distribution and find out such a form results in an instability of standard vacuum quark ensemble---Dirac sea. Then the corresponding momentum distribution becomes infinitely narrow with momentum cutoff going to infinity and leads to large (unlimited) fluctuations. The comparative analysis of various vacuum ensembles - the Dirac sea, neutral ensemble and the BCS superconductor state is made. We make a clear choice in favor of the BCS state as the ground state of quark ensemble with color interaction.

Speaker: Prof. Gennady Zinovjev (National Academy of Sciences of Ukraine (UA))

16:30 Quark production, Bose-Einstein condensates and thermalization of the quark-gluon plasma

In this talk, I would like to report the results of our recent work on the thermalization of gluons and $N_f$ flavors of massless quarks and antiquarks in a spatially homogeneous system. First, we give two coupled transport equations for gluons and quarks (and antiquarks), which are derived within the diffusion approximation of the Boltzmann equation with only $2\leftrightarrow 2$ processes included in the collision term. These transport equations are solved numerically in order to study the thermalization of the quark-gluon plasma. Next, we discuss three different patterns of the thermalization of the quark-gluon system. At initial time, we assume that no quarks or antiquarks are present and we choose the gluon distribution in the form $f = f_0~\theta\left(1-\frac{p}{Q_s} \right) $ with $Q_s$ the saturation momentum and $f_0$ a constant. The subsequent evolution of systems may, or may not, lead to the formation of a (transient) Bose condensate, depending on the value of $f_0$. The three patterns of thermalization are as follows: (a) thermalization without gluon Bose-Einstein condensates (BEC) for $f_0\leq f_{0t}$, (b) thermalization with transient BEC for $f_{0t} < f_0 \leq f_{0c}$ and (c) thermalization with BEC for $f_{0c} < f_0 $. Here, the values of $f_{0t} $ and $f_{0c} $ depend on $N_f$. When $f_0 \geq 1 > f_{0c}$, the formation of BEC starts at a finite time $t_c\sim\frac{1}{(\alpha_s f_0)^2}\frac{1}{Q_s}$. We also find that the equilibration time for $N_f = 3$ is typically about 5 to 6 times longer than that for $N_f = 0$ at the same $Q_s$.

Speaker: Dr Li Yan (IPhT Saclay)

16:30 Quark-gluon plasma connected to finite heat bath

We present the derived entropy formulas for finite reservoir systems, S(q), from universal thermostat independence and obtain the functional form of the corresponding generalized entropy-probability relation [1]. Our result interprets thermodynamically the subsystem temperature, T(1), and the index q in terms of the temperature, T , entropy, S , and heat capacity, C of the reservoir as and . In the infinite C limit, irrespective of the value of S , the Boltzmann-Gibbs approach is fully recovered. We apply this framework for the experimental determination of the original temperature of a finite thermostat, T , from the analysis of hadron spectra produced in high-energy collisions, by analyzing frequently considered simple models of the quark-gluon plasma. [1] T.S. Biró, G.G. Barnaföldi, P. Van: Eur.Phys.J. A49 (2013) 110

Speaker: Gergely Barnafoldi (Hungarian Academy of Sciences (HU))

Poster BarnaföldiGG_QM2014_v1.pdf

16:30 Quark-hadron phase transition in the PNJL model with hadronic excitations

We study the QCD phase transition, especially the change of degrees of freedom from hadrons to quarks. In order to describe the chiral phase transition and the deconfinement transition at the same time, we choose the Nambu-Jana-Lasinio model with Polyakov loop (PNJL model). This model was proposed by combining the Nambu-Jana-Lasinio model which describes the chiral transition and the Polyakov loop which works as an order parameter of deconfinement transition. We calculated an equation of state by an approach beyond the mean field approximation to take thermal excitations of hadrons into account. In this method, mesons can be introduced as auxiliary fields, and their excitations are described as thermal fluctuations of auxiliary fields. We will present an equation of state concerning mesonic excitations at zero quark chemical potential in the two- and three-flavor PNJL model for interacting quarks [1, 2]. In addition, we have thought the way to introduce baryonic correlation as the three body system of quarks at finite chemical potential. In this case, it is necessary to consider how to put interactions between three quarks, unlike mesons as the two body system of quark and anti-quark. We will also discuss about that. [1] K. Yamazaki and T. Matsui, Nucl. Phys. A 913 (2013) 19. [2] K. Yamazaki and T. Matsui, Nucl. Phys. A 922 (2014) 237.

Speaker: Kanako Yamazaki (University of Tokyo)

Poster yamazaki.pdf

16:30 Quarkonia production in p$+$p collisions from the STAR experiment

Quarkonium production in heavy-ion collisions is an important tool for studying the properties of quark-gluon-plasma (QGP). Interpretation of these results requires a good understanding of the production mechanisms in p$+$p collisions, which include direct production via gluon fusion, parton fragmentation, and feed down from higher quarkonium states. Despite decades of efforts, the quarkonium production mechanism still remains an open question to date. New quarkonium measurements, especially production at high tranverse momentum and spin alignment for various beam energies, are necessary to constrain models. In this presentation we report on the new measurements of $J/\psi$ and $\psi(2S)$ invariant yields in a broad range of transverse momentum ( $4 < p_{T} < 20 GeV/c$ )at midrapidity ($|y| < 1.0$) in p$+$p collisions at $\sqrt{s} =$ 500 GeV from STAR. We further present the new polarization measurements from $J/\psi$ and $\Upsilon$ in p$+$p collisions at $\sqrt{s}$ = 200 GeV and 500 GeV from STAR. Comparisons among model calculations will be discussed.

Speaker: Qian Yang (U)

Poster QM14poster_QianYang.pdf

16:30 Quartetting in fermion systems with differing chemical potentials

In the ongoing effort to map the QCD phase diagram, the region of low temperature and moderately high density is particularly challenging for theorists. The phase structure in that region is determined by competition between Cooper pairing (driven by attractive strong interactions) and the strange quark mass (which is a source of flavor asymmetry, separating the Fermi momenta of the three quark flavors). There are various proposed outcomes of this competition, including crystalline ("LOFF") condensates and deformed Fermi surfaces. We argue that a condensate of Cooper quartets rather than pairs is a strong candidate for the ground state. The quartet is favored by the same QCD attraction that drives Cooper pairing, but with four quarks rather than two it is easier to construct a translationally invariant condensate that includes different flavors without paying an energy penalty due to the flavor asymmetry. This concept is also applicable to other systems of fermions with flavor asymmetry, including ultracold atoms and nuclear matter.

Speaker: Andreas Windisch (University of Graz)

Poster darmstadt_aw.pdf

16:30 RAA and v2 of muons from heavy flavour decays at forward rapidities at 2.76 ATeV

Heavy quarks produced in the initial stage of heavy ion collisions would traverse the quark gluon plasma. While traversing the quark gluon plasma, they will loose energy by colliding with quarks and gluons and also by radiating gluons. After their production, they may get fragmented into heavy mesons by picking up light quarks/antiquarks and in turn may decay through leptonic channels. These leptons would carry information of the initial stage of heavy ion collisions and also the evolution of the plasma. In this work, we have made a detailed study for the nuclear modification factor, RAA and elliptic flow, v2 of muons from heavy flavours decay at forward rapidities in Pb+Pb collision @ 2.76 ATeV at LHC. The pT distribution of heavy quarks produced from the initial fusion of partons, is obtained from FONLL ( Fixed Order Next-to-Leading Logarithms) approach [3, 4]. We consider both the radiative and collision energy loss along with a boost-invariant expansion of the plasma for the prediction of RAA as well as v2. The fragmentation of heavy quarks into D-mesons is governed by Peterson fragmentation function [5]. We compare our result of muon RAA from heavy flavour in Pb+Pb collisions at 2.76 ATeV with the ALICE data and found that our result can satisfactorily explain the experimental data. The nuclear modification factor of muons at 0-10% centrality calculated by the present formalism [2] has shown very good agreement with the ALICE data [6]. However the calculation shows more suppression while we take account the collisional energy loss. We also compare our result of muon v2 from heavy flavour at 20-40% centrality for Pb+Pb collisions at 2.76 ATeV with the ALICE Preliminary data [7]. References: 1. U. Jamil and D. K. Srivastava, J. Phys. G 37, 085106 (2010). 2. R. Abir et al., Phys. Lett. B 715, 183 (2012). 3. M. Cacciari, M. Greco and P. Nason, J. High Energy Phys.9805, 007 (1998). 4. M. Cacciari, S. Frixione and P. Nason, J. High Energy Phys.0103, 006 (2001). 5. C. Peterson, D. Schlatter, I. Schmitt, P. Zerwas, Phys. Rev. D 27, 105 (1983). 6. ALICE Collaboration, Phys. Rev. Lett. 109, 112301 (2012). 7. Xiaoming Zhang for the ALICE Collaboration, LBNL, USA, Strangeness in Quark Matter, 22-27 July, 2013, Bermingham, U.K.

Speaker: Dr Umme Jamil Begum (Debraj Roy College, Golaghat, Assam, India)

16:30 Rapidity gap events in proton-proton and ultra-peripheral heavy ion collisions at RHIC and the LHC

We study diffraction in proton-proton and ultra-peripheral heavy ion collisions at RHIC and the LHC using a gluon saturation-based model. The building blocks of the model are gluon ladders, singlet states of two-Reggeized gluons which satisfy the BFKL evolution equation, as well as multi-pomeron ($1\rightarrow 2, 2\rightarrow 3, 1\rightarrow 3$) vertices which describe how one pomeron may split into two or more. We use the Color Glass Condensate (CGC) formalism and JIMWLK evolution equation to derive explicit formulae for these vertices and show how this model can be used to study distribution of events with rapidity gaps in hard diffractive scattering in high energy proton-proton collisions.

Speaker: Jamal Jalilian-Marian (Baruch College)

16:30 Reconstructed jets within the partonic transport model BAMPS

Experimental data measured in $\sqrt{s}$ = 2.76 ATeV Pb+Pb collisions by the LHC experiments show a significant imbalance in the transverse momenta of the two leading reconstructed jets. This momentum imbalance is caused by the different in-medium path lengths and thereby different energy and momentum losses of the di-jets due to the passage through the created hot and dense matter. For investigating this momentum loss we extended the partonic transport model BAMPS which solves the full 3+1D Boltzmann equation for partons based on pQCD cross sections. Among the features of BAMPS is the stochastic modeling of both 2->2 and 2<->3 scattering processes by employing a new, improved Gunion-Bertsch matrix element together with a microscopic running coupling. In this talk we compare our recent results concerning reconstructed jets with different experiments and observables. To this end, we use well-established experimental background subtraction methods and have a closer look at the influence of the further recoil scattering processes of the initial shower partons on the momentum loss of the reconstructed jets.

Speaker: Florian Senzel (Goethe-Universität Frankfurt)

Poster Senzel_Poster_QM2014.pdf

16:30 Reconstruction of $\pi^{0}$ mesons via conversion method in Au+Au at 1.23AGeV with HADES

Lepton pairs emerging from decays of virtual photons represent promising probes of matter under extreme conditions. In the energy domain of 1 - 2 GeV per nucleon, the HADES experiment at GSI Helmholtzzentrum fuer Schwerionenforschung in Darmstadt studies di-electrons and strangeness production in various reactions, i.e. collisions of pions, protons, deuterons and heavy-ions with nuclei. An accurate determination of the medium radiation depends on a precise knowledge of the underlying hadronic cocktail composed of various sources contributing to the net spectra. Therefore, a measurement of the neutral meson yields together with the dileptons is crucial. In this contribution, the capability of HADES to detect $e^+e^-$ pairs from conversions of real photons will be demonstrated. We will present results from a two-photon analysis of Au+Au collisions at 1.23 GeV/u providing information on neutral $\pi^{0}$ mesons. Supported by BMBF (06FY9100I and 06FY7114), HIC for FAIR, EMMI, GSI, HGS-Hire and H-QM

Speaker: Claudia Behnke (U)

Poster QM_2014_Behnke.pdf

16:30 Reconstruction techniques for $\Lambda_{c} \rightarrow {\rm p}\overline{\rm K}^0$ in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the LHC

The study of open heavy flavour production is one of the most effective tools to investigate the properties of the strongly interacting medium created in heavy-ion collisions. For example, the baryon to meson ratio such as $\Lambda_{c}/{\rm D}$ offers the possibility to shed light on the thermalization and hadronization processes in the medium. An important baseline to interpret heavy-ion results is the comparison to other systems, such as pp and p-Pb. In particular, p-Pb collisions are the key to disentangle cold and hot nuclear matter effects which are present in A-A interactions. The focus of this poster will be on signal extraction techniques for the $\Lambda_{c} \rightarrow {\rm p} \overline{\rm K}^0$ decay channel in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The ALICE detector at the LHC, being the experiment dedicated to heavy-ion collisions, is able to resolve secondary vertices with high precision and resolution and to perform particle identification (PID) via various techniques over a very broad momentum range. These characteristics make it especially suitable for $\Lambda_{c} \rightarrow {\rm p}\overline{\rm K}^0$ analysis through the usage of reconstruction methods based on topological and PID selections. Performance studies of the application of multivariate analysis techniques based on the TMVA package will be also shown.

Speaker: Chiara Zampolli (Universita e INFN (IT))

Slides QM_poster_Lc_TMVA_AAlici_PHristov_CZampolli_SOFTColors_v13.pdf

16:30 Relaxation-time approximation and relativistic viscous hydrodynamics from kinetic theory

By employing Chapman-Enskog like expansion for the non-equilibrium single-particle phase-space distribution function, I solve iteratively the Boltzmann equation with relaxation time approximation for the collision term. I demonstrate that this method of obtaining the non-equilibrium distribution function has several welcome features in contrast to the widely used Grad's 14-moment approximation. Subsequently, by employing the distribution function thus obtained, I derive second-order hydrodynamic evolution equation for the shear stress tensor, directly from its definition [1]. This method of deriving the second-order viscous equation does not make use of the two major approximations/assumptions inherent in the traditional Israel-Stewart theory, namely, Grad's 14-moment approximation and second moment of Boltzmann equation. Eventually, I present the derivation of a novel third-order evolution equation for the shear stress tensor [2]. Within one-dimensional scaling expansion, I demonstrate that the results obtained here for the evolution of hot and dense matter are in excellent agreement with the exact solution of Boltzmann equation as well as the transport results. [1] A. Jaiswal, Phys. Rev. C 87, 051901(R) (2013) [2] A. Jaiswal, Phys. Rev. C 88, 021903(R) (2013)

Speaker: Amaresh Jaiswal (Tata Institute of Fundamental research, Mumbai)

Poster Amaresh_poster.pdf

16:30 Relics of Minijets amid Anisotropic Flows

Two dimensional low-pT dihadron correlations in azimuthal angle ϕ and pseudo-rapidity η in high-energy heavy-ion collisions are investigated within both the HIJING Monte Carlo model and an event-by-event (3+1)D ideal hydrodynamic model. Without final-state interaction and collective expansion, dihadron correlations from HIJING simulations have a typical structure from minijets that contains a near-side two-dimensional peak and an away-side ridge along the η-direction. In contrast, event-by-event (3+1)D ideal hydrodynamic simulations with fluctuating initial conditions from the HIJING+AMPT model produce a strong dihadron correlation that has an away-side as well as a near-side ridge. Relics of intrinsic dihadron correlation from minijets in the initial conditions still remain as superimposed on the two ridges. By varying initial conditions from HIJING+AMPT, we study effects of minijets, non-vanishing initial flow and longitudinal fluctuation on the final state dihadron correlations. With a large rapidity gap, one can exclude near-side correlations from minijet relics and dihadron correlations can be described by the superposition of harmonic flows up to the 6th order. When long-range correlations with a large rapidity gap are subtracted from short-range correlations with a small rapidity gap, the remaining near-side dihadron correlations result solely from relics of minijets. Low transverse momentum hadron yields per trigger (ptrig_T<4 GeV/c, passo_T<2 GeV/c) in central heavy-ion collisions are significantly enhanced over that in p+p collisions while widths in azimuthal angle remain the same, in qualitative agreement with experimental data.

Speaker: Dr LongGang Pang (Central China Normal University)

Poster QM2014_LGPang.pdf

16:30 Search for Antimatter Muonic Hydrogen at RHIC

In ultrarelativistic heavy-ion collisions, due to the high particle multiplicities, a produced muon can be bound to a charged hadron (proton, antiproton, $K^{+}$, $K^{-}$, $\pi^{+}$, $\pi^{-}$) by Coulomb force and form a hydrogen-like atom. Muon identification at low transverse momentum from the Time-of-Flight detector and the Time Projection Chamber provides STAR a great opportunity to search for a variety of muonic atoms. Muonic atoms are an ideal tool, as suggested by Mel Schwartz, Jack Sandweiss and the authors of [1] [2], to measure the thermal emission from the Quark-Gluon Plasma via a direct measurement of the single muon spectrum because only thermal muons or muons from short-lived resonance decays are capable of forming such atoms. We will present the analysis on the $\sqrt{s_{NN}}=200$ GeV Au+Au collisions collected by the STAR experiment at RHIC. Various methods and techniques will be shown to demonstrate the validity of search results. [1] Gordon Baym, Gerald Friedman, R. J. Hughes and Barbara V. Jacak, Phys. Rev. D 49, 4 (1993). [2] Joseph Kapusta and and Agnes Mocsy, Phys. Rev. C 59, 5, (1999).

Speaker: Kefeng Xin

Poster kxin_muonic_qm2014_v3.pdf

16:30 Search for intense magnetic field via dielectron asymmetry in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with ALICE at the LHC

A very intense U(1) magnetic field is expected to be created in relativistic heavy-ion collisions. The field in non-central Pb-Pb collisions at the LHC energy should reach about $10^{14}$ T. It is not only the most intense in the universe, far beyond the field on the surfaces of magnetars ($\sim 10^{11}$ T), but also is interesting in terms of fundamental physics as it is well above the critical magnetic field of electrons ($4 \times 10^9$ T) where non-linear behaviors of QED (e.g. photon splitting, real photons decaying into di-leptons, etc.) are theoretically expected. We have proposed new approaches to experimentally detect the field via a number of asymmetry measurements of dielectrons from direct virtual photons. The anisotropy of virtual photon decay, or the “polarization” of virtual photons, due to the field has been evaluated by QED calculations, and found possible to reach the order of $10^{-1}$. The status of the analysis in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV at ALICE will be presented, along with details of the theoretical evaluations and physics discussions.

Speaker: Kenta Shigaki (Hiroshima University (JP))

Poster qm14_20140520.pdf

16:30 Search for strong magnetic field via electron-pair asymmetry measurement in Au+Au at $\sqrt{s_{NN}}$ = 200 GeV at RHIC-PHENIX

Several models predict a strong magnetic field may be created in high-energy heavy-ion collisions by light-speed moving spectators and collision participants. The field can reach as high as $10^{14}$ teslas at RHIC, and rapidly decreases in a few fm/c. Such a strong field may exhibit charge distribution asymmetry with respect to the magnetic field direction that is orthogonal to the reaction plane, which has been investigated recently. According to theoretical calculation using vacuum polarization tensor in external magnetic field, virtual photon decay probability depends on the direction of strong field. This results in characteristic angular distributions of electron pairs with respect to the reaction plane. The effect is also dependent on centrality because the strength of the magnetic field changes over centralities. We look for the strong magnetic field effect via virtual photon decay, by taking advantage of an excellent electron-identification capability in PHENIX. Methods for background subtraction and signal extraction to detect the field are discussed.

Speaker: Mr TOMOYA HOSHINO (Hiroshima University)

Slides tomoya_QuarkMatter14_ver3.pdf

16:30 Self-consistent Cooper-Frye freeze-out of a viscous fluid to particles

Comparing hydrodynamic simulations to heavy ion data inevitably requires the conversion of the fluid to particles. This conversion, typically done in the Cooper-Frye formalism, is ambiguous for viscous fluids. We compute self-consistent phase space corrections by solving the linearized Boltzmann equation and contrast the solutions to those obtained using the ad-hoc ``democratic Grad'' ansatz typically employed in the literature where coefficients are independent of particle dynamics. Solutions are calculated analytically for a massless gas and numerically for both a pion-nucleon gas and for the general case of a hadron resonance gas. We find that the momentum dependence of the corrections in all systems investigated is best fit by a power close to $\frac{3}{2}$ rather than the typically used quadratic ansatz. The effects on flow coefficients are also calculated and found to be substantial for elliptic flow, thus the form of these corrections should be taken into account when extracting medium properties from experimental data.

Speaker: Zack Wolff (Purdue University)

Poster ZackWolff_poster_QM2014.pdf

16:30 Sensitivity of event plane correlations at large rapidity gap to $\eta$/s in heavy ion collisions

The event planes have played an important role in the experimental study of fluid dynamics and transport properties of the dense matter in heavy-ion collisions. Recently the correlation of different order event planes has also emerged as a promising tool to study the initial state of the high-energy nucleus-nucleus collisions. In the idealized case, event planes at different rapidities are completely correlated. However, initial parton production has significant fluctuations in the longitudinal direction as well as in the transverse direction. The longitudinal fluctuations of the initial transverse parton density can lead to fluctuations of the longitudinal azimuthal anisotropy at different rapidities and de-correlation of event planes with large rapidity gaps. In this work, we will explore the correlations of event planes of the same harmonics with different rapidity gaps in Pb+Pb collisions at $\sqrt{s_{\rm NN}}$ =2.76 TeV using two different dynamical models that incorporate initial conditions with longitudinal fluctuations in the initial energy density. The dynamical models used in our work are AMPT and a 3+1D ideal hydrodynamic model. The initial conditions for both models are given by the HIJING model that incorporates a Monte Carlo Glauber model for multiple nucleon interactions and two-component model for particle production. Particle production from soft coherent interaction of overlapping nucleons and incoherent semi-hard parton scatterings leads to fluctuations of local energy density in the transverse as well as longitudinal direction. In addition to the event plane correlations as a function of rapidity gap we will also discuss the sensitivity of the event plane correlation to transport properties and Equation of State (EoS) of the medium.

Speaker: Victor Roy (Central China Normal University)

Slides QM_poster_Victor.pdf QM_poster_Victor.ppt

16:30 Separation of electrons from charm- and beauty hadron decays in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with ALICE

The ALICE Collaboration at the LHC studies nucleus-nucleus collisions with the aim of investigating the properties of the high energy density state of strongly-interacting matter produced in heavy-ion collisions, the Quark-Gluon Plasma (QGP). Heavy quarks (charm and beauty) are an effective probe to investigate the properties of the QGP. They are produced almost exclusively in the initial partonic scattering processes and they interact strongly with the surrounding matter throughout its evolution. Moreoever, the in-medium parton energy loss is expected to depend both on the parton mass and its colour charge making flavour-separated measurements of charm and beauty useful to test models of in-medium energy loss. Experimentally one way to measure heavy quarks is via electrons from semileptonic decays of heavy-flavour hadrons. The comparison of the $p_{\rm T}$ spectra of heavy-flavour decay electrons in pp and Pb-Pb collisions gives insight into the energy loss of heavy quarks in the QGP. To achieve a flavour-separated measurement of heavy-flavour decay electrons, first the electrons have to be identified. This is done using the excellent particle identification capabilities of ALICE. In addition the electrons have to be separated according to their source (e.g. charm and beauty hadron decays, $\pi^{0}$ Dalitz decays, photon conversion etc.). This separation is done statistically using the impact parameter of the electrons. The latter is typically larger for electrons from hadrons containing a beauty quark due to the larger mean proper decay length ($c\tau\approx500 \mu \mathrm{m}$) of these hadrons compared to other hadrons decaying into electrons. In this poster the current status of the analysis is presented for pp collisions at $\sqrt{s}$ = 7 TeV and for Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV.

Speaker: Martin Völkl

Poster 2014-May-16-conferencefile-QMposterV8.pdf

16:30 Shear viscosity from a large-$N_c$ NJL model at next-to-leading order

Heavy-ion collisions at RHIC and LHC suggest that the shear viscosity to entropy ratio, $\eta/s$, is close to the AdS/CFT benchmark $1/4\pi$ indicating a strongly correlated state of matter produced in such collisions. The ratio $\eta/s$ is investigated in the vicinity of the chiral crossover using the two-flavor NJL model in a large-$N_c$ expansion. We study the non-perturbative structure of the NJL model and compare our approach to others such as kinetic theory. The issue of ladder resummation in the Kubo formalism and its relationship to the perturbative treatment of the model is examined. Dissipative contributions at next-to-leading-order to the shear viscosity lead to a pronounced minimum of $\eta/s$ above the AdS/CFT benchmark.

Speaker: Mr Robert Lang (TUM, RIKEN)

Poster QM2014RobertLANG.pdf

16:30 Shooting string holography of light quark jet quenching at RHIC and LHC

A new shooting string holographic model of jet quenching of light quarks in strongly coupled plasmas is presented [1,2] to overcome the serious inadequacies of previous falling string holographic scenarios especially at LHC. We will apply this framework to compute the nuclear modification factor RAA and the elliptic flow v2 and show that this model improves greatly the comparison with recent RHIC and LHC light hadron suppression data. We examine the effects of the Gauss-Bonnet quadratic curvature corrections to the AdS geometry and non-conformal dilaton deformations. Effects of fluctuations and first applications of this framework to heavy quarks will also be presented. [1] A. Ficnar, S. S. Gubser and M. Gyulassy, “Shooting String Holography of Jet Quenching at RHIC and LHC”, arXiv:1311.6160 [hep-ph] [2] A. Ficnar and S. S. Gubser, “Finite momentum at string endpoints”, Phys. Rev. D89 (2014) 026002, arXiv:1306.6648 [hep-ph]

Speaker: Andrej Ficnar (Columbia University in the City of New York)

Poster QM14Poster.pptx

16:30 Sign Structures of Susceptibilities of Conserved Charges in the (2+1) Polyakov Quark Meson Model

The rich sign structures of cumulants of conserved charges in the critical region are investigated in a QCD like model- the $\left(2+1\right)$ flavor Polyakov Quark Meson model. We compute all susceptibilities of the conserved charges on the $\mu_B-T$ plane upto fourth order and a few even higher orders. By varying the mass of the sigma meson, we are able to study and compare scenarios with as well as without a critical point. In the hadron-quark transition regime we identify certain correlations that turn negative unlike expectation from ideal hadron resonance gas calculations. These remain negative deep into the hadronic side and thus could be accessible to experiments. Measurements of such quantities in the heavy ion collision experiments can throw light on the location of the QCD transition curve as well as the critical point.

Speaker: Sandeep Chatterjee (National Institute of Science Education and Research)

16:30 Simulations with YaPT system for nucleus-nucleus collisions FAIR-GSI energies

Recently, an integrated on-line system for the study of the interactions in High Energy Physics, called YaPT, was developed at the calculation center of the Research Centre „Nuclear Matter in Extreme Conditions” [1]. Using this system, a systematic study of the Au-Au collisions at SIS-100 (FAIR-GSI) energies with a few simulation codes, as well as using a phenomenological geometric picture of the relativistic nuclear collisions [2,3] collisions was been done. Three types of charged particles were considered. The predictions of a few simulation codes (UrQMD, AMPT) were used for estimation in the mentioned model of the terms of the equation of state related to energy density, temperature and compressibility. The proton-proton collisions at similar energies have been used for comparisons. When possible, comparisons with existing experimental results at similar energies were included. The Rankine-Hugoniot equation permits estimations of the compressibility coefficient, the estimations being between 100 MeV and 1000 MeV. The estimations for viscosity coefficient, according to the model, indicated a significant increase from proton-proton collision to nucleus-nucleus collisions at the same incident energy. A small increase of this coefficient with the increase of the beam energy can be observed, too. A short analysis of the nuclear matter jets formation [4] in nucleus-nucleus collisions at these energies is done. Difference among the simulation codes predictions were observed, too. [1]. S.Cioranu, M.Potlog, Al.Jipa – accepted for publication in Rom.Rep.Phys.67(2015) [2]. Al.Jipa, C.Beșliu – Rev.Roum.Phys.33(1988)409, Rom.J.Phys.37(1991)1011 [3]. Al.Jipa – J.Phys.G22(1996)231 [4]. C.Beşliu et al - European Physical Journal A1(1)(1998)65-75

Speaker: A. Jipa (Faculty of Physics, University of Bucharest, Romania)

16:30 Soft and Hard interactions in proton-proton collisions at LHC energies

Non-diffractive proton-proton collisions can be classified into ``soft'' and ``hard'' (or ``semi-hard'') interactions, with hard (or semi-hard) interactions involving hard parton-parton interactions due to large momentum transfer resulting into jets, whereas interactions without a jet (or minijet) can be considered as soft interactions. Energy invariance in the properties of soft events (e.g. multiplicity, transverse momentum, and mean transverse momentum distributions) is observed at lower centre of mass energies [1,2]. We present a detailed study of the properties of soft and hard events at available LHC energies using various event generators. This study can further be extended to investigate the possibility of collectivity in proton-proton collisions at the LHC. Events are classified into soft and hard, based on presence of a jet. Sensitivity of various jet reconstruction algorithms ($k_{\rm T}$, $\rm anti-{{\it k}_T}$) and jet reconstruction parameters on the event classification are also investigated. [1] CDF Collaboration, Phys.~Rev.~D{\bf 65}, 072005 (2002). [2] Shengli Huang for the STAR Collaboration,\arXiv: nucl/Ex/0403038 (2004).

Speaker: Sidharth Kumar Prasad (Wayne State University (US))

Slides SoftHardInteractionsInpp_Sidharth.pdf

16:30 Soft direct photon $v_{2}$ and $n_{q}$ scaling

In heavy ion collisions at RHIC and the LHC, direct photons are produced in excess of their respective $T_{AA}$-scaled p+p spectra at low $p_T$ from 1-4 GeV/c. These results suggest early-stage thermal partonic emission from the hot dense medium. Additionally, these soft photons are produced with a large azimuthal anisotropy, an elliptic flow ($v_2$) as large as that of pions. Hydrodynamic models struggle to quantitatively reproduce the large soft photon $v_2$ because the pressure gradients that generate these anisotropies need time to develop, suggesting later-stage hadronic emission. The similarly-sized pion $v_2$ in this $p_T$ range is understood as resulting from the recombination of quarks near the phase transition as evidenced by quark number ($n_q$) scaling. In this poster, I present a coalescence-like model to describe the soft photon flow as the result of increased photon production from $q-\bar{q}$ interactions as the system approaches confinement. The published PHENIX soft photon and identified particle measurements are used to test this approach with both a $\chi^2$ analysis and comparison to model curves.

Speaker: Sarah Campbell (Iowa State University)

Poster QMPoster2014_PhotonFlow.pdf

16:30 sPHENIX Detector and Physics Program

Near the transition temperature, $T_C$, the strongly coupled QGP exhibits nearly inviscid flow. How the quantum-bounded low viscosity of QGP arises from the interactions of pointlike partons is not known in detail. Addressing this fundamental question experimentally requires measurements provided by scale-sensitive probes over a range of temperatures in the vicinity of $T_C$. Fully reconstructed jets, photons, and heavy flavor provide insight into the dynamics that underlie these properties of the QGP. The PHENIX collaboration is pursuing a major upgrade, sPHENIX, consisting of the BaBar superconducting solenoid, large acceptance hadronic and electromagnetic calorimetry and tracking. Coupled with fast data acquisition, sPHENIX will be able to make use of the full enhanced luminosity and species flexibility available at RHIC. The detector design also leverages modern developments in sensors and electronics---such as SiPMs and fast waveform digitization---and a novel calorimeter geometry to provide the needed capabilities in a cost-effective way. The measurements made possible by sPHENIX will complement those currently being made at the LHC, and will enable a comprehensive and exciting program of QGP measurements near $T_C$ in the region of strongest coupling.

Speaker: James Nagle (Unknown)

16:30 Statistical function instability under strong color magnetic field in 2PI approach

Important mechanisms of thermalization in relativistic heavy ion collisions are considered to be particle production and collision processes under the time dependent classical gluon fields and plasma instabilities. Non-equilibrium quantum field theory with 2 particle irreducible (2PI) effective action of pure Yang-Mills theory can describe the classical field and particle production/propagation in a unified manner, and provides a first-principle approach to the thermalization process. For example, time-dependent and/or inhomogeneous classical background fields allow rapid particle production, such as 1 to 2 process on the basis of the 2PI formalism. We calculate the time evolution of the statistical function which contains some important features of particle distribution under the homogeneous, but time dependent color electromagnetic fields in the lowest order of perturbation theory. Our results suggest that parametric resonance causes exponential growth of the statisical function in low momentum regions. We will also discuss the role of background color magnetic fields in the instability of the statistical function and Nielsen-Olesen instability as an underlying mechanism.

Speaker: Shoichiro Tsutsui (Kyoto University)

Poster QM2014_tsutsui.pdf

16:30 Statistically inferring nuclear modification of charm and beauty hadrons from PHENIX electron data

Quantitative knowledge of heavy quark momentum distributions in the hot nuclear medium created by ultrarelativistic heavy ion collisions is of high value in quantitatively understanding the quark-gluon plasma (QGP) phase of nuclear matter. In particular, the modification of heavy-quark momentum distributions from nuclear collisions as compared to smaller collision environments (such as p+p) provides important clues about the density of color charges and their coupling strength, which is of fundamental importance in QCD. This poster describes a procedure for statistical inference of D and B meson $p_{T}$ yields from nonphotonic electrons (NPEs). The relative yield of D and B mesons is sensitive to the electron $p_{T}$ and displaced-vertex distributions because of their mass and lifetime difference. The dataset is composed of an invariant NPE yield vs. $p_{T}$ as well as the electron displaced-vertex information, both measured near midrapidity. The yield of $D,B$ and subsequent decay ($D\to e$ and $B\to e$) is modeled using a monte carlo event generator (e.g. PYTHIA). Using real data and the generative model as inputs, the yield of parent mesons is inferred in a rigorous Bayesian framework using Markov Chain Monte Carlo sampling. The result is a full posterior distribution of D and B meson yields over a large $p_{T}$ range.

Speaker: Dr Andrew Adare (University of Colorado)

Slides adare-qm14poster.pdf

16:30 Status of Jet Reconstruction in Cu+Au collisions at 200 GeV from PHENIX

Arbin Timilsina for the PHENIX Collaboration Status of Jet Reconstruction in Cu+Au collisions at 200 GeV from PHENIX Jet reconstruction in heavy ion collisions is a vital tool to explore medium effects, including energy loss and modification of parton fragmentation functions. In 2012, making use of the unique capabilities of RHIC to collide different nuclei, the PHENIX experiment collected a large dataset of Cu+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Studying reconstructed jets in collisions of asymmetric heavy ions is crucial in understanding the interplay between collision geometry and initial and final state effects. In central Cu+Au collisions, the Cu nucleus is completely embedded within the Au nucleus. The study of Cu+Au collisions as a function of centrality can help disentangle the 'core' of the collision region, characterized by a large energy density, and the outer 'corona' region. We will present the status of jet reconstruction in Cu+Au and a reference sample of p+p collisions at 200 GeV using the anti-kT algorithm.

Speaker: Mr Arbin Timilsina (Iowa State Univeristy)

Poster QM2014_Poster_Final.pdf

16:30 Status of the FAIR Synchrotrons

The unique facility for Antiproton and Ion Research – FAIR will deliver stable and rare isotope beams covering a huge range of intensities and beam energies. The construction of the modularized start version of FAIR has been started. Major civil construction measures, e.g. the site preparation and the drilling of the 60 m deep building foundations are presently being implemented. Procurement of components of the accelerator facilities with long production times has been launched and the design and set-up of the corresponding series test facilities at GSI and CERN are under preparation. The design and status of superconducting magnets, rf-systems, injection and extraction systems and beam diagnostics of the heavy-ion synchrotrons will be presented.

Speaker: Carsten Omet (GSI Helmholtzzentrum für Schwerionenforschung mbH)

Slides Status_of_FAIR_Synchrotrons_Poster_Quark_Matter.pdf Status_of_FAIR_Synchrotrons_Poster_Quark_Matter.pptx

16:30 Status of the NICA project at JINR

The NICA (Nuclotron-based Ion Collider fAcility) project is now under active realization stage at the Joint Institute for Nuclear Research (JINR, Dubna). The main goal of the project is an experimental study of hot and dense strongly interacting matter in heavy ion collisions at centre-of-mass energies √s_NN = 4 - 11 GeV (NN-equivalent) and the average luminosity of 10E27 cm-2 s-1 for Au(79+) in the collider mode (NICA collider). In parallel, the fixed target experiment BM@N at the JINR superconducting synchrotron Nuclotron is in preparation stage. Extracted beams of various nuclei species up to Au(79+) with maximum momenta 13 GeV/c (for protons) will be available. The NICA project also foresees a study of spin physics with extracted and colliding beams of polarized deuterons and protons at the energies up to √s = 26 GeV (for protons). The proposed program allows to search for possible signs of the phase transitions and critical phenomena as well as to shed light on the problem of nucleon spin structure. General design and construction status, physical program of the NICA complex is presented.

Speaker: Vladimir Kekelidze (Joint Inst. for Nuclear Research (RU))

16:30 Strange and electromagnetic probes of dense nuclear matter at SIS

We present transport-model simulations of proton-nucleus and nucleus-nucleus collisions at SIS energies, primarily focusing on electromagnetic and strange observables in order to learn about the properties of mesons in a dense nuclear medium. Dilepton and kaon spectra measured by the HADES detector at GSI are being confronted with transport simulations obtained with the GiBUU model. In this way we find indications for a nonzero kaon potential in p+Nb as well as the need for significant in-medium modifications of the $\rho$ meson's spectral function in Ar+KCl collisions. Further, we discuss the intricacies of handling such in-medium effects in a transport approach.

Speaker: Dr Janus Weil (FIAS)

16:30 Strangeness production in nuclear collisions around the threshold

We review the production of strange hadrons in nuclear collisions in which the collision energy pre nucleon is below or just slightly above the threshold for strangeness production. First, a statistical model is formulated in which the exact conservation of strangeness and averaging over impact parameter can properly be handled. The observed data are compared with the predictions of the model and the right amount of underprediction is obtained. Then, kinetic model for hadron production is formulated and constrained by the observed data on kaon production. The yields of Phi and Xi are calculated and compared to the data. Possible effects necessary for the description of the data are discussed.

Speaker: Boris Tomasik (Univerzita Mateja Bela (SK))

Poster poster_TomasikKoloVoskr.pdf

16:30 STRONG FLUCTUATIONS IN INITIAL CONDITIONS FOR INTERACTIONS OF HEAVY AND LIGHT NUCLEI AT JINR-AGS-SPS ENERGIES

Estimation of fluctuations in initial conditions of nuclei interactions is one of the key problems for heavy ion physics. Right solution can be obtained, using correlations between multiplicity and sum of all, – light and heavy, - fragment-spectators (Fig a). Great significance of heavy fragment analysis has already been pointed out in the works of NA-49 (H. Appelshauer, 1998) and NICA (M. Golubeva, 2013), BNL 2012 RHIC&AGS Annual Users’ Meeting ”eRHIC – understanding the initial condition of the heavy ion”. In the present work investigation of initial conditions for interactions of light – (C, O, Ne), medium - (Si, S) and heavy – (Au, Pb) nuclei with heavy – (Ag/Br) and light – (C/N/O) nuclei have been analyzed on the data of JINR-AGS-SPS target emulsion experiments with limited statistics. The analysis example for interaction Si (14.7) and S (200) A GeV with (C/N/O) nuclei is presented on fig. Detection of both shower particles and fast fragment-spectators with identical possibilities in this method open the way to the useful study of this problem. The analysis has shown, that nonlinearity in the multiple and fragmentation processes to become stronger with the impact parameter increasing. Physical explanation of the fluctuation growing consists in new effect creation – nonregularity in the production of heavy fragment-spectators with intermittent mass distribution (Fig c, d, top). Fluctuations in this case correspond to the Levy flights, but not small Gaussian variations in a data series around the mean. Integrally the patterns of heavy and light fragmentation are totally different. In the proton fragmentation mass distributions have the most smoothly – Gaussian-like – behavior both in central and peripheral interactions (Fig d, c, d, below). New process, - the strong intermittent behavior in the heavy mass fragment distributions with high probability occur in colliding of light nuclei. Conclusions can be useful in the understanding processes of heavy ion physics and new experiments designing.

Speaker: Albert Loctionov (Institute of Physics and Technology)

Slides https://cloud.mail.ru/public/81e9533dbce1/poster_MQ_2014_Loc.pdf

16:30 Studies of the hadronic calorimeter prototype for sPHENIX

High energy heavy ion collisions at RHIC create strongly coupled, hot, dense matter (quark-gluon plasma), which performs like a perfect fluid. Fundamental questions such as how and why the quark-gluon plasma behaves as a perfect fluid in the vicinity of the critical temperature, can only be fully addressed with world-class jet observables at RHIC energies. Jet probes in medium are crucial to understand the coupling of the quark gluon plasma, the origin of this coupling, and the mechanism of rapid equilibration. During past three years, the PHENIX collaboration has developed a detector development plan for the next decade, referred as sPHENIX, which will incorporate electromagnetic (EMCAL) and hadronic (HCAL) calorimeters with a large pseudo-rapidity range, and full azimuthal coverage. The HCAL will be first large coverage hadronic calorimeter ever to be used at RHIC, and will enable a systematic study of jets in quark-gluon plasma. A novelty accordion inspired HCAL prototype based on scintillator plates and steel absorber plates has been constructed and tested using test beam at Fermilab. It has two longitudinal sections, and a total depth of 5 interaction length. In this poster, we will present the test beam performance, and single particle GEANT 4 simulation studies for the HCAL prototype.

Speaker: Dr LIANG XUE (Georgia State University)

16:30 Study of $\Lambda^{\ast}$(1520) resonance production with the ALICE experiment at the LHC

We report $\Lambda^{\ast}$(1520) production in pp collisions at $\sqrt{s}$ = 7 TeV and in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV by ALICE at the LHC. The study of $\Lambda^{\ast}$ production is important because its lifetime is comparable to the lifetime of the fireball and it contains all three light quarks (uds) as valence quarks. The study of $\Lambda^{\ast}$ production can also be used to investigate the medium between chemical and thermal freezeout, since its decay products may interact with the hadronic medium. In this poster presentation we will show mass, width and transverse momentum spectra both in pp and p-Pb systems. The ratio of $\Lambda^{\ast}$ over $\Lambda$(1115) is expected to be the same in p-Pb as in pp collisions; it will be compared to that measured at RHIC energies and to the prediction from the thermal model in Pb-Pb collisions.

Speaker: Rama Chandra Baral (Institute of Physics (IN))

Poster Lambdastar_poster_Lambda1520.pdf

16:30 Study of $\rm D^{0}$ signal extraction in ALICE using combinatorial background subtraction techniques

Charm and beauty quarks are powerful probes to investigate the properties of the Quark-Gluon Plasma (QGP) produced in high-energy heavy-ion collisions. Due to their large mass, they are produced in the initial hard scattering processes and thus they experience the whole evolution of the system formed in the collision. They interact strongly with the deconfined medium, losing energy and possibly participating in the collective expansion. The precise measurement of the nuclear modification factor ($R_{\rm AA}$) and the elliptic flow ($v_{2}$) of D mesons in Pb-Pb collisions provides a stringent constraint to theoretical models describing the interaction of heavy quarks with the medium. The standard procedure for the reconstruction of D mesons, via their hadronic decay channels, in ALICE is based on the selection of displaced secondary vertices, which rejects a large part of the combinatorial background. A complementary approach has been recently studied, in which less stringent selections are applied and the background is subtracted using the event-mixing, like-sign or track-rotation techniques. We will present the status of the studies on the $\rm D^{0}$ signal extraction at low $p_{\rm T}$ in pp and p-Pb collisions at $\sqrt{s_{\rm NN}} =$ 7 TeV and 5.02 TeV, respectively, using this complementary approach.

Speaker: Chitrasen Jena (Universita e INFN (IT))

Slides lowpTD0_QM2014_CJena.pdf

16:30 Study of charm jet tagging using ${\rm D}^{\ast +}$ mesons with ALICE in pp collisions at the LHC

Heavy-flavour hadrons and jets are effective probes for the characterisation of the strongly interacting matter formed in high-energy heavy-ion collisions, known as Quark-Gluon Plasma. Tagging jets by looking for a D meson within their cone provides a sample of jets originating from charm quark fragmentation and thus allowing us to improve our understanding of heavy-quark fragmentation, both in pp and Pb-Pb collisions. This poster presents the strategy and the observables under study, together with the current status of the D$^{*+}$-jet correlation measurement in pp collisions at $\sqrt{s} = 8$ TeV. The high statistics required for D-meson measurements and jet spectrum corrections demand for a large data sample. In 2012, the ALICE experiment recorded pp events triggering with its electromagnetic calorimeter, hence preferentially selecting events with jets and heavy-flavour signals. A set of Monte Carlo studies is presented with the aim of assessing the feasibility of the measurement in pp with the current data and with larger integrated luminosities in pp and Pb-Pb collisions as they are expected to be available from Run 2 at the LHC.

Speaker: Chiara Bianchin (University of Utrecht (NL))

Slides DStarInJetQM14_CBianchin.pdf

16:30 Study of dielectron production in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV using Transition Radiation Detector triggers with the ALICE detector

The primary role of the ALICE experiment at the LHC is to investigate the properties of the deconfined state of matter, the quark-gluon plasma (QGP), created in relativistic heavy-ion collisions. Electron-positron pairs (dielectrons) are excellent probes for studying the properties of the medium. They are produced during the entire evolution of the system and carry the information of the medium since they are not affected by the strong interaction. Correlated electron-positron pairs from semi-leptonic decays of heavy quarks are the dominant source of dielectrons in the intermediate and high mass region above 1 GeV/$c^2$. Heavy quarks are mainly produced in the initial hard scatterings and are sensitive to the transport properties of the medium. A correct understanding of heavy-ion results requires, in addition, an evaluation of initial state nuclear effects, through the study of p-Pb collisions. In the ALICE experiment, the Transition Radiation Detector (TRD) is used for the electron identification above $p > 1$ GeV/$c$ momentum. The TRD also provides an electron trigger to enrich the data samples for the study of charmonium and open heavy flavor production. In 2012, ALICE has successfully collected p-Pb collisions with TRD trigger ($L_{\rm int}$ = 1.4 nb$^{-1}$) , allowing us to extend the invariant mass spectrum of dielectrons to higher pair $p_{\rm T}$ and mass. In this poster, the current status of the dielectron analysis with the TRD triggered data in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented.

Speaker: Shinichi Hayashi (University of Tokyo (JP))

16:30 Study of gamma-gamma interactions in pPb collisions at LHC with CMS

Di-lepton production in photon-photon collisions is a benchmark process that allow for precise determination of the luminosity at the LHC. In particular in collisions, where at least one of the nuclei is a lead nucleus, the photon fluxes are large enough to make efficient use of it. In this analysis di-muon production during the pPb run in 2013 is analysed using dedicated triggers. Any hadronic contribution is removed by stringent exclusivity requirements. Yields of selected di-muon events are compared to high precision theoretical calculations of electromagnetic particle production from photon-photon collisions in the very periphery of the colliding nuclei.

Speaker: Melike Akbiyik (KIT - Karlsruhe Institute of Technology (DE))

Slides QM_poster_v04.pdf

16:30 Study of high-$p_{\rm T}$ neutral mesons with a high energy photon trigger at ALICE

ALICE is one of the experiments at LHC and is mainly dedicated for heavy-ion collisions to investigate properties of a deconfined state of matter, Quark-Gluon Plasma (QGP). High $p_{\rm T}$ particle production is expected to be a powerful tool to study the QGP. The hadron yields in nucleus-nucleus collisions can be quantified by the nuclear modification factor, which is the ratio of the particle yield in A-A collisions normalized to the number of inelastic nucleon-nucleon collisions to the yield in pp collisions. The $R_{\rm AA}$ at high $p_{\rm T}$ is significantly smaller than 1, which can be interpreted by the parton energy loss. The ALICE experiment has a high resolution and high granularity photon spectrometer PHOS which deploys a specific trigger to enhance the high-$p_{\rm T}$ photon and neutral pion detection capability. Neutral pion production in pp collisions at $\sqrt{s}=8$ TeV has been studied. PHOS triggered data is used in this data analysis. With using this PHOS triggered data taken in 2012, neutral pion can be measured up to 40 GeV/c. To evaluate the production cross-section of the neutral pions with PHOS triggered data, trigger response of the PHOS needs to be understood as a function of the reconstructed cluster energy. A way to evaluate the trigger response utilizing the minimum-bias data as a function of the cluster energy has been developed. Neutral pion trigger efficiency is then estimated with simulation. A method to evaluate the rejection factor with real data is developed. These techniques can be applied to other collision systems, too. In this presentation, the status of analysis of the PHOS triggered data in pp collisions at $\sqrt{s}$ = 8 TeV will be presented.

Speaker: Satoshi Yano (Hiroshima University (JP))

Poster QM_poster_syano_v4.pdf

16:30 Study of neutral $\pi$ meson in $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV p-Pb collisions at ALICE

Quark-Gluon Plasma (QGP) which is believed to have existed in a very early universe, is a high temperature and dense matter. The ALICE experiment is optimized for heavy-ion collisions and intended to explore the property of QGP. The study of hadron production is essential for the properties of QCD matter. In p-Pb collisions at a high energy region, it enables estimation of the initial state of collisions in the QGP generation. We analyzed minimum-bias triggered data measured by the ALICE photon spectrometer PHOS in $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV p-Pb collisions. In order to confirm the energy calibration of PHOS, the energy-to-momentum ratio for electron was measured and a particularly conspicuous non-linearity effect at low $p_{\rm T}$ region was evaluated. The energy of electrons was measured by PHOS and their momentum was measured by the central tracking system. In addition, we discuss $\pi^{0}$ reconstruction in PHOS via invariant mass analysis of photon pairs. $\pi^{0}$ meson raw spectrum is obtained via a signal peak extracted from the invariant mass distribution. The geometrical acceptance of PHOS and reconstruction efficiency for $\pi^{0}$ meson were evaluated with Monte-Carlo calculations. We present the efficiency corrected $\pi^{0}$ yield.

Speaker: Tsubasa Okubo (Hiroshima University (JP))

Slides QM2014_TsubasaOkubo_v5.pdf

16:30 Study of non-prompt $J/\psi$ production from B decays in pp collisions with the PHENIX Detector at RHIC

A major objective in the field of heavy ion collisions is to quantify and characterize the properties of QGP by studying heavy flavor production. The $J/\psi$ meson can be produced in one of three ways: 1) directly in the collision, 2) indirectly via feeddown from heavier charmonium states, or 3) from the decay of B mesons. If the $J/\psi$ is produced through either of the first two methods, it is called a prompt $J/\psi$, while the third method produces a non-prompt $J/\psi$. With the newly commissioned forward silicon vertex detector (FVTX) in 2012, it is possible for the first time at the PHENIX experiment to extract non-prompt $J/\psi$'s from the inclusive $J/\psi$ signal by measuring a displaced vertex. In this poster, we will present the current status of the data analysis for $J/\psi$'s that come from B decays in pp collisions at $\sqrt{s_{_{NN}}}=510$ GeV with the PHENIX experiment at RHIC. Results of this analysis will provide a proof-of-principle for future measurement in heavy ion collisions.

Speaker: Margaret Jezghani (Georgia State University)

16:30 Study of single electron production in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV triggered with the ALICE Transition Radiation Detector

In high-energy nucleus-nucleus collisions, heavy-flavour quarks, i. e. charm and beauty, are produced on a very short time scale in initial hard scattering processes and thus they experience the whole history of the collision. Therefore, they are valuable probes to study the mechanisms of energy loss and hadronisation in the hot and dense state of matter, that is expected to be formed in the collision. In order to investigate these medium effects proton-proton (pp) and proton-nucleus (p-A) collisions are measured as reference. While the first collision system allows one to test pQCD calculations and to establish the reference for Pb-Pb and p-Pb collisions, the latter gives access to cold nuclear matter effects, e. g. parton scattering in the initial state and modifications of the parton densities in the nucleus. Heavy-flavour production can be measured in hadronic and semi-leptonic decay channels with ALICE at the LHC. However heavy quarks (charm and beauty) are rare probes, which makes differential and detailed studies difficult. At mid-rapidity, the ALICE Transition Radiation Detector (TRD) can be used to select events with electrons at trigger level, to significantly enrich samples of electrons originating from open heavy-flavour and quarkonia decays. The TRD electron trigger was successfully in use in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV allowing us e.g. to improve the single electron measurements at intermediate $p_{\rm T}$. First results will be shown in comparison with the analyses based on the recorded minimum bias data sample.

Speaker: Yvonne Chiara Pachmayer (Ruprecht-Karls-Universitaet Heidelberg (DE))

Poster pachmayer_poster_qm2014.pdf

16:30 Study of the transverse momentum distribution of jet constituents in p-Pb collisions at ALICE

Jet properties are influenced by both perturbative and non-perturbative processes that take place during the jet fragmentation. Transverse momentum distributions in jets provide insight into the gluon radiation patterns in jet fragmentation. At the Tevatron it was found that the distribution of the component of the momentum transverse to the jet axis ($j_{\rm T}$) of jet constituents agrees well with the Next-to-Modified Leading Log Approximation (NMLLA). It is also very important to study the $j_{\rm T}$ distribution at the LHC energy range in order to investigate possible modifications induced by cold nuclear matter. The cold nuclear medium produced in the p-Pb collisions could alter the initial state radiation shower evolution and thus the inter- and intra-particle correlations are expected to be broadened. In this contribution we present the $j_{\rm T}$ spectra of charged jet constituents from the analysis of the fully reconstructed jets in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV measured by the ALICE experiment. The jets are reconstructed using anti-$k_{\rm T}$ algorithm from charged particles and clusters in electromagnetic calorimeter. The results of $j_{\rm T}$ distribution will be shown for multiple jet virtuality bins and compared to the existing data from the Tevatron.

Speaker: Jiri Kral (University of Jyvaskyla (FI))

Slides jk_jt_qm_v7_small.pdf

16:30 Studying Dilepton Production from SIS to RHIC Energies: Transport Calculations vs. Coarse-grained Dynamics

Lepton pairs at low mass from heavy-ion collisions are considered good probes for chiral symmetry restoration and the in-medium properties of vector mesons. However, the broad variety of their sources requires models that can describe the complete nuclear reaction properly. For this, transport approaches (e.g. the UrQMD model) are frequently used, as they yield a realistic microscopic description of the collision dynamics. However, such microscopic models usually do not include any in-medium effects and are limited to hadronic degrees of freedom. We therefore present an alternative approach that uses coarse-grained output from transport calculations to extract local thermodynamic properties and determine thermal dilepton emission rates. The approach has the advantage that it can cover all collision energies and the whole space-time evolution in a unified description. To account for the medium effects on the $\rho$ meson we apply and contrast the spectral function by Eletsky et al., which is obtained from empirical scattering amplitudes, and the many-body calculation by Rapp et al. We present results for SIS, SPS and RHIC energies and compare them to experimental data as well as the outcome from hydrodynamic and pure transport calculations.

Speaker: Stephan Endres (Frankfurt University / Frankfurt Institute for Advanced Studies)

Poster poster.pdf

16:30 System integration of the Silicon Tracking System for the CBM experiment at FAIR

The Silicon Tracking System will be installed into the superconducting dipole magnet, providing sufficient aperture to receive it's 2 m$^3$ volume, the vacuum chamber with target and Micro Vertex Detector, and the beam pipe. The detector system breaks down into eight tracking stations, built from a total of 106 carbon fiber ladders with 896 detector modules comprising 1220 silicon microstrip sensors, a total of about 2 millon read-out channels. The system integration effort is presented to mount the ladders with high mechanical accuracy and stability. The sensors will be operated at -5 $^\circ$C, to be achieved with a gas flow. The read-out electronics dissipates about 40~kW which will be evacuated with a CO2 cooling system. Solutions to route the supplies and services in the confined space will be discussed, as well as precautions to enable access to the components in case of repair.

Speaker: Tomas Balog (GSI)

Poster CBM-STS-poster-T.Balog.pdf

16:30 Systematic studies of the centrality dependence of soft photon production in $Au+Au$ collision with PHENIX

Since the earliest days of Heavy Ion Physics thermal soft photon radiation emitted during the reaction had been theorized as a *smoking gun* signal for formation of a quark-gluon plasma and as a tool to characterize its properties. In recent years the existence of excess photon radiation in heavy ion collisions over the expectation from initial hard iteractions has been confirmed at both RHIC and LHC energies by PHENIX and ALICE respectively. There the radiation has been found to exhibit elliptic flow $v_2$ well above what can currently be reconciled with a picture of early emission from a plasma phase. During the 2007 and 2010 $Au+Au$ runs PHENIX has measured a high purity sample of soft photons down to $p_T>0.4\,\mathrm{GeV}/c$ using an external conversion method. We present recent systematic studies by PHENIX from that sample on the centrality dependence of the soft photon yield, and elliptic and triangular flow $v_2$ and $v_3$ in $Au+Au$ collisions which fill in the experimental picture and enable discrimination of competing soft photon production scenarios.

Speaker: Benjamin Bannier (Stony Brook University)

Poster poster_qm2014.pdf

16:30 The ALICE Muon Forward Tracker Upgrade Project

The ALICE experiment is dedicated to the study of the quark gluon plasma in heavy-ion collisions at the CERN LHC. The Muon Forward Tracker (MFT), an internal tracker added in the acceptance of the existing Muon Spectrometer ($2.5 < \eta < 4$), will be part of the ALICE detector upgrade program to be put in place during the LHC shutdown planned for 2019. The precise measurement of the offset to the primary vertex for the muon tracks, allowed by the MFT, will permit for the first time in ALICE the identification of open charm ($c\tau \sim 150~\mu$m) and beauty ($c\tau \sim 500~\mu$m) production at forward rapidity, rejecting at the same time a large fraction of background muons coming from pion and kaon decays. The setup of the MFT is an assembly of circular planes made of Monolithic Active Pixel Sensors (MAPS), to be installed between the interaction point and the hadron absorber of the Muon Arm. The total material budget of the MFT tracking planes, the radiation hardness of their components, coupled with the high granularity of the sensors and the envisaged readout speed, fulfill the conditions for the operation at the energies and luminosities foreseen for the LHC heavy-ion program after 2019. The expected detector performances resulting from realistic simulations of the MFT setup will be shown, together with the various technological issues related to the project.

Speaker: Lizardo Valencia Palomo (Univ. Blaise Pascal Clermont-Fe. II (FR))

Poster MuonForwardTracker.pdf

16:30 The Binder cumulant in O(N)-models

The phase structure of QCD is currently a much discussed topic in particle physics. In the context of this discussion we need precise knowledge about the nature of the chiral phase transition. A powerful tool to investigate it are lattice simulations. They are, however, still restricted to relatively large quark masses, far from the chiral limit, and to small volumes, which could affect the critical behavior. These two facts complicate the scaling analysis of lattice QCD results. In the chiral limit, a continuous phase transition is expected in two-flavor QCD. Since continuous phase transitions are controlled by the long range fluctuations, only the dimensionality and symmetries dictate the universal behavior near the critical point. Therefore, more simple systems from the same universality class can be investigated in order to describe scaling behavior which is expected at the chiral phase transition in lattice QCD. Because the long range fluctuations play such a prominent role at continuous phase transitions, it is self-evident that it is useful to investigate precisely the behavior of higher-order critical fluctuations close to the transition point. For this purpose the so-called Binder cumulants seem to be very well suited. We analyze the fourth-order Binder cumulant in 3-dimensional O(2)- and O(4)-models in finite volumes using non-perturbative Renormalization Group methods. This approach allows us to gain explicit insight into the behavior of the critical fluctuations and provides a tool which assists in analysis of lattice QCD data.

Speaker: Mr Paul Springer (Technische Universität München)

Poster poster.pdf

16:30 The CBM-RICH detector

The Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR) will explore the phase diagram of nuclear matter at very high net-baryon densities and moderate temperatures. It is designed for operation in fixed target mode to study ultrarelativistic nucleus-nucleus collisions at beam energies up to 45 AGeV with unprecedented statistical precision. An important CBM observable are light vector mesons and charmonium which are experimentally accessible via their decay into lepton pairs. Those are ideal probes of the early, high-density phase of the collision process due to their lack of strong interaction with the hot and dense medium. The measurement of such rare probes requires clean and efficient electron identification which will be provided up to momenta of 8 GeV/c by a gaseous Ring Imaging Cherenkov (RICH) detector. The main challenges are the suppression of pions and the precise control of the background in the high multiplicity environment of a heavy ion collision. We will present the detector concept developed to meet the requirements and the recent progress in R&D resulting in the CBM-RICH Technical Design Report which has been approved by FAIR in February 2014. Results from in-beam tests with a real-size prototype will be discussed which verify the detector concept and validate the feasibility studies done so far.

Speaker: Jan Kopfer (University Wuppertal)

Poster QM2014_CBM-RICH_Kopfer.pdf

16:30 The Chiral Criticality in the Probability Distribution of Conserved Charges

Statistical fluctuations of the net baryon number and electric charge have been regarded as an excellent diagnostic tool of the chiral phase transition in QCD and in heavy ion collisions [1]. While the second order cumulant exhibits divergence at the critical endpoint, the higher order cumulants can reveal remnants of the $O(4)$ criticality at the chiral crossover [2]. We will discuss criticality in the probability distribution of conserved charges close to the chiral transition. We calculate the probability distribution of the net baryon number $P(N_B)$ in the chiral quark-meson model within the functional renormalization group method, and compare its properties to the non-critical Skellam function [3,4]. We will show, that the ratio of $P(N_B)$ to the Skellam distribution exhibits a characteristic narrowing which is due to remnants of the $O(4)$ chiral transition [4]. We will apply the above analysis to the experimental data measured by STAR collaboration, and show that STAR data taken at the most central events exhibit a similar narrowing as found in the model calculations [4]. We will indicate a relevant reference distribution for the net electric charge fluctuations. We show that the binomial and negative binomial distribution cannot account for the characteristic behavior seen in the chiral transition, and that due to quantum statistics and multi-charged particle contribution, the Skellam distribution is also not a correct baseline for the recent STAR data on fluctuations of the electric charge [4]. [1] M. Stephanov, K. Rajagopal, E. Shuryak, Phys. Rev. Lett. **81**, 4816 (1998). [2] B. Friman, F. Karsch, K. Redlich, V. Skokov, Eur. Phys. J. C **71**, 1694 (2011). [3] K. Morita, B. Friman, K. Redlich, V. Skokov, Phys. Rev. C **88**, 034903 (2013). [4] K. Morita, B. Friman, K. Redlich, in preparation.

Speaker: Dr Kenji Morita (Frankfurt Institute for Advanced Studies)

Slides qm14_poster_morita.ppt

16:30 The deconfinement phase transition in simulations of relativistic nuclear collisions

We present fluid dynamical simulations of relativistic nuclear collisions, augmented with a finite-range term, to study the effects of the phase structure on the evolution of the baryon density. For collision energies that bring the bulk of the system into the mechanically unstable spinodal region of the phase diagram, the density irregularities are being amplified significantly. The resulting density clumping may be exploited as a signal of the phase transition. We also present a quantitative discussion on some specific observables (nuclear cluster creation and two particle angular correlations), which might be sensitive to the expected clustering of the net baryon density. Our results are a first step towards identifying unambigous experimental signals for a first order transition in dense nuclear matter.

Speaker: Jan Steinheimer

Poster Poster1_steinheimer.pdf

16:30 The electromagnetic signature of the IP-Glasma initial state

Currently the IP-Glasma initial state, coupled with a viscous hydrodynamic evolution, provides the best description of hadronic flow coefficients and their fluctuations in heavy ion collisions [1]. In this work we perform the first calculation of electromagnetic radiation using IP-Glasma initial conditions. We include the contributions from pQCD photons arising from the initial hard scatterings at the early stages of the collision, and we go beyond the usual popular formulations of the fluid evolution by using a Israel-Stewart viscous hydrodynamical description that takes into account all second order terms, including those related to bulk viscous pressure. We also highlight the effect of initial flow, which appears naturally in the IP-Glasma profile. We investigate how such additional theoretical ingredients affect the electromagnetic spectra, as well as the azimuthal anisotropy coefficients. More specifically, we check how these features help in explaining the large values of photon elliptic and triangular flow observed by the PHENIX and ALICE collaborations. We further investigate how a simultaneous fit of hadronic and electromagnetic observables can enhance agreement with data of the latter without compromising the interpretation of hadron data. [1] C. Gale, S. Jeon, B. Schenke, P. Tribedy, R. Venugopalan, Phys. Rev. Lett. 110 (2013)

Speaker: Jean-Francois Paquet (McGill University)

Poster poster.pdf

16:30 The fluidity of a hot hadronic soup

The ratio η/s of the shear viscosity, η, and the entropy density, s, of hot interacting hadrons is calculated using the Chapman-Enskog and virial expansion methods. Interactions are parametrized using the K-matrix which preserves the unitarity of the S-matrix. In the four component mixture π-K-η-N , 57 resonances up to 2 GeV are included. Increasing number of resonances is shown to reduce η and increase s resulting in a progressive decrease of η/s for temperatures close to the QCD phase transition temperature. Prospects of hot hadrons becoming a “perfect” fluid are discussed.

Speaker: Dr Anton Wiranata (CCNU)

Poster QM2014.pdf

16:30 The Forwards-Backwards Asymmetry of Charged Particles in pPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with CMS

The forwards-backwards asymmetry ($Y_{asm}$) of inclusive charged particles is reported as a function of transverse momentum in pPb collisions at $\sqrt(s_{NN})$=5.02 TeV as measured with the CMS detector. These asymmetries are constructed from the charged particle transverse momentum spectra measured for 0.4 < $p_T$ < 100 GeV/c, and in six pseudorapidity classes ranging from 0.3 to 1.8. In addition, the asymmetry is presented in classes of event activity determined by the total energy measured in the forward hadron calorimeter.

Speaker: Krisztian Krajczar (CERN)

Slides QM14_poster_Krajczar_v2.pdf

16:30 The Magneto-Sono-Luminescence and its signatures in photon and dilepton production in heavy ion collisions

I introduce a novel mechanism for anisotropic photon and dilepton production in heavy ion collisions, stemming from the interplay between the fluctuations of gluonic matter, fermonic loops and the existence of strong (electro)magnetic fields. A particular example of this mechanism is tied with the conformal anomaly of QCD and described by the hydrodynamical bulk modes of QCD plasma. I show that it leads to the photon production yield that is comparable to the yield from conventional sources. Furthermore, this mechanism provides a a significant positive contribution to the azimuthal anisotropy of photons (v2) and shows agreement with the PHENIX data.

Speaker: Gokce Basar (Stony Brook University)

16:30 The Microsecond universe and the neutron star

It is entirely plausible, that a first order QCD phase transition under a reasonable condition occurred from quarks to hadrons when the universe was about a microsecond old. It is shown in this paper that the quark nuggets, possible relics of the first order QCD phase transitions with baryon number larger than $10^{43}$ will survive the entire history of the universe uptil now and can be considered as candidates for the cold dark matter. The spin down core of the neutron star on the high density low temperature end of the phase diagram initiates transition from hadrons to quarks. As the star spins down, the size of the core goes increasing. Recently discovered massive Pulsar PSRJ 1614-2230 with a mass of 1.97$\pm$0.04 $M_{\odot}$ most likely has a strongly repulsive interacting quark core. What possible observables can there be from these neutron stars? One of the central question we ask, the infant universe and the core of the neutron star, do they have properties of a perfect fluid?

Speaker: Bikash Sinha (Variable Energy Cyclotron Centre, Kolkata, India)

16:30 The onset of pion condensation in heavy-ion collisions at the LHC energies

Statistical models of hadron production have become one of the cornerstones of our understanding of ultra-relativistic heavy-ion collisions [1]. However, the measured proton abundances in Pb+Pb collisions at sqrt(sNN) = 2.76 TeV at LHC do not agree with the most common versions of the thermal models. Besides the proton anomaly, the same LHC data exhibits the low-transverse-momentum enhancement of pion spectra by about 25-50% with respect to the predictions of various thermal and hydrodynamic models [2]. In the recent work [3] we connect the proton anomaly with the pion enhancement effect and show that the two problems may be solved naturally within the statistical model which assumes chemical non-equilibrium at the freeze-out and a special combination of freeze-out geometry and flow - the Krakow single-freeze-out model in the Monte-Carlo version implemented in THERMINATOR [4]. We find a remarkable agreement between our model and the measured transverse-momentum spectra of pions and kaons. Although the protons are not included in the fit, our model explains well their spectrum, in addition to their yield. We also find a satisfactory description of hyperons with the same parameters. Correct description of the low-transverse-momentum enhancement of pions within our model suggests that it may be interpreted as a signature of the onset of pion condensation in ultra-relativistic heavy-ion collisions at the LHC energies. This is so, since the freeze-out conditions in the model are very close to the pion condensation point. [1] P. Braun-Munzinger, D. Magestro, K. Redlich, J. Stachel, Phys. Lett. B 518, 41 (2001). [2] B. Abelev et al. [ALICE Collaboration], Phys. Rev. Lett. 109, 252301 (2012); Phys. Rev. C 88, 044910 (2013). [3] V. Begun, W. Florkowski, M. Rybczynski, arXiv:1312.1487 [nucl-th]. [4] M. Chojnacki, A. Kisiel, W. Florkowski and W. Broniowski, Comput. Phys. Commun. 183, 746 (2012).

Speaker: Dr Viktor Begun (UJK)

Poster Begun_poster_QM_2014.pdf

16:30 The performance of the ALICE High Momentum Particle Identification Detector in pp, p-Pb and Pb-Pb collisions

The High Momentum Particle Identification Detector (HMPID) is specifically developed for track-by-track particle identification in ALICE. The HMPID is a ring imaging Cherenkov detector with an active area of 10.5 m$^2$ of caesium iodide photo-cathodes installed in MWPC-s filled with pure methane. It identifies $\pi^{\pm}$ and K$^{\pm}$ in the momentum range $1-3$ GeV/$c$, and p in the range $1.5-5$ GeV/$c$. The performance of the photo-cathodes during LHC Run1 period (2010-2013) has been investigated by the analysis of data from pp and p-Pb collisions. The number of reconstructed photons shows that there was no caesium iodide quantum efficiency loss (ageing), which is consistent with the measured integrated charge dose of $0.0133$ mCcm$^{-2}$. A Monte Carlo procedure is ongoing to extract the quantum efficiencies, from the first results we found that no significant difference between the extracted quantum efficiencies and the measured ones at the production time of the photo-cathodes (2003). The performance of statistical and track-by-track particle identification have also been investigated. The statistical PID was successfully applied to the measurement of inclusive hadron production in pp collisions at $\sqrt{s} = 7$ TeV. The purity and contamination of particles have been extracted from Hijing Monte Carlo generated events (Pb-Pb at $\sqrt{s_{\rm NN}} = 2.76$ TeV) and used as an input for the ongoing physics studies using track-by-track PID

Speaker: Laszlo Olah (Hungarian Academy of Sciences (HU))

Poster Olah_QM2014_poster.pdf

16:30 The PHENIX Forward Silicon Vertex Detector

After more than a decade of discovery physics at RHIC, major questions still remain concerning QCD color screening and the exact mechanisms governing parton energy loss in the nuclear medium that is created in ultrarelativistic collisions of large nuclei. To answer these questions, the PHENIX experiment has developed and installed a new silicon detector which dramatically enhances the capabilities of the existing PHENIX muon spectrometer. The Forward Silicon Vertex Tracker (FVTX) consists of over a million 75$\mu$m-wide silicon ministrips, read out by custom ASIC chips, and provides precise charged particle tracking at forward and backward rapidity. With data taken during the 2012 and 2013 runs at RHIC, the FVTX has demonstrated single hit efficiencies greater than 95% and a hit position resolution better than 30$\mu$m. This poster will discuss the design, construction, and operation of the FVTX detector at PHENIX.

Speaker: J. Matthew Durham (Los Alamos National Laboratory)

16:30 The production of low mass dielectrons in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 GeV from STAR

Dileptons in the low mass region, ($M_{ll} < 1.1 {\rm GeVc}^{-2}$), retain information about vector mesons that originated in the strongly interacting matter created by relativistic heavy-ion collisions. Linking these vector mesons to an in-medium broadening of their spectral functions may suggest chiral symmetry restoration[1]. Measurements at SPS and RHIC energies have been made in the low mass region that are consistent with in-medium modification of the $\rho$ meson spectral function. By using RHIC's beam energy scan (BES) program and its high-purity, large-acceptance electron identification, STAR has been systematically studying the production of low mass dielectrons as a function of collision energy. We present the preliminary results of the low mass dielectron production in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 GeV. The study is focused on the comparison of the spectra with the expected hadronic contributions and with models that include production from $\rho$ with an in-medium modified spectral function and medium radiation. In addition, the results will be compared with previously presented measurements from other BES energies ($\sqrt{s_{NN}}$ = 19.6, 39, and 62.4 GeV) and projections for future BES-2 measurements will be presented. [1] R.Rapp and J.Wambach, Advances in Nuclear Physics 25(2000).

Speaker: Frank Geurts (Rice University (US))

Poster QM2014Poster.pdf

16:30 The puzzling relation between the $R_{AA}$ and the $v_2$ for heavy mesons in a Boltzmann and in a Langevin approach

The heavy quarks constitutes a unique probe of the quark-gluon plasma properties. Both at RHIC and LHC energies it has been observed a puzzling correlation between the nuclear modification factor $R_{AA}$ and the elliptic flow $v_2$ that has challenged all the existing models, especially for D mesons, We discuss how the treatment of the charm quark dynamics according to a Boltzmann or a Langevin dynamics can be responsible for a large part of such a puzzle. In particular, we see that depending on the angular and temperature dependence of the scattering matrix the $v_2$ can be quite different. In particular, once one reproduces the $R_{AA}$ with both a Boltzmann and/or a Langevin approach the $v_2(p_T)$ that is build-up can be as different as a 50-80%. This together with a coalescence hadronization mechanism strongly quenches the puzzling $R_{AA}$ and $v_2$ observation. Differences between Boltzmann and Langevin dynamics can be traced back to the fact that especially for large screening mass (nearly isotropic scatterings) the transferred momentum is not small but comparable with the charm mass as well as to the average momentum of the bulk. On the other hand such differences disappear for bottom quarks which are predicted to be free of the ambiguities coming from the difference between a Boltzmann or a Langevin approach, and should more properly considered as heavy quarks as regards their transport in the QGP. Our study allows also to shed lights on the different predictions of several models currently compared with the first data at LHC on D mesons. Reference: 1) S. K. Das, F. Scardina, V. Greco, arXiv:1312.6857 [nucl-th] 2) H. Van Hees, M. Mannarelli, V. Greco and R. Rapp, Phys. Rev. Lett.100,192301 (2008) 3)V. Greco, C. M. Ko and R. Rapp, Phys. Lett. B 595,202 (2004)

Speaker: francesco scardina (INFN Catania)

Poster poster_scardina_finale.pdf poster_scardina_finale.pptx

16:30 The Role of Initial-state Geometry and its Fluctuations in Hadronic Collisions

It will be demonstrated that initial-state geometry and its attendant fluctuations play a central and consistent mechanistic role for collective anisotropic flow, jet quenching and the space-time expansion dynamics of the matter created in collisions at RHIC and the LHC. The implications of this mechanistic role for the extraction of several transport and thermodynamic coefficients will be discussed.

Speaker: Roy Lacey (Stony Brook University)

16:30 The role of the quark-gluon vertex function in the QCD phase transition

The quark-gluon vertex function, describing the (non-perturbative) interactions of quarks with gluons, plays a central role in and is subject to dynamical chiral symmetry breaking. Accordingly, its change across the QCD crossover transition drives on the one hand important aspects of the phase transition and on the other hand its structure changes substantially. Results for the quark-gluon vertex at vanishing temperature within the Dyson-Schwinger formalism in Landau gauge are presented and a generalization to non-vanishing temperatures is discussed. A simplified system (scalar QCD) is investigated at both vanishing and non-vanishing temperatures. This allows to introduce a novel order parameter for the center phase transition.

Speaker: Markus Hopfer (Karl-Franzens University Graz)

16:30 The STAR Muon Telescope Detector Upgrade

The 2014 RHIC run marks the complete installation of the Muon Telescope Detector (MTD) by the STAR Collaboration. This detector upgrade is based on long Multi-gap Resistive Plate Chambers (MRPCs) which have been mounted outside STAR's magnet yoke. The MTD provides a coverage of 45% in azimuth over almost one unit of pseudorapidity, centered around mid-rapdity . The detector, in combination with other mid-rapidity detectors and the newly installed Heavy Flavor Tracker, will enable STAR to accurately address a wide range of physics that involve dilepton and heavy-flavor probes. In this poster, we will present the physics prospects of the MTD upgrade, as well as a first glimpse at its performance in the present RHIC 200 GeV Au+Au heavy-ion run.

Speaker: Frank Geurts (Rice University (US))

16:30 The study of jet properties in pp collisions at 7 TeV and pPb collisions at 5.02 TeV using POWHEG-Box

Recent experimental results on jet production at LHC show that next-to-leading order (NLO) calculations are required to achieve good description of data. In this contribution, the study of NLO simulations of jet production in proton-proton collisions with centre of mass energy of 7 TeV and proton-lead collisions at 5.02 TeV is presented. These simulations were carried out using POWHEG-Box, implementation of positive weight hardest emission NLO generator, with parton showering provided by PYTHIA. In pPb collisions the nuclear modification of parton distribution functions was implemented by EPS09 nuclear parton distribution modification factors. Jet reconstruction was done using standard anti-k$_{T}$ algorithm, included in the FastJet package. Several values of resolution parameter $R$ were used to cover range of experimental results. For parton distribution functions, CTEQ6.6 datasets were used for unmodified values, and NLO modification factors to simulate modification by lead nucleus. We present the calculations and systematic studies of jet production cross sections and comparison of modified and unmodified jet yields, $R_{pPb}$. These observables provide information about effect of expected cold nuclear matter on observed jets and the results are compared to available data from LHC experiments.

Speaker: Michal Vajzer (Acad. of Sciences of the Czech Rep. (CZ))

Poster QM2014_vajzer_poster.pdf

16:30 The thermodynamics of heavy light hadrons at freezeout

In the discussion of hadronization at or close to the freeze-out curve, statistical (hadron resonance gas) models play an important role. In particular in the charmonium sector, regeneration models are considered which rely on the fact that charmonium states can form again already at temperatures well above the QCD crossover or hadronization temperature. An important ingredient in these considerations is the regeneration or hadronization of open charm states. In this talk we report on a lattice QCD analysis of correlations of open strangeness [1] and charm [2] with other conserved quantum numbers like the net baryon number and electric charge. We analyze the temperature range in which an uncorrelated hadron resonance gas (HRG) provides an adequate description of such correlations. This limits the range of validity of HRG based thermodynamics in open flavor channels and provides an estimate for the melting temperature of heavy-light hadrons. We find that the strange or charmed HRG description breaks down at or very close to the QCD crossover temperature. References: [1] A. Bazavov, H.-T. Ding, P. Hegde, O. Kaczmarek, F. Karsch, E. Laermann, Y. Maezawa, Swagato Mukherjee, H. Ohno, P. Petreczky, C. Schmidt, S. Sharma, W. Soeldner and M. Wagner (Bielefeld-BNL collaboration) "Strangeness at high temperatures: from hadrons to quarks" Phys. Rev. Lett. 111, 082301 (2013). [2] Bielefeld-BNL collaboration, to be published.

Speaker: Dr Sayantan Sharma (Bielefeld University)

Poster ssharma_qm.pdf

16:30 The Time Evolution of the Distribution of Matter in Hard Particle Production

The violent production of a hard, colored object in hadronic collisions causes drastic--but perturbatively calculable--changes to the vacuum. We quantitatively explore this modification of the vacuum produced by strong interactions by explicitly computing the full time and spatial dependence of the QCD energy-momentum tensor associated with a hard production event. The derivation adapts the finite temperature, many-body technology of the Schwinger-Keldysh formalism to scattering problems in perturbative QCD in T = 0 empty space. Applications of our calculation include the creation of a hybrid early-time pQCD/late-time AdS/CFT energy loss model; novel predictions for particle production in high-energy QCD scattering; and new tests of the distribution of matter, energy, and momentum in jets in pp collisions and the redistribution of matter in jets in heavy ion collisions.

Speaker: Mr Ben Meiring (University of Cape Town)

Poster conference_poster_Meiring.pdf

16:30 The Tricky Azimuthal Dependence of Jet Quenching at RHIC and LHC via CUJET2.0=rcDGLV+elastic+VISH(2+1)

We present a $\chi^2/d.o.f.$ analysis of RHIC and LHC $R_{AA}$ ($p_T>10$ GeV/c) and $v_2$ ($p_T>10$ GeV/c) data using the new open C++ source CUJET2.0 code [1] developed as a component of the DOE JET collaboration project. The code evaluates jet path integral involving running coupling DGLV induced radiated gluon energy loss rates as well as elastic energy loss for jets propagating though viscous hydrodynamics VISH 2+1D expanding thermal fields $T(x,y,t)$ constrained by fits to bulk low $p_T$ observables. We compare numerical results as a function of our main control parameter, $\alpha_{max}$, an assumed upper bound on the vacuum running coupling in the infrared. A $\chi^2/d.o.f.$ analysis shows that $R^\pi_{AA}$ data from RHIC and LHC are consistent with CUJET2.0 at the $\chi^2/d.o.f.< 2$ level for $\alpha_{max}=0.22-0.27$. The corresponding $\hat{q}(E_{jet}, T)/T^3$ effective jet transport coefficient field of this model is evaluated and compared to other (HT-BW, HT-M, MARTINI, McGill-AMY) JET collaboration models [2]. We focus here on the main current jet quenching puzzle (not discussed in [2]) the underestimation of jet elliptic asymmetry, $v_2(p_T)$ at both RHIC and LHC by CUJET and most other pQCD based tomographic models. We show that relaxing the assumption that $\alpha_{max}$ is independent of the local T field can reduce the $v_2$ discrepancy between CUJET and data to the $\chi^2_{v_2}/d.o.f.< 2$ level by allowing as small as $10\%$ variations of the path averaged $\alpha_{max}(T(z))$ along in and out paths. We speculate about origin of such variations and propose additional future tests to help elucidate the "tricky azimuthal dependence" of jet quenching seen at RHIC and LHC. References [1] Jiechen Xu, Alessandro Buzzatti, Miklos Gyulassy, "Azimuthal Jet Flavor Tomography with CUJET2.0 of Nuclear Collisions at RHIC and LHC", arXiv:1402.2956. [2] The JET Collaboration, "Extracting jet transport coefficient from jet quenching at RHIC and LHC", arXiv:1312.5003.

Speaker: Jiechen Xu (Columbia University)

Poster QM14-Poster-Final.pdf

16:30 The velocity of pions in the low-temperature phase of QCD

The dispersion relation of the pion quasiparticle is calculated in the confined phase of QCD with two light flavors of quarks using lattice simulations. In the hadron gas, the would-be diffusion pole of the axial charge density and the Goldstone boson of chiral symmetry breaking "mix"; as a result, a single light quasiparticle emerges whose dispersion relation can be determined from equilibrium quantities (D.T. Son and M. Stephanov, Phys. Rev. D66 (2002) 076011). Results are presented for temperatures between $0.7T_c$ and $T_c$.

Speaker: Mr Daniel Robaina (Institute of Nuclear Physics, University of Mainz)

16:30 Thermal fluctuations in heavy ion collisions

The thermal fluctuations inherent in viscous hydrodynamics are significant when examining a fluid either at small length scales or near a critical point. Both of these conditions can be met in ultra-relativistic heavy-ion collisions. These fluctuations have small but non-vanishing effects on observables at the Relativistic Heavy-Ion Collider (RHIC) and at the Large Hadron Collider (LHC). Because the amplitudes of the fluctuations are related to viscosity through the fluctuation-dissipation relation, the effects of fluctuations on observables may lead to an independent measurement of transport coefficients in quark-gluon plasma. Numerical simulation of the propagation of thermal noise is necessary even in the linearized limit, and can be used to examine the effect of thermal fluctuations on observables.

Speaker: Clint Young (University of Minnesota)

Poster CYoungQM2014.pdf

16:30 Thermodynamics and phase structure of strongly-interacting matter

Polyakov-loop-extended constituent-quark models are useful to investigate the phase structure and thermodynamics of strongly-interacting matter. We show that taking into account the quark backreaction on the gauge-field dynamics as well as quantum and thermal fluctuations of quarks and mesons is crucial in such models to achieve results for order parameters and thermodynamics that are in line with lattice calculations at vanishing chemical potential. Achieving a good agreement with non-perturbative calculations at zero density, we extend the investigations to nonzero quark density and isospin. We present the impact of unquenching effects in the Polyakov-loop potential on the phase structure at non-vanishing quark densities and show predictions for thermodynamics at nonzero isospin. We test the reliability of those models by confronting its results with lattice data on the isospin dependence of the transition temperature. Furthermore, we investigate the phase structure of the three-dimensional temperature - isospin - quark density phase diagram and calculate the surface tension for the phase transition at small temperatures and large densities.

Speaker: Rainer Stiele (Heidelberg University)

Poster Poster_RS_QM.pdf

16:30 Thermodynamics of a Solvable Quark Model Inpired by the Gribov-Zwanziger Theory

In an attempt to solve the problem of spurious gauge copies in the path integral approach to gauge theories, V. N. Gribov proposed in 1978 a method to restrict the integration domain of the path integral to only one gauge field representative of each physical field configuration. As a result, the quadratic part of the gluon propagator is modified in the infrared, so that it acquires complex poles, i.e., complex "masses". This implies the absence of gluons in the physical spectrum, which is a necessary condition for confinement. An analogous reasoning may be applied to quark fields coupled to the gauge fields. As a consequence, the quark propagator also gets modified in the infrared, giving rise to unphysical propagators (i.e., with complex poles) at small momenta. Such a property is understood as a sign of both quark confinement and of the breaking of chiral symmetry in the vacuum. In this work, we study the thermodynamics of this model by exactly calculating the partition function using standard methods of finite-temperature quantum field theory. We find that the infrared behavior of the quark propagator leads to a highly nontrivial pressure as a function of the temperature, which is qualitatively close to the results from lattice QCD at finite temperature.

Speaker: Bruno Mintz (Universidade do Estado do Rio de Janeiro - Brazil)

16:30 Title: The centrality dependence of jet and leading particle production in d-Au and p-Pb collisions

We take a detailed look at high transverse momentum (high $p_T$) particle and jet production in d-Au collisions at RHIC and p-Pb collision at LHC. In particular, we study the correlation between jet production and the number of charged particles produced, which allows collisions to be binned in centrality. While Hulthen distributions are used to sample the spatial distribution of nucleons in deuteron, nucleon distributions within the larger nucleus are sampled form either correlation-free Woods-Saxon or shell model distributions with nucleon-nucleon correlations. The collision of a nucleon from the deuteron with a column of nucleons in the nucleus is carried out by modifying the PYTHIA event generator. Two methods are presented: one retains exact isospin conservation (prior to weak decays) by tracking each nucleon-nucleon collision and another with exact energy conservation where the energy of a column of $N$ nucleons is incorporated within a single ``super'' nucleon by enhancing the parton distribution functions by $N$. In either case, the energy lost in the production of the jet pair is taken into account exactly. Both methods also include a new implementation of a transverse density dependent event-by-event shadowing. The results for high $p_T$ particle production, binned in centrality by the number of charged particles produced, is compared with experimental results from PHENIX on high-$p_T$ neutral pion production in d-Au collisions, with a focus on the observed enhancement in peripheral collisions.

Speaker: Michael Kordell (W)

Poster qm2014poster.pdf qm2014poster.pptx

16:30 Towards the continuum limit of thermodynamics from lattice QCDwith dynamical charm

We present first results achieved within a recently started project dealing with lattice QCD thermodynamics in the presence of two dynamical quark generations. We explore temperatures ranging from 150 to 650 MeV employing the twisted mass discretization for Wilson-type quarks and following a fixed-lattice scale approach at three different lattice spacings in order to control the approach to the continuum limit. The effect due to the inclusion of the second quark generation is studied by comparing with previously obtained two-flavour results.

Speaker: Dr Ernst-Michael Ilgenfritz (JINR Dubna, VBLHEP and BLTP)

16:30 Towards the Test of Saturation Physics Beyond Leading Logarithm

Earlier this year, we published the first numerical calculation to incorporate all next-to-leading order (NLO) corrections for the forward pion production cross section in pA collisions. Our calculation gives a good description of existing results from RHIC at $p_\perp$ up to the saturation scale. I will present an overview of the calculation, review the results for RHIC as compared to the experimental data, and present our predictions for the LHC's heavy ion program. I'll also discuss an interesting issue in which, at larger $p_\perp>Q_s$, the results of the prediction become negative, and review the progress of our attempts to cure the negativity, including by resumming higher-order terms of the cross section.

Speaker: David Zaslavsky (Penn State University)

Paper Research presented in this poster is based on this published paper and followup work

Poster Poster

16:30 Transport coefficients of QGP

We study the transport properties of strongly interacting matter in the vicinity of the phase transition for different effective models, i.e. the Nambu-Jona-Lasinio (NJL) model and the Dyniamical QuasiParticle Model (DQPM) for 3 quark flavours. We present our results on the temperature dependence of the shear and bulk viscosity (calculated within the relaxation time formalism), as well as of the electric and heat conductivity in comparison to recent lattice data [1]. These transport coefficients allow for discussing quantitatively how fast particles traverse the quark gluon plasma and open the possibility to compare different approaches for the expansion of the quark gluon plasma created in ultrarelativistic heavy-ion collisions. The comparison of the final observables (multiplicity, v_2, v_3, \dots) for realistic simulations based on these models are presented within the Parton-Hadron-String Dynamics (PHSD) and the Relativistic quantum molecular dynamics for Strongly interacting matter with Phase transition or crossover (RSP) [2]. [1] Phys. Rev. C 88, 045204 (2013) [2] Phys. Rev. C 87, 034912 (2013)

Speaker: Elena Bratkovskaya (FIAS)

Poster Poster_Marty.pdf

16:30 Transport model studies on reconstructed jets in a hot partonic medium

Within a multiphase transport model, several experimental observables related to reconstructed jets, including the transverse momentum imbalance for photon-jet, transverse momentum asymmetry for dijet, jet fragmentation function, jet shape, and jet flow, are investigated in Pb+Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV. Because the imbalance ratio between photon and jet is sensitive to both production position and passing direction of photon, it could enable a detail tomographic study on the hot partonic medium by selecting different imbalance ratio ranges [1]. Dijet asymmetry evolution functions disclose that final dijet asymmetry is driven by both initial dijet asymmetry and partonic jet energy loss [2]. The measured jet fragmentation function in Pb+Pb collisions is decomposed into two parts from jet fragmentation and coalescence, which indicates a competition between the two jet hadronization mechanisms that dominate different $\xi$=ln(1/$z$) ranges and different centrality bins [3]. The subleading jet shape displays a larger medium modification than the leading jet shape, especially in more central Pb+Pb collisions with a larger dijet asymmetry [4]. Azimuthal anisotropies (or flows) of jets ($v_2$ and $v_3$) are sensitive to the geometry asymmetry of initial partonic distribution, which is consistent with a path-length dependence of jet energy loss in the QGP [5]. All these results support that jets lose much energy owing to the strong interactions between jets and a hot partonic medium. References: [1]Guo-Liang Ma, Phys. Lett. B, 724 (2013) 278 [arXiv: 1302.5873]. [2]Guo-Liang Ma, Phys. Rev. C, 87 (2013) 064901 [arXiv: 1304.2841]. [3]Guo-Liang Ma, Phys. Rev. C, 88, (2013) 021902(R) [arXiv: 1306.1306]. [4]Guo-Liang Ma, Phys. Rev. C, 89 (2014) 024902 [arXiv: 1309.5555]. [5]Mao-Wu Nie and Guo-Liang Ma, in preparation.

Speaker: Guo-Liang Ma (Shanghai INstitute of Applied Physics (SINAP), CAS)

Slides QM2014_Jet_MaGuoliang.pdf

16:30 Tri-hadron Azimuthal Correlations and the Conical Emission by Strong Color Fields without Collective Flow in p+p and p+Pb Collisions

The azimuthal angular correlations ("ridge") were well-known from the A+A collisions where the collimation of the hadrons in the azimuthal angle was ascribed to the collective flow of the Quark Gluon Plasma (QGP). The di-hadron correlations in the high multiplicity p+p and p+Pb collision events from the CMS experiment revealed a ridge structure that was very much like the ones from the A+A collisions. These results, which were not predicted by Monte Carlo based QCD simulations, attracted great interest since the formation of QGP and consequently a collective flow were not anticipated in p+p and p+Pb collisions. Soon after the report of the CMS collaboration, it was shown that this ridge can be explained by the multiladder QCD diagrams ("glasma diagrams") that were enhanced at the saturation scale at small-x. By means of these diagrams, the two particle gluon production rate can be written in terms of the unintegrated gluon distribution functions (UGD) of the colliding hadrons (or hadron and nucleus). Then, the UGD that is extracted from the running coupling BK equation (rcBK) is substituted in this formula. Later these correlated two gluons can be related to the observed di-hadrons via fragmentation functions. The strength of azimuthal correlations depends on the momenta and relative azimuthal angle of the di-hadrons as well as the saturation scale. It should be emphasized that this framework does not demand any collective flow to explain the data. Despite the excellent agreement between the data and the results of the glasma diagrams, however, the analyses employing the collective flow and the application of hydrodynamics to p+p and p+Pb collisions are also successful. Hence, this puzzle demands a study of tri-hadron correlations that may possibly settle the origin of the ridge in p+p and p+Pb events. Tri-hadron correlations will also put the Color Glass Condensate and saturation physics to more stringent test. We calculate tri-hadron correlations from the glasma diagrams by using the rcBK UGDs for p+p ($\sqrt{s}=$7 TeV) and p+Pb ($\sqrt{s}=$5.02 TeV) collisions for several values of the momenta and relative azimuthal angle of the trigger and two associated hadrons. We repeat these calculations for different values of the saturation scale to predict the systematics of the track multiplicity of the actual measurements. Our tri-hadron azimuthal correlation results show that the glasma diagrams give rise to structures similar to the conical emission or Mach cone that have been discussed previously in the context of A+A collisions. However, we see these structures not only on the away side but also on the near side as distinguished from the Mach cone in A+A collisions which occur only on the away side. The azimuthal correlations due to the multiladder gluon production (glasma) are also clearly distinguished from the correlation structures that might be caused by other medium effects such as energy loss and jet deflection. We make quantitative predictions for the high multiplicity tri-hadron azimuthal correlations for p+p and p+Pb collisions at LHC. These tri-hadron correlations have not been measured yet by the experimental collaborations.

Speaker: Dr Sener Ozonder (Institute for Nuclear Theory, University of Washington)

Poster poster-Sener-Ozonder.pdf

16:30 Triangular Flow of Inclusive Charged and Identified Particles at RHIC

Triangular flow ($v_{3}$), the third harmonic of the azimuthal particle distribution relative to the event plane, is getting more attention in recent years. It is considered that $v_{3}$ is generated by event-by-event initial state fluctuations. Therefore, it is natural to use $v_{3}$ as a tool to study initial state fluctuations and the subsequent evolution of the collision system. Another aspect of identified-particle $v_{3}$ measurements is the study of the energy dependent difference between particles and anti-particles $v_{3}$. That is especially important after the observation of a difference in elliptic flow between particles and anti-particles in Beam Energy Scan data at STAR. We present $v_{3}$ measurements from STAR of identified particles ($\pi^\pm$, $K^\pm$, $p$, $\bar{p}$, $\phi$, $\Lambda$ and $\bar{\Lambda}$) relative to the third-order event plane as a function of $p_\mathrm{T}$ for different centralities (0\%-80\%, 0\%-10\%, 10\%-40\%, and 40\%-80\%) at $\sqrt{s_\mathrm{NN}} =$ 27 GeV, 39 GeV and 200 GeV. We discuss the hydrodynamics-inspired mass ordering at low $p_\mathrm{T}$ ($p_\mathrm{T} < $ 1.5 GeV/c), number-of-consitituent-quarks scaling at intermediate $p_\mathrm{T}$ (0.5 GeV/c $ < p_\mathrm{T}/n_\mathrm{q} < $ 1.5 GeV/c), and the difference between particles and anti-particles as a function of centrality and beam energy. We also present $v_{3}$ for charged hadrons relative to the first-order event plane which is determined from spectator neutrons at $\sqrt{s_\mathrm{NN}}=$ 200 GeV Au+Au and 193 GeV U+U collisions. As this type of event plane represents the reaction plane instead of the participant plane, it helps us to understand the origin of triangular flow.

Speaker: Xu Sun (Lawrence Berkeley National Laboratory)

Slides Xu_QM2014.pdf

16:30 Tsallis blast-wave analysis in relativistic heavy ion collisions

In the high-energy nuclear collisions at RHIC, it has been clear evidenced the formation of the hot and dense matter with strong collectivity developed during the entire collision evolution, driven by intense rescattering among the fireball constituents. The measurable observables that can provide information about thermalization and collective flow are the transverse momentum spectra of produced particles. We will present a study of blast-wave fits using Tsallis statistics performed on the measured transverse momentum spectra obtained in Au-Au collisions at RHIC energies as a function of rapidity and collision centrality. In addition, comparisons with predictions for relativistic heavy ion collisions using the most important simulation codes at the future CBM-FAIR energies will be presented to provide more detailed insights on the properties of the space-time evolution such as collective dynamics of the dense matter.

Speaker: Dr Oana Ristea (Faculty of Physics, University of Bucharest)

16:30 Two-Gluon Correlations in Heavy-Light Ion Collisions

We derive the cross-section for two-gluon production in heavy-light ion collisions in the saturation/Color Glass Condensate framework. This is the first-ever two-gluon production calculation including saturation effects to all orders in one of the nuclei (heavy ion) along with a single saturation correction in the projectile (light ion). The calculation of the correlation function predicted (qualitatively) two identical ridge-like correlations, near- and away-side. This prediction was later supported by experiment findings. Concentrating on the energy and geometry dependence of the correlation functions we find that the correlation function is nearly center-of-mass energy independent. The geometry dependence of the correlation function leads to an enhancement of near- and away-side correlations for the tip-on-tip U+U collisions when compared with side-on-side U+U collisions, an exactly opposite behavior from the correlations generated by the elliptic flow of the quark-gluon plasma.

Speaker: Douglas Wertepny (The Ohio State University)

Poster wertepny_QM2014.pdf

16:30 Two-loop perturbative corrections to the thermal effective potential in gluodynamics

The thermodynamics of pure glue theories can be described in terms of an effective action for the Polyakov loop. This effective action is of the Landau-Ginzburg type and its variables are the angles parametrizing the loop. We compute perturbative corrections to this action. Remarkably, two-loop corrections turn out to be proportional to the one-loop action, independent of the eigenvalues of the loop. By a straightforward generalization of the 't Hooft coupling this surprisingly simple result holds for any of the classical and exceptional groups.

Speaker: Dr Yun Guo (Universidade de Santiago de Compostela)

Poster Yun_Guo-qm2014poster.pdf

16:30 Two-pion Femtoscopy Measurements at RHIC-PHENIX

Two-pion femtoscopy measurements provide invaluable insights on the expansion dynamics and the space-time extent of the emitting source produced in nucleus collisions at RHIC and the LHC. Recent PHENIX measurements now span a broad range of beam collision energies ($\sqrt{s_{NN}}=39-200$ GeV) and system sizes (d+Au, Cu+Cu and Au+Au). Results from these new measurements will be presented as a function of collision centrality and the mean transverse momentum of pion pairs, for different collision systems and beam collision energies. They provide new insights on reaction dynamics at RHIC, as well as a detailed model independent mapping of the evolution of the space-time extent of the emitting source, from RHIC to LHC.

Speaker: alex mwai (Stony Brook University)

Poster QM2014_HBTScalingv2.pdf

16:30 Universal scaling dependence of QCD energy loss from data-driven studies

In Pb-Pb collisions a dense partonic state of matter, the Quark Gluon Plasma, is formed. Jets created in a collision probe the medium, but so far the experimental results on jet quenching cannot be reproduced theoretically: existing QCD models fail to describe both $R_{\text{AA}}$ and $v_{\text{2}}$ consistently at high $p_{T}$. In this talk a data driven study using Glauber simulations for the initial geometry is presented. We find that the energy loss depends linearly on the initial path length (RMS) and as square root of the initial density. Surprisingly, the density scaling found for LHC data also explains the RHIC data. Finally, the possible implications of these results for a full theoretical modeling are discussed.

Speaker: Vytautas Vislavicius (Lund University (SE))

Poster QMVislavicius.pdf

16:30 Untriggered di-hadron correlations in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with the ALICE experiment

We present measurements of untriggered di-hadron correlations in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV. The momentum evolution of untriggered data has been studied by applying symmetric $p_{\rm T}$ cuts. A smooth evolution of the structures in the correlation function is observed. We further quantify the evolution of the contributing components by fitting a model function. The model function quantifies possible initial state fluctuation contributions via the use of higher harmonics, $v_{n}$ ($n = 2, 3, 4, 5$). The near side jet peak is modeled with an asymmetric 2D Gaussian . In order to model non-flow contributions the Fourier harmonics are shown with and without such a 2D Gaussian. Extracted harmonics parameters are compared with IP Glasma model predictions.

Speaker: Danthasinghe Piyarathna (University of Houston (US))

Slides QM_2014Poster_v20.pdf

16:30 Upgrade STAR as a possible EIC detector

An Electron Ion Collider (EIC) is being considered as the next generation QCD facility to understand the fundamental question that how the visible universe is built up. More specifically, the EIC will probe the low Bjorken-x domain where gluons and sea quarks dominate with unprecedented precision, for both nucleon and nuclei. A possible realization of the accelerator facility based on the (currently operating) Relativistic Heavy Ion Collier (RHIC), called eRHIC, is proposed. The STAR detector, as one of the two major experiments at RHIC, has planned to evolve itself to eSTAR with a suite of upgrades optimized for EIC physics programs. The major components of the baseline upgrades will be introduced. The eSTAR detector performance and a broad range of deliverable measurements, which have been identified as the flagship science cases in an EIC, are demonstrated through simulation. An eSTAR has been found to be well suitable for an initial stage of eRHIC. References: 1. The EIC Whitepaper, The Electron Ion Collider: The Next QCD Frontier, http://arxiv.org/abs/1212.1701 2. eSTAR: The Letter of Intent, the STAR Collaboration, https://drupal.star.bnl.gov/STAR/starnotes/public/sn0592

Speaker: Ming Shao (Univ. of Sci. and Tech. of China)

Slides QM2014poster_v3.3.pdf

16:30 Upsilon production in U+U collisions at the STAR experiment

Due to color screening, the production of quarkonia in high energy heavy ion collisions is expected to be sensitive to the energy density of the medium. Sequential suppression of different quarkonium states may therefore serve as a thermometer of the medium. Although the suppression of charmonia was anticipated as a key signature of the QGP, the observed energy dependence of $J/\psi$ suppression is rather weak. This phenomenon is explained by the recombination (coalescence) of $c\bar{c}$ pairs. Bottomonia, on the other hand, are less affected by recombination and can provide a cleaner probe of the strongly interacting medium. Recent STAR results show that in $\sqrt{s_{NN}}=200$ GeV central Au+Au collisions the Upsilon 1S state is suppressed more than if only cold nuclear matter effects were present, and the excited state yields are consistent with a complete suppression. The energy density in U+U $\sqrt{s_{NN}}=193$ GeV central collisions is estimated to be about 20% higher than that of $\sqrt{s_{NN}}=200$ GeV central Au+Au. Therefore U+U collisions provide a further test of the sequential suppression hypothesis. The STAR detector collected a total of 17.2 million high-tower triggered events in $\sqrt{s_{NN}}=193$ GeV U+U collisions in the year 2012, corresponding to an integrated luminosity of 263.4 $\mu b^{-1}$. Upsilon yields at mid-rapidity, measured in central and mid-central collisions through the dielectron channel, as well as the nuclear modification factor with respect to the number of participants, will be reported in this presentation.

Speaker: Robert Vertesi (Nuclear Physics Institute of the Czech Academy of Sciences)

Poster UpsilonUU_vertesi_QM14-final.pdf

16:30 V0 Reconstruction in Au+Au-Collisions at 1.23 AGeV with HADES

In heavy ion collisions at beam energies of 1-2 AGeV, strangeness production can be observed below its elementary production threshold. In April and May 2012, 7.3 billion Au(1.23 GeV per nucleon)+Au collisions have been recorded by the HADES detector, installed at the Helmholtzzentrum fuer Schwerionenforschung (GSI) in Darmstadt, Germany. In this collision system the weakly decaying strange hadrons $K^{0}_{s}$ and $\Lambda$ were measured and can be reconstructed. In order to draw conclusions on strangeness production mechanisms in heavy ion collisions the yields can be compared to non-strange particle production, i.e. charged pions. In this contribution preliminary particle spectra of $\Lambda$ hyperons and $K^{0}_{s}$ mesons measured in these collisions are presented. Supported by BMBF (06FY9100I and 06FY7114), HIC for FAIR, EMMI, GSI, HGS-Hire and H-QM.

Speaker: Timo Scheib

16:30 Vorticity and asymmetries at NICA

Experimental manifestation of P-odd effects related to the vorticity and hydrodynamic helicity in non-central heavy ion collisions is discussed, which is based on their simulation in the NICA kinematics in framework of the kinetic Quark-Gluon String Model. For the NICA heavy ion collisions characterised by the large baryonic charge of the forming medium the effect should manifest in neutron asymmetries. The polarization of hyperons and P-odd correlations of particle momenta probing the vorticity are discussed.

Speaker: Prof. Alexander Sorin (Joint Institute for Nuclear Research (Dubna))

16:30 W boson production and the lepton charge asymmetry in lead-lead collisions in the ATLAS experiment

Lead-lead collisions at the LHC are capable of producing a system of deconfined quarks and gluons at unprecedented energy density and temperature. Partonic-level interactions and energy-loss mechanisms in the medium can be studied with the aid of useful probes. One of these probes are W bosons, which do not interact with the strongly-coupled medium and may be used to benchmark the energy loss of quarks and gluons produced in hard scattering events. Moreover, the W boson rapidity is directly sensitivity to nuclear parton distribution functions (nPDFs), thereby providing a handle on disentangling the free nucleon PDFs from nuclear PDFs. This study reports on W production yields identified via the electron and muon decay modes as a function of centrality and pseudorapidity in Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV with the ATLAS detector. The measurements from both channels are found to be consistent and were used to construct the lepton charge asymmetry.

Speaker: Rafal Bielski (AGH University of Science and Technology (PL))

Poster Bielski-R-poster.pdf

16:30 What can the event transverse energy distribution tell us about the longitudinal flow?

Transverse energy is an important characteristic of relativistic heavy ion collisions aiming at creating conditions similar to those existed in the early Universe. The hot and dense matter produced immediately after the collision of a nucleus going in the longitudinal direction and the other in the opposite direction can be considered as being composed of transverse fluid slices undergoing longitudinal expansion following the two receding nuclei. In the nucleon-nucleon center-of-mass frame, a slice that is closer to a nucleus has a bigger longitudinal speed. Transverse energy is longitudinally boost invariant and therefore directly reflects the condition of the local rest frame (slice) irrespective of its longitudinal flow speed. It is sensitive to the longitudinal work between adjacent slices and thus carries information about the evolution of the hot and dense matter produced in heavy ion collisions. We show that the work distribution of an expanding extreme relativistic gas is a gamma distribution with a different shape parameter as compared with its non-relativistic counterpart. This implies that the shape of the transverse energy distribution in relativistic heavy ion collisions depends on the particle contents during the evolution of the hot and dense matter. Therefore, transverse energy fluctuations provide additional insights into the Quark-Gluon Plasma produced in these collisions.

Speaker: Bin Zhang (Arkansas State University)

Poster QM14BinZhang2.pdf

16:30 When the heavy quark jet bends

We endeavour to explore the effect of recoil of heavy flavor jet due to scattering with light quarks. Earlier, neglecting this recoil we have observed a radiationless region along the direction of propagation of heavy quark jet, known as the dead cone. once we allow the heavy quark jet to bend, the dead-cone region is deluged by radiation. Hence this study, on one hand, is a step towards removing the prevalent eikonal approximation in jet-quenching models and on the other hand revisits the notion of dead-cone within the non-eikonal region.

Speaker: Surasree Mazumder (Variable Energy Cyclotron Centre, Kolkata)

Poster QM14_Poster_Trambak.pdf

16:30 Wigner Function on the lattice: a new tool to study the strongly coupled quark-gluon plasma at finite T and \mu

We study the temperature and chemical potential dependence of the momentum distributions of quasi-particles in the quark-gluon plasma. The Wigner functions of quarks and gluons, whose spatial integration is related to the momentum distributions, are calculated with the 2-flavor lattice QCD simulations. We found significant changes of the shape of the momentum distribution around the boundary between the hadronic phase and the quark-gluon plasma. This provides a new tool to study the behavior of the quasi-particles in the strongly coupled QGP.

Speaker: Yuji Sakai (Kyushu University)

16:30 Z Boson Production in p+Pb Collisions Measured by the ATLAS Experiment

The measurement of Z bosons in heavy ion collisions is an excellent tool for probing the nucleus at the partonic level. The inclusive yield provides a stringent test of binary collision scaling. Recent ATLAS results demonstrate such scaling in Pb+Pb collisions. The 2013 p+Pb physics run at the LHC providing more than 30 nb^-1 of collisions at an energy of sqrt(s_NN)=5.02 TeV has made a detailed study of Z boson production in proton+nucleus interactions possible for the first time. These data may confirm binary scaling in the p-Pb system and help clarify the present ambiguity of centrality classifications in proton+nucleus collisions. Further, the momentum and rapidity differential yields of Z bosons allow the detection of any modification of the initial state present in such collisions. The ATLAS experiment allows the analysis of Z boson production via the di-electron and di-muon channels over a wide acceptance in rapidity. We will present the Z boson yield measured by the ATLAS experiment in p+Pb collisions at the LHC.

Speaker: Zvi Citron (Weizmann Institute of Science (IL))

Wednesday 21 May

09:00 → 10:40 Correlations and fluctuations: 3

Convener: Jurgen Schukraft (CERN)

announcement QM2014_announcement_Wed.pdf

09:00 Multi-Particle production and ridge structure in A+A, p+A, and p+p collisions

The IP-Glasma initial state model [1,2] coupled to relativistic viscous fluid dynamics successfully describes particle spectra, anisotropic flow, and its fluctuations in central to mid-central heavy-ion collisions [3]. Here we extend the study to more peripheral events and determine if the description remains robust. We then perform a direct comparison of peripheral A+A events with p+A and p+p events in the same multiplicity bins. Ridge-like correlations from the initial glasma state can also be computed in the IP-Glasma framework. We analyze their contribution which can be strong in small systems but is reduced in heavy-ion collisions. [1] B. Schenke, P. Tribedy, R. Venugopalan, Phys. Rev. Lett. 108, 252301 (2012) [2] B. Schenke, P. Tribedy, R. Venugopalan, Phys. Rev. C89, 024901 (2014) [3] C. Gale, S. Jeon, B. Schenke, P. Tribedy, R. Venugopalan, Phys. Rev. Lett. 110, 012302 (2013).

Speaker: Dr Bjoern Schenke (Brookhaven National Lab)

Slides SCHENKE-QM2014.pdf

09:20 Signatures of collective behavior in small systems

We perform 3+1D viscous hydrodynamic calculations of proton-nucleus and nucleus-nucleus collisions. The goal is to ascertain the nature of the striking correlations seen in recent proton-nucleus collisions. In particular, one would like to know: is the observed ridge a signature of collective behavior? Can the highest multiplicity collision systems be accurately described as a relativistic fluid? If so, at what point does hydrodynamics fail to describe the bulk evolution? To this end, we propose to measure the detailed transverse momentum structure of two-particle correlations. They must satisfy rigid inequality relations in any hydrodynamic system, and within those bounds we show that they should have a particular dependence on multiplicity over the entire measured centrality range. Any deviation from this behavior would signal a breakdown of a hydrodynamic description. We also show how a simultaneous description of Pb-Pb and p-Pb data can put a significant constraint on theoretical models. Finally, we compare our calculations to the full set of existing measurements, demonstrating what parameters are required for a good fit to data and commenting on what can be learned.

Speaker: Igor Kozlov (McGill University)

Slides Kozlov_21_05_14_9am20.pdf

09:40 Causal baryon diffusion and colored noise

We construct a model of baryon diffusion which has the desired properties of causality and analyticity. The model also has the desired property of colored noise, meaning that the noise correlation function is not a Dirac delta function in space and time; rather, it depends on multiple time and length constants. The model can readily be incorporated in 3+1 dimensional 2nd order viscous hydro-dynamical models of heavy ion collisions, which is particularly important at beam energies where the baryon density is large.

Speaker: Prof. Joseph Kapusta (University of Minnesota)

Slides Kapusta_QM2014.pptx

10:00 What the collective flow excitation function can tell about the quark-gluon plasma

The midrapidity slope d$v_1$/d$y$ of the directed flow $v_1$ has been predicted to be sensitive to the possible first-order phase transition between the hadron gas and the quark-gluon plasma. The recent STAR data from the RHIC beam energy scan (BES) show that the net-proton d$v_1$/d$y$ changes sign twice within the collision energy range 7.7 - 39 GeV. To further investigate this phenomenon, we study the collision energy dependence of $v_1$ utilizing a Boltzmann + hydrodynamics hybrid model. Such a hybrid approach provides a natural framework for the transition from high collision energies, where the hydrodynamical description is essential, to smaller energies, where the hadron transport dominates. Calculation with dynamically evolved initial and final state shows no qualitative difference between an equation of state with cross-over and one with first-order phase transition [1], in contrast to the earlier pure fluid predictions. We have also investigated the energy evolution of the elliptic flow $v_2$ and triangular flow $v_3$ [2]. The $v_2$ analysis shows that pre-equilibrium transport dynamics are partially compensating for the diminished elliptic flow production in the hydrodynamical phase at lower energies, resulting to relatively weak collision energy dependence which is in qualitative agreement with STAR BES results. The medium described by transport is, however, too viscous to build up triangular flow, making $v_3$ the clearer signal for the formation of (near-)ideal fluid in relativistic heavy ion collisions. References: [1] J. Steinheimer, J. Auvinen, H. Petersen, M. Bleicher and H. Stocker, work in progress; [2] J. Auvinen and H. Petersen, Phys. Rev. C88, 064908 (2013).

Speaker: Dr Jussi Auvinen (Frankfurt Institute for Advanced Studies)

Slides auvinen_QM2014.pdf

10:20 Differential HBT method to analyse rotation in heavy ion collisions

With increasing beam energies the angular momentum of the fireball in peripheral heavy ion collisions is increasing. The earlier predicted rotation effect and Kelvin Helmholtz Instability, leads to space-time momentum correlations among the emitted particles. For these reactions two particle correlations are studied. A specific combination of two particle correlation measurements is proposed, the Differential Hanbury Brown and Twiss method, which can sensitively detect the rotation of the emitting system. In case of azimuthally symmetric systems without rotation the new method gives zero signal, while it is sensitive to the rotation in the system. The method is studied in simple models and in numerical fluid dynamic model results. The talk is based on recent results and the following publications: [1] L.P. Csernai, D.D.Strottman and C. Anderlik, Phys. Rev. C 85, 054901 (2012). [2] L.P. Csernai, V.K. Magas and D.J. Wang, Phys. Rev. C 87, 034906 (2013). [3] L.P. Csernai, S. Velle, (2013) arXiv:1305.0385 [4] L.P. Csernai, S. Velle and D.J. Wang, arXiv:1305.0396

Speaker: Laszlo Csernai (Department of Physics and Technology)

Slides 1-Csernai-QM-2014-May.ppt

09:00 → 10:40 Thermodynamics and hadron chemistry

Convener: Christina Markert (University of Texas (US))

announcement QM2014_announcement_Wed.pdf

09:00 Multi-strange baryon production in pp, p-Pb and Pb-Pb collisions measured with ALICE at the LHC

Multi-strange baryons are of particular interest in the understanding of particle production mechanisms, as their high strangeness content makes them more susceptible to changes in the hadrochemistry of the colliding systems. In this talk, $\Xi$ and $\Omega$ production rates measured with ALICE are reported as a function of $p_{\mathrm{T}}$ in proton-proton (pp), proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions. Multi-strange baryons were reconstructed via the detection of their weak decay products, which were identified through their measured energy loss and momenta in the ALICE Time Projection Chamber. For p-Pb and Pb-Pb, the $\Xi$ and $\Omega$ spectra were analysed as a function of charged particle multiplicities, which range over several orders of magnitude. In the p-Pb system in particular, it is possible to investigate a multiplicity region in which relative strangeness production changes significantly, as seen when comparing peripheral Pb-Pb to pp collisions. In order to investigate the phenomenon of strangeness enhancement, we study how the singly-strange and multi-strange baryon production relative to non-strange particles evolves with multiplicity. Finally, the results from these various colliding systems are also compared to each other as well as to Monte Carlo predictions.

Speaker: Didier Alexandre (University of Birmingham (GB))

Slides QM14-DAlexandre.pdf

09:20 $\Omega$ and $\phi$ production in p+p, Au+Au and U+U collisions at STAR

Multi-strange hadrons are excellent probe to the hadronization of the hot and dense medium produced in heavy ion collisions, since they may decouple earlier from the hadronic system. The STAR measurements of $\Omega$ to $\phi$ ratio and $\Omega$, $\phi$ nuclear modification factors at intermediate $p_{\rm T}$ at top RHIC energies are consistent with expectations from recombination/coalescence models, which assume a seemingly thermalized partonic medium created at RHIC. However, the limited statistics put large uncertainties in those measurements. The high-statistics p+p, Au+Au and U+U data collected by STAR during the years of 2011 and 2012 will enable a high-precision systematic survey of these observables. Comparing data from Au+Au and U+U collisions also allows us to identify possible different medium properties due to different system size. In this talk, we present the measurements of $\Omega$ and $\phi$ production in $\sqrt{s}$ = 200 GeV p+p, $\sqrt{s_{NN}}$ = 200 GeV Au+Au, 193 GeV U+U collisions. The $\Omega$, $\phi$ nuclear modification factors and $\Omega$ to $\phi$ ratios will be presented for both Au+Au and U+U up to $p_{T} \sim$ 6 GeV/$c$. Strangeness enhancement factors for $\Omega$ and $\phi$ in U+U, Au+Au with respect to p+p collisions will be presented as well. Implications on collision dynamics will be discussed.

Speaker: Xianglei Zhu (Tsinghua University)

Slides zhu_qm2014_v12.pdf

09:40 Light (Hyper-)Nuclei production at the LHC measured with ALICE

The high collision energies reached at the LHC lead to significant production yields of light (hyper-)nuclei in proton-proton, proton-lead and, in particular, lead-lead collisions. The excellent particle identification capabilities of the ALICE apparatus, based on the specific energy loss in the time projection chamber and the velocity information in the time-of-flight detector, allow for the detection of these rarely produced particles. Furthermore, the inner tracking system gives the possibility to separate primary nuclei from those coming from the decay of heavier systems. One example is the hypertriton ($^3_{\Lambda}$H $\rightarrow ^3$He + $\pi^-$) another one is the possible decay of a hypothetical bound state of a $\Lambda$ with a neutron decaying into deuteron and pion. We present results on the production of stable nuclei and anti-nuclei in Pb--Pb and lighter collision systems. 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. All results are compared with predictions for the production in thermal (statistical) models and alternatives using coalescence.

Speaker: Nicole Alice Martin (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

Slides QM2014_Nuclei_Presentation_Nicole_Martin.pdf

10:00 Understanding the $p/\pi$ ratio at LHC with an extended mass spectrum

Recent measurements of the proton to pion ratio from ALICE at the LHC have found it to be lower than the expected ratio anticipated by thermal models. We investigated the role that Hagedorn states- massive resonances with an exponential mass spectrum and large decay widths- play in the determination of particle ratios at LHC through a scenario of multiparticle reactions and dynamical chemical equilibrium within the hadron gas phase. We show that it is possible to describe the lower $p/\pi$ ratio at LHC while still obtaining the experimental ratio of $K/\pi$ in the Hagedorn state scenario if the protons are underpopulated at the switching temperature from hydrodynamics to the hadron gas phase.

Speaker: Dr Jacquelyn Noronha-Hostler (University of Sao Paulo)

Slides jnoronhahostler.pdf

10:20 Systematics of the kinetic freeze-out properties in high-energy nuclear collisions from STAR

The main aim of the RHIC Beam Energy Scan (BES) program is to explore the QCD phase diagram which includes search for a possible QCD critical point and the phase boundary between QGP and hadronic phase. We report the collision energy and centrality dependence of kinetic freeze-out properties from the measured mid-rapidity light hadrons (pions, kaons, protons and their anti-particles) for Au+Au collisions at the center-of-mass energy root(s_nn) = 7.7, 11.5, 19.6, 27, and 39 GeV. The STAR detector, with a large uniform acceptance and excellent particle identification is used in the data taking. The kinetic freeze-out temperature (T_fo) and average collective velocity (beta) parameters are extracted from blast-wave fits to the identified hadron spectra and systematically compared with the results from other collision energies including those at AGS, SPS and LHC. It is found that all results fall into a correlation band in the 2-dimension (T_fo, beta) distribution: the largest value of collective velocity and lowest temperature is reached in the most central collisions at the highest collision energy. We study the energy dependence of these freeze-out parameters and implications of the systematics as a function of beam energy are also explored for particle and antiparticle separately.

Speaker: Lokesh Kumar (National Institution of Science Education and Research)

Slides Lokesh_QM2014.pdf

09:00 → 10:40 Jets: 4

Convener: Rene Bellwied (University of Houston (US))

announcement QM2014_announcement_Wed.pdf

09:00 Jet-track correlation in PbPb collisions with CMS

A strong modification of jet properties has been observed in central PbPb collisions when compared to the results from pp collisions. To characterize the energy flow, we present the first detailed measurement of the energy flow of quenched jets with the CMS detector. Those new results extend previous measurements to large angle with respect to the quenched jets, using the high statistics pp and PbPb data taken in 2011-13. Jet shapes, fragmentation functions and missing transverse momenta are studied by correlating jets and tracks as a function of centrality and dijet asymmetry.

Speaker: Doga Can Gulhan (Massachusetts Inst. of Technology (US))

Slides doga_QM2014.pdf

09:20 Angular correlations of jets in lead-lead collisions at 2.76 TeV using the ATLAS detector at LHC

Highly energetic jets produced in nuclear collisions are considered to be a direct probe of hot and dense medium created in the collision. The jet measurements both at LHC and RHIC indicate a presence of "jet quenching" - strong energy loss of fast partons in the hot and dense QCD medium. This talk presents study of properties of the multi-jet production in heavy ion collisions presented in terms of jet angular correlations. The jet angular correlations are valuable tool to study the beyond leading order effects in QCD and are expected to shade a new light on the process of the energy loss. The analysis is performed using Pb+Pb data collected in 2011 by the ATLAS detector at the center of mass energy of 2.76 TeV.

Speaker: Martin Rybar (Charles University (CZ))

Slides QM2014_Rybar.pdf

09:40 Semi-inclusive recoil jet distribution and di-jets imbalance measurements in central Au+Au collisions in STAR

The measurement of fully reconstructed jets in heavy ion collisions provides unique probes of the Quark-Gluon Plasma (QGP). However, full jet reconstruction in such events is challenging due to a large population of combinatorial background "jets" that overwhelm the true hard jet population by several orders of magnitude. In order to carry out accurate, data-driven jet measurements over a broad kinematic range at RHIC energies, we developed a novel mixed-event technique that describes the combinatorial jet background over several orders of magnitude with high precision. We apply this technique to measure the semi-inclusive charged jet distribution recoiling from a high $p_{T}$ hadron trigger in central Au+Au collisions at $\sqrt{s_{NN}}=$200 GeV. We report the recoil jet distribution for various trigger $p_{T}$ ranges and jet radii, and study the azimuthal distribution between the recoil jet and trigger hadron. In addition we present the first measurement at RHIC of the di-jet transverse momentum asymmetry, $A_J$. Both measurements are performed with a very low infrared cutoff on jet constituents of 200 MeV. These jet coincidence measurements allow a direct comparison of jet quenching at RHIC and the LHC.

Speaker: Joern Putschke (Wayne State University)

Slides qm14_star_dijet_putschke.pdf

10:00 Jet propagation within a Linearized Boltzmann Transport Model

A Linearized Boltzmann Transport model is developed for the study of parton propagation inside quark-gluon plasma. The leading partons, thermal recoiled partons and radiated gluons are all tracked so that one can also study jet-induced medium excitation. In this study, we implement the complete set of elastic parton scattering processes and investigate parton energy loss, transverse momentum broadening and their nontrivial energy and length dependence. We further investigate the jet shape and fragmentation functions of reconstructed jets using FASTJET algorithm. Contributions from the recoiled thermal partons are found to have significant influences on jet shape and angular distribution of reconstructed jets.

Speaker: Mr Tan Luo (Central China Normal University)

Slides QM2014-LuoTan.pdf

10:20 Studies of dijet and photon-jet properties in pp, pPb and PbPb collisions with CMS

Studies of dijet and photon-jet properties in pPb collisions are of great importance to establish a QCD baseline for hadronic interactions with cold nuclear matter. Dijet and photon-jet production have been measured in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The transverse momentum balance and azimuthal angle correlations are studied in both dijet and photon-jet channels, leading to the observation that there is no significant modification, which allows these systems to be used as tools to probe the nuclear modifications of the parton distribution functions (PDFs). In the dijet system, pseudorapidity distributions are studied as a function of the transverse energy in the forward calorimeters (${\rm E_T}^{HF}$). The mean value of the dijet pseudorapidity is found to change monotonically with increasing $\mathrm{E}_\mathrm{T}^{HF}$, indicating a correlation between the energy emitted at large pseudorapidity and the longitudinal motion of the dijet frame. The pseudorapidity distribution of the dijet system is compared with next-to-leading-order perturbative QCD predictions obtained from both nucleon and nuclear PDFs, and the data more closely match the latter. In addition to the studies of initial state, the photon-jet measurements related to quenching in PbPb are updated to have a more precise pp reference based on the 2013 LHC run at 2.76 TeV.

Speaker: Richard Alexander Barbieri (Massachusetts Inst. of Technology (US))

Slides 2014-05-09-QM2014-alex_v4.pdf

09:00 → 10:40 Heavy flavor: 6

Convener: Mihai Petrovici (National Institute for Physics and Nuclear Engineering (IFIN-HH))

announcement QM2014_announcement_Wed.pdf

09:00 $J/\psi$ and Upsilon nuclear modification in A$+$A collisions

PHENIX presents new nuclear modification results on $J/\psi$ in Cu$+$Au and U$+$U collisions. The recently completed analysis of the modification of $J/\psi$ production in Cu$+$Au collisions at forward ($1.2< y < 2.2$) and backward ($-2.2 < y < -1.2$) rapidity is the first measurement of the rapidity dependence of the $J/\psi$ modification in unequal mass heavy ion collisions. Both hot and cold nuclear matter effects are expected to be asymmetric in rapidity in these collisions. The comparison of $d$$+$Au, Au$+$Au, U$+$U and Cu$+$Au $J/\psi$ modifications across rapidities provides insight on the balance of cold and hot nuclear matter effects. We also present new PHENIX centrality results on $\Upsilon$(1S$+$2S$+$3S) production in p$+$p and Au$+$Au collisions. These results indicate significant suppression of the $2S$ and $3S$ states in the Quark-Gluon Plasma (QGP) environment. The results on temperature dependent heavy quarkonia production and evolution in the medium have the potential to bracket the temperature of the QGP.

Speaker: Cesar Luiz da Silva (Los Alamos National Lab)

Slides QM2014_quarkonia_PHENIX.pptx QM2014_quarkonia_PHENIX_v2.pdf

09:20 Production of J/psi and Y-mesons in proton-lead collisions at √sNN = 5 TeV

The production of J/psi and Y-mesons decaying into dimuon final state is studied at the LHCb experiment, with rapidity 1.5 < y < 4.0 or −5.0 < y < −2.5 and transverse momentum $p_T$ < 15 GeV/c, in proton-lead collisions at a proton-nucleon centre-of-mass energy $\sqrt{s_{NN}}$ = 5 TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 1.6 nb$^{−1}$. The forward-backward production ratio and the nuclear modification factor are determined for J/psi and Y(1S). Indication of forward backward production asymmetry is observed. There is also an indication of J/psi and Y(1S) production suppression with respect to proton-proton collisions in forward region and anti-shadowing effect in backward region.

Speaker: Zhenwei Yang (Tsinghua University (CN))

Slides QM2014_lhcb.pdf

09:40 Bottomonia in pp, pPb and PbPb with CMS

Bottomonia are important probes of the quark-gluon plasma since they are produced at early times and propagate through the medium, mapping its evolution. The three Y states (1S, 2S, 3S) were measured separately using the Compact Muon Solenoid (CMS) experimental apparatus and observed to disappear sequentially in PbPb collisions at 2.76 TeV. However, recent measurements in pp and pPb collisions, at 2.76 and 5.02 TeV respectively, show a surprising dependence of the excited (2S or 3S) over the ground (1S) state ratio, as a function of the global event activity. The three states are also observed to be individually more produced in events with more activity, for the three collision systems. In this talk, we will review the latest results from pp, pPb and PbPb collisions and highlight their possible interpretations.

Speaker: Abdulla Abdulsalam Valiyavalappil Kizhakkepura (Bhabha Atomic Research Centre (IN))

Slides Bottomonia_Abdulla_QM14_v4.pdf

10:00 $\Upsilon$ production in hadronic collisions with ALICE at the LHC

ALICE is the LHC experiment devoted to the study of heavy-ion collisions. The main purpose of ALICE is to investigate the properties of the deconfined state of nuclear matter, the Quark-Gluon Plasma (QGP). Quarkonium measurements play a crucial role in this investigation. In particular, the sequential suppression of the quarkonium states by colour screening has long been suggested as a signature and thermometer of the QGP. The first results on quarkonium suppression in Pb-Pb collisions at the LHC seem to indicate that for charmonia both regeneration and colour screening mechanisms play a role while for bottomonia the regeneration mechanism should be small. Initial state effects can play a role in bottomonium production in Pb-Pb collisions and thus should be studied using proton-nucleus collisions, where no deconfined state is expected to be created. $\Upsilon$ production can be measured in ALICE in the dimuon decay channel using the forward muon spectrometer. We will present the latest results on $\Upsilon$ production in pp, p-Pb and Pb-Pb collisions at LHC energies measured by the ALICE experiment at forward-rapidity.

Speaker: Javier Castillo Castellanos (CEA/IRFU,Centre d'etude de Saclay Gif-sur-Yvette (FR))

Slides upsilonQM0514.pdf

10:20 Upsilon production as a probe of the early state in heavy ion collisions

Upsilon production in heavy ion collisions at RHIC and LHC is investigated. While the transverse momentum spectra of the ground state Upsilon(1s) are controlled by the initial state Cronin effect, the excited states are characterized by the competition between the cold and hot nuclear matter effects and sensitive to the dissociation temperatures determined by the heavy quark potential. We emphasize that it is necessary to measure the excited heavy quark states in order to extract the early stage information in high energy nuclear collisions.

Speaker: Prof. Pengfei Zhuang (Tsinghua University)

Slides QM2014_Zhuang.pdf

10:40 → 11:10 Coffee break

11:10 → 13:30 Future experimental facilities, upgrades, and instrumentation

Convener: Sibaji Raha (Bose Institute (IN))

announcement QM2014_announcement_Wed.pdf

11:10 Status of the FAIR Accelerators

In 2018, a broad spectrum of unprecedented fore-front research becomes available at the Facility for Antiproton and Ion Research, FAIR. The new facility is being constructed within the next five years adjacent to the existing accelerator complex of the GSI Helmholtz Centre for Heavy Ion Research at Darmstadt/Germany. It will deliver stable and rare isotope beams covering a huge range of intensities and beam energies. The challenges are heavy ion synchrotrons for highest intensities, antiproton and rare isotope production stations, high resolution separators and several storage rings where beam cooling can be applied. Here new kind of superconducting magnets, rf-systems, injection and extraction systems and beam diagnostics will be applied. As the construction of the FAIR facility and procurement has started, an overview of the designs, procurements status and infrastructure preparation will be provided.

Speaker: Dr Udo Weinrich (GSI)

Slides QM2014_ID649_FAIR_Accelerators_UW.pdf

11:30 Measurement of rare probes with the Silicon Tracking System of the CBM experiment at FAIR

The Compressed Baryonic Matter experiment at FAIR will explore the phase diagram of strongly interacting matter at highest net baryon densities and moderate temperatures. The CBM physics program will be started with beams delivered by the SIS 100 synchrotron, providing energies from 2 to 11 GeV/nucleon for heavy nuclei, up to 14 GeV/nucleon for light nuclei, and 29 GeV for protons. The highest net baryon densities will be explored with ion beams up to 45 GeV/nucleon energy delivered by SIS 300 in the next stage of FAIR. Collision rates up to 10$^7$ per second are required to produce very rare probes with unprecedented statistics in this energy range. Their signatures are complex. These conditions call for detector systems designed to meet the extreme requirements in terms of rate capability, momentum and spatial resolution, and a novel DAQ and trigger concept which is not limited by latency but by throughput. In the presentation we describe the concepts of CBM’s central detector, the Silicon Tracking System, and of the First-Level Event Selector, a dedicated computing farm to reduce on-line the raw data volume by up to three orders of magnitude to a recordable rate. Progress with the development of detector and software algorithms are discussed and examples of performance studies on the reconstruction of rare probes at SIS 100 and SIS 300 energies given.

Speaker: Dr Johann Heuser (GSI)

Slides J.Heuser_CBM_QM2014.pdf J.Heuser_CBM_QM2014.pptx

11:50 The STAR Heavy Flavor Tracker

In relativistic heavy-ion collisions at RHIC, heavy quarks are primarily created from initial hard scatterings. Due to the heavy masses, their intrinsic properties are much less affected by the QCD medium compared to those of light quarks. Therefore heavy quark hadrons are suggested as a clean probe for the studying of early dynamic evolution of the dense and hot medium created in high-energy nuclear collisions. To enhance the study of heavy quark production at RHIC, the Heavy Flavor Tracker (HFT) for the STAR experiment has been built and installed before RHIC Run 14. The HFT consists of four layers of silicon detectors. The two outermost layers are silicon strip detectors and the two innermost layers are made from the state of art ultra thin CMOS Monolithic Active Pixel Sensors (MAPS). This is the first application of the CMOS MAPS detector in a collider experiment. The thin pixel sensors plus the carbon fiber supporting design reduces the material to 0.4 % radiation length per pixel detector layer, enabling reconstruction of low pT heavy flavor hadrons. In this talk, the status and performance of HFT in the current 200 GeV Au+Au run will be discussed.

Speaker: Dr Hao Qiu (LBNL)

Slides StarHeavyFlavorTracker.pdf

12:10 The upgrade of the ALICE Inner Tracking System

The long term plan of ALICE (A Large Ion Collider Experiment) is a detailed investigation and characterization of the Quark-Gluon Plasma (QGP) in order to fully exploit the scientific potential of the LHC with heavy ions at high luminosity after the Long Shutdown 2 (LS2) scheduled in 2018-2019. The study will focus on high precision measurements of rare probes over a wide range of momenta, which would require high statistics and are not satisfactory or even possible with the present experimental set up. To improve its physics capabilities, ALICE has formulated an upgrade strategy of several detectors to be installed during LS2 under the assumption that the LHC will progressively increase its luminosity with Pb beams eventually reaching an interaction rate of about 50 kHz. Within this upgrade strategy, the Inner Tracking System (ITS) upgrade forms an important cornerstone, providing precise measurements for heavy-flavour interactions with the QGP medium and for the production of thermal photons and low-mass dileptons by highly improved tracking and vertexing capabilities. These new measurements would provide an insight to the study of, in particular, the thermalization of heavy quarks in the QGP and the in-medium energy loss, and to assess the initial temperature and degrees of freedom of the system, respectively. The new ITS has a barrel geometry consisting of seven layers of Monolithic Active Pixel Sensors (MAPS) with high granularity, which would fulfil the material budget, readout and radiation hardness requirements for the upgrade. The layout and the properties of the new ITS are optimized for high tracking efficiency, both standalone and in combination with the outer Time Projection Chamber (TPC). In this contribution, the performance of the new ITS will be presented and compared to the current setup. An overview of the technical developments for the detector elements and of the construction procedures will also be presented.

Speaker: Sabyasachi Siddhanta (Universita e INFN (IT))

Slides QM2014_Siddhanta.pdf

12:30 Future upgrade and physics perspectives of the ALICE TPC

The Time Projection Chamber (TPC) is one of the main tracking and PID devices in the central barrel of the ALICE detector at the CERN Large Hadron Collider. It provides precise charged-particle tracking, momentum measurement, and particle identification in very high multiplicity heavy-ion collisions. The readout rate of the TPC is currently limited by the necessity to prevent ions from the amplification region of the MWPC-based readout chambers to drift back into the drift volume, which is achieved through active ion gating by operating a dedicated Gating Grid. The relevant ion drift times limit the maximum trigger rate of the TPC to about 3.5 kHz. In order to make full use of the increase in luminosity after the second long shutdown of the LHC, it is foreseen to operate the detector in an ungated mode with continuous readout. Therefore the existing MWPC readout will be replaced by a Gas Electron Multiplier (GEM) readout, which provides intrinsic ion capture capability without additional gating. Furthermore, new readout electronics will be implemented to match the requirements of continuous readout with GEMs. Together with advanced techniques for online space-charge corrections, the upgrade will enable the detector to perform to specifications at collision rates of up tp 50 kHz foreseen for the LHC Pb-Pb program in RUN 3. After the upgrade of the TPC, the data collection rate of the TPC in Pb-Pb will be increased by about a factor 100 as compared to the present system, which will enable improved measurements to understand heavy quark and quarkonium production, low-mass dielectron production, jets and jet correlations, and the production of exotic hadrons. In this talk, the expected physics performance and status of the extensive R&D program to reach this ambitious goal will be presented.

Speaker: Taku Gunji (University of Tokyo (JP))

Slides gunji_alice_upgrade_v2_3.pdf gunji_alice_upgrade_v2_3.pptx

12:50 Towards the heavy-ion program at J-PARC

J-PARC is going to achieve its designed proton beam power of 0.75 MW at 30 GeV for neutrino physics and 1 MW at 3 GeV for material and life sciences in several years. Recently, discussions of heavy ion acceleration as the future J-PARC project have been held among nuclear physicists and accelerator scientists. The main goals of the program are to explore the QCD phase diagram at high baryon density with the heaviest ions such as uranium at the beam energies of around 10 AGeV. We are planning to focus on the electron and muon measurements and rare probe search such as multi-strangeness and charmed hadrons by taking advantage of the world's highest beam power available at J-PARC, in addition to identified hadron measurements in large acceptance. A heavy-ion acceleration scheme has been considered with a new heavy-ion linac and a new booster ring, which accelerate and inject heavy-ion beams into the existing 3-GeV Rapid-Cycling Synchrotron, and the 30-GeV Main Ring synchrotron. We present the overview of the heavy-ion program and accelerator design, as well as physics goals and conceptual design of the heavy-ion experiments.

Speaker: Hiroyuki Sako (Japan Atomic Research Agency)

Slides QM14-JPARCHI-sako.pdf QM14-JPARCHI-sako.pptx

13:10 Heavy-ion physics studies for the Future Circular Collider

A five-year international design study called Future Circular Collider (FCC) has been launched by CERN with a kick-off meeting in February 2014. The main goal is a hadron collider with a centre-of-mass energy of the order of 100 TeV for pp collisions in a new 80-100 km tunnel in the Geneva area. The target start of operation would be 2035-40. Operating such machine with heavy ions is an option that is being considered in the accelerator design studies. It would provide, for example, Pb-Pb and p-Pb collisions at $\sqrt{s_{\rm NN}}=39$ and 63 TeV, respectively, with monthly integrated luminosities of the order of 5-10/nb. We will present first ideas on the physics opportunities with heavy ions at the FCC. The Quark-Gluon Plasma (QGP) state produced in Pb-Pb collisions at 39~TeV is expected to have initial temperature and energy density substantially larger than at LHC energy, a stronger flow field and freeze-out volume twice as large. The larger temperature could entail novel features, like changes in the quarkonium spectrum and abundant in-medium production of charm quarks. The latter could determine an increase in the number of degrees of freedom (from 3 to 4 quark flavours). The larger energy and luminosities will make new, rarer, hard probes available (like top quarks and $Z+Jets$), which could give access to the time-evolution of the medium properties, e.g. of its opacity. In the sector of small-$x$ and saturation physics, the increase in centre-of-mass energy of a factor seven with respect to the LHC will extend the kinematic coverage in $x$ and $Q^2$, providing, with pA and $\gamma$A (ultra-peripheral collisions), access to the saturation region down to $x< 10^{-6}$ with perturbative probes like heavy quarks and quarkonia. High-density or collective effects in high-multiplicity pp and pA events could become more dramatic, with the increase of energy and high-multiplicity reach. Opportunities for electroweak physics studies in UPC gamma-gamma collisions, as well as the impact of heavy-ion data at the FCC for ultra-high energy cosmic-ray physics, will also be summarized.

Speaker: Andrea Dainese (INFN - Padova (IT))

Slides Dainese_FCC_QM14_v1.pdf

11:10 → 13:30 Correlations and fluctuations: 4

Convener: Dr Alberica Toia (Johann-Wolfgang-Goethe Univ. (DE))

announcement QM2014_announcement_Wed.pdf

11:10 Bose-Einstein correlation measurements at CMS

Multidimensional and one-dimensional quantum-statistical (Bose-Einstein) correlations are measured in proton-proton collisions at 0.9, 2.76 and 7 TeV, and in proton-lead collisions at 5.02 TeV/nucleon pair center-of-mass energy with the CMS detector at the LHC. The correlation functions are extracted in terms of different components of the relative momentum of the pair, in order to investigate the extension of the emission source in different directions. The results are presented for different intervals of transverse pair momentum, $k_T$, and charged particle multiplicity of the collision, $N_{ch}$, as well as for their integrated values. Besides inclusive charged particles, charged pions and kaons, identified via their energy loss in the silicon tracker detector, can also be correlated. The extracted source radii are reaching the highest values for very high multiplicity pPb collisions, and decrease with increasing $k_T$. The results open the possibility to study scaling and factorization properties of these radii as a function of multiplicity, $k_T$, colliding system size and center-of-mass energy.

Speaker: Sunil Manohar Dogra (UNESP - Universidade Estadual Paulista (BR))

Slides SDogra_QM2014.pdf

11:30 Freeze-out radii extracted using two- and three-pion Bose-Einstein correlations in pp, p-Pb, and Pb-Pb collisions at the LHC

Two-pion Bose-Einstein correlations are often used to extract the radius of the particle emitting source at freeze-out. The extraction of the radii in low multiplicity systems is complicated by the presence of background correlations such as mini-jets. Such backgrounds can be suppressed through the use of three-pion cumulant correlations. We present two- and three-pion Bose-Einstein correlations in pp, p-Pb, and Pb-Pb collisions with ALICE at the LHC. The extracted freeze-out radii are compared in all three systems at similar multiplicity. The results are discussed in view of initial and final state effects.

Speaker: Dhevan Raja Gangadharan (Lawrence Berkeley National Lab. (US))

Slides QM2014_Dhevan.pdf

11:50 Femtoscopic pair correlations of mesons and baryons at RHIC and LHC from hydrokinetic model

The femtoscopic scales for identical pions and kaons are presented at different centralities for the top energy RHIC and LHC A+A collisions in comparison with ones for p+p collisions. The later results are obtained in hydrokinetic model (HKM) in view of the quantum uncertainty principle. The three-dimensional pion and kaon emission source functions are extracted from the HKM model simulations for A+A collisions. The model describes well the experimental data, previously obtained by the PHENIX and STAR collaborations using the imaging technique. In particular, the HKM reproduces the non-Gaussian heavy tails of the source function in the pair transverse momentum (out ) and beam (long) directions, observed in the pion case and practically absent for kaons. The role of the rescatterings and long-lived resonances decays in forming of the long range tails is investigated. The prediction is made for the source functions in the LHC Pb+Pb collisions at √s= 2.76 TeV. As for the baryon-baryon correlations, the source functions of pp, pΛ and p ̅Λ pairs are found in Au+Au collisions and used by means of FSI correlation technique for an extraction of the scattering lengths in two-baryon systems. The role of residual correlations in formation of the total baryon-baryon correlation function is analyzed. The talk is based on the results of the following works: 1. Iu.A. Karpenko, Yu.M. Sinyukov. Uniform description of bulk observables in the hydrokinetic model of A+A collisions at RHIC and LHC, Phys. Rev. C 87, 024914 (2013). 2. V.M. Shapoval, P. Braun-Munzinger, Iu.A. Karpenko, Yu.M. Sinyukov. Femtoscopic scales in p+p and p+Pb collisions in view of the uncertainty principle. Phys. Lett. B 725, 139 (2013). 3. V.M. Shapoval, Yu.M. Sinyukov, Iu.A. Karpenko. Emission source functions in heavy ion collisions, Phys. Rev C 88 064904 (2013). 4. V. M. Shapoval, B. Erazmus, R. Lednicky, and Yu. M. Sinyukov. Extracting pΛ and p ̅Λ scattering lengths from heavy ion collisions. Proceedings of the International School-Seminar “New Physics and Quantum Chromodynamics at External Conditions", pp. 115-119 , 2013, Dnipropetrovsk, Ukraine. (Publication in preparation). 5. V.M. Shapoval, P. Braun-Munzinger, Iu.A. Karpenko, Yu.M. Sinyukov. Femtoscopic correlations of kaons in Pb+Pb and p+p collisions at LHC within hydrokinetic model. (Publication in preparation).

Speaker: Prof. Yuri Sinyukov (Bogolyubov Institute for Theoretical Physics)

Slides QM-2014-Sinyukov.pdf

12:10 Emission angle and particle mass dependence of HBT Interferometry in Au$+$Au collisions at $\sqrt{s_{NN}} = 200$ GeV

The initial density distribution in a heavy ion collision fluctuates due to the finite number of participating nucleons, which leads to higher harmonic flow as recently measured at RHIC and the LHC. Such spatial fluctuations may be preserved until kinetic freeze-out, depending on the strength of the initial fluctuations, the flow profile, the expansion time, and viscosity of the created matter. Hanbury Brown and Twiss (HBT) interferometry is a powerful tool to study the space-time extent of a particle emitting source in heavy ion collisions. PHENIX has measured the azimuthal angle dependence of HBT radii with respect to the 2\textsuperscript{nd} and 3\textsuperscript{rd}-order event planes in Au$+$Au collisions at $\sqrt{s_{NN}}= 200$~GeV. The results for the 2\textsuperscript{nd}-order dependence indicate that the initial eccentricity is reduced during the medium evolution, but not reversed in the final state, which is consistent with previous results. In contrast, the results for the 3\textsuperscript{rd}-order dependence indicate that the initial triangular shape is signicantly reduced and potentially reversed by the end of the medium evolution, and that the 3\textsuperscript{rd}-order oscillations are largely dominated by the dynamical effects from triangular flow. The measurement of the HBT radii from different particle correlations such as charged kaons over the wide $m_T$ ranges give deeper insight on the emission source dynamics. We will report and discuss these new comprehensive HBT measurement in Au$+$Au collisions at $\sqrt{s_{NN}} = 200$~GeV.

Speaker: Shinichi Esumi (University of Tsukuba (JP))

Slides qm14hbt-phenix-esumi.pdf

12:30 HBT and collective flow at mid-rapidity in $d$$+$Au collisions

Recent results obtained at RHIC and the LHC have revealed the presence of unexpected collective effects in central $p(d)$$+$A collisions. Different techniques and physical observables have been utilized to understand whether these collective effects have a similar origin to heavy ion collisions or can be explained solely by cold nuclear matter effects. Two-pion Bose-Einstein correlation is a valuable tool for studying the space-time extent of emission sources in $p(d)$$+$A and A$+$A interactions, while the measurement of the charged particle momentum anisotropy helps in understanding of the collision collective dynamics. In this talk we report new PHENIX results for these observables. PHENIX has extracted the 3D HBT radii as a function of centrality and transverse-pair momentum ($k_T$), for the $d$$+$Au and Au$+$Au collision systems. A comparison of the radii for both systems indicate strong similarities in the detailed dependencies on centrality and $k_T$, suggestive of important final-state rescattering effects in the reaction dynamics for the $d$$+$Au and Au$+$Au systems. The measurements also point to a smaller freeze-out size and system lifetime in $d$$+$Au as compared to Au$+$Au. We also report recent PHENIX results for elliptic flow measured for charged hadrons near midrapidity in $d$$+$Au collisions that complement recent analyses by experiments at the LHC. We observe qualitatively similar, but larger, anisotropies in $d$$+$Au collisions compared to those seen in $p$$+$Pb collisions at the LHC that is consistent with expectations from hydrodynamic calculations owing to the larger expected initial-state eccentricity. The combined HBT and flow data provide significant constraints on hydrodynamic and glasma diagram explanations.

Speaker: Nuggehalli AJITANAND (Stony Brook University)

Slides Ajit_QM14D2.pdf Ajit_QM14D2.pptx

12:50 QGP properties from flow and correlations

Recently the results of azimuthal HBT measurements with respect to the second and third order event plane are presented by PHENIX [1]. They extract $\epsilon_2$ and $\epsilon_3$ from the HBT radii which contain information about not only the source shape at freezeout but also the space-time evolution of QGP matter. They show the relation between initial $\epsilon_{2, 3}$ which are obtained using a Glauber model and final $\epsilon_{2,3}$ which are extracted from the HBT radii. They find that the final $\epsilon_2$ from the HBT radii is finite and smaller than the initial $\epsilon_2$. On the other hand, the final $\epsilon_3$ is vanishing, in spite of existence of finite initial $\epsilon_3$. The interesting different response of $\epsilon_2$ and $\epsilon_3$ during space-time evolution gives us a clue to understand the detailed QGP properties. For analyses of such high statistics experimental results, we develop a state of the art numerical scheme of causal viscous hydrodynamics for relativistic heavy ion collisions, which has a shock-wave capturing scheme and less numerical dissipation [2]. Furthermore, using the hydrodynamic algorithm, we construct a hybrid model of hydrodynamic model plus UrQMD to include the realistic freezeout processes. Using the model we investigate the time evolution of spatial anisotropies $\epsilon_n$. We find that the sign of $\epsilon_3$ changes from positive to negative during the space-time evolution, which suggests a solution of the vanishing final $\epsilon_3$ from the HBT radii by PHENIX. From detailed analyses from flow and correlations, we discuss the initial conditions of hydrodynamic model and the detailed QGP properties such as transport coefficients. [1] T. Niida for the PHENIX collaboration, Nucl. Phys. A 904-905C (2013) pp. 439-442 [arXiv:1304.2876] [2] Y. Akamatsu, S. Inutsuka, C. Nonaka, M. Takamoto, J. Comp. Phys. (2014), pp. 34-54, [arXiv:1302.1665]

Speaker: Chiho Nonaka (Nagoya University)

Slides qm2014_nonaka.pdf

13:10 Azimuthally differential pion femtoscopy in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with ALICE at the LHC

Femtoscopy of non-central heavy-ion collisions provides access to information on the geometry of the effective pion-emitting source. In particular, its shape can be studied by measuring femtoscopic radii as a function of the emission angle relative to the collision plane of symmetry. We present the first measurements of azimuthally differential femtoscopy in Pb-Pb collisions $\sqrt{s_{\rm NN}}$ = 2.76 TeV at the LHC and compare our results to RHIC experiments at lower energies. We measure oscillations of the extracted radii versus the emission angle. We find that $R_{\rm side}$ and $R_{\rm out}$ oscillate out of phase. We show that the relative amplitude of the $R_{\rm side}$ oscillation decreases in more central collisions, but always remains positive. This indicates that the source is out-of-plane extended, which is qualitatively similar to that observations at RHIC energies. We compare our results to existing hydrodynamical and transport model calculations.

Speaker: Vera Loggins (Wayne State University (US))

Slides QuarkMatter2014_Darmstadt_LOGGINS.pdf

11:10 → 13:30 QCD phase diagram: 3

Convener: Alexander Sorin (Joint Inst. for Nuclear Research (RU))

announcement QM2014_announcement_Wed.pdf

11:10 Energy dependence of higher moments of net-kaon, net-proton and net-charge multiplicity distribution at STAR

The main goal of the Beam Energy Scan (BES) program at RHIC is to map the phase diagram of QCD. A critical point (CP) is expected at large baryonic chemical potential ($\mu_{B}$) in the $T$ vs. $\mu_{B}$ phase diagram. Its location experimentally will provide one of the most stringent tests of QCD calculations. In the BES program $T$ and $\mu_{B}$ are varied by changing the center of mass energy ($\sqrt{s_{NN}}$) from 200 to 7.7 GeV. The observables chosen for CP search are the product of moments of conserved(like net-charge) multiplicity distributions or their proxies (such as net-kaon for net-strangeness and net-proton for net-baryons) measured in the experiments. The various moments (mean ($M$), standard deviation ($\sigma$), skewness ($S$) and kurtosis ($\kappa$)) are related to correlation length ($\xi$) of the system (variance: $\sigma^{2}$ $\sim$ $\xi^{2}$; skewness: $S$ $\sim$ $\xi^{4.5}$ and kurtosis: $\kappa$ $\sim$ $\xi^{7}$) [1] and are expected to show a non-monotonic variation with beam energy in the presence of CP. We report new measurements of product of moments: $\sigma^{2}/M$, $S\sigma$ and $\kappa\sigma^{2}$ of net-kaon distributions ($\Delta N_{K}$ = $N_K^+$ - $N_K^-$) obtained by the STAR detector at midrapidity for various centrality in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV. These results will be presented along with the corresponding results from net-charge [2] and net-proton distributions[3]. All the results are corrected for particle reconstruction efficiency and will be compared to baseline distributions constructed following Poisson and Negative Binomial/Binomial statistics. They will also be compared to calculations from HIJING, AMPT and UrQMD models, which do not include a CP. Deviations from some of the baseline measures and model calculations are observed for net-kaon and net-proton distributions. The implications of the observation to CP physics will be presented. References 1. M. A. Stephanov, Phys. Rev. Lett. 102, 032301 (2009); Phys. Rev. Lett. 107, 052301 (2011); C. Athanasiou, et al., Phys. Rev. D 82, 074008 (2010). 2. L. Adamczyk, et al., (STAR Collaboration), arXiv:1402.1558. 3. L. Adamczyk, et al., (STAR Collaboration), Phys. Rev. Lett. 112,

Speaker: AMAL SARKAR (iit-bombay)

Slides QM2014_Amal.pdf

11:30 Freeze-out conditions from fluctuations of conserved charges: lattice meets experiment

Recent results for moments of multiplicity distributions of net-protons and net-electric charge from the Star collaboration are compared to recent lattice QCD results for higher order fluctuations of baryon number and electric charge by the Wuppertal-Budapest collaboration. All lattice simulations are performed at the physical mass for light and strange quarks; all results are continuum extrapolated. We show that it is possible to extract an upper value for the freeze-out temperature, as well as precise baryo-chemical potential values corresponding to the four highest collision energies of the experimental beam energy scan. Consistency between baryon number and electric charge is also discussed.

Speaker: Claudia Ratti

Slides talk_Darmstadt_ratti.pdf

11:50 Baseline for the energy dependence of higher moments of net-proton multiplicity distributions

Experimental confirmation of the QCD critical point is an excellent test of QCD theory in the non-perturbative region and a milestone of exploring the QCD phase diagram. It is one of the main goals of the RHIC Beam Energy Scan (BES) program. Due to the high sensitivity to the correlation length [1] of the dynamical system and directly connected to the susceptibilities in theoretical calculations, for example, the Lattice Gauge Theory (LGT) calculations [2], higher moments of multiplicity distributions have been applied to search for the QCD critical point in the heavy-ion collision experiment. To extract the CP signal in heavy-ion collisions, it is crucial to understand the non-CP effects, such as the effects of conservations for charges (electric, baryon number and strangeness number) and resonance decays, on the experimental observable. In this talk, we will present the comparison between baseline/model with recently published experimental results [3]. We will discuss the deviations of the data from Poisson, binomial baselines as well as the implications. In addition, the results from HRG, AMPT and UrQMD model will be compared with the experimental results. [1] M. A. Stephanov, Phys. Rev. Lett. 102, 032301 (2009); Phys. Rev. Lett. 107, 052301 (2011); C. Athanasiou, et al., Phys. Rev. D 82, 074008 (2010). [2] S. Gupta, X. Luo, B. Mohanty, H. G. Ritter, N. Xu, Science 332, 1525 (2011); F. Karsch and K. Redlich, Phys. Lett. B 695, 136 (2011); A. Bazavov et al., Phys. Rev. Lett.,109, 192302 2012); S. Borsanyi et al., Phys. Rev. Lett.111, 062005 (2013). [3] STAR Collaboration, Phys. Rev. Lett. 112, 032302 (2014).

Speaker: Dr Xiaofeng Luo (Central China Normal University)

Slides Xiaofeng_qm2014.pdf

12:10 Determination of freeze-out conditions from fluctuation observables measured at RHIC

Fluctuations in the conserved charges of the strong interaction are important probes in high-energy heavy-ion collisions, which provide an excellent opportunity for revealing details in the phase structure of QCD matter. Recently, net-electric charge and net-proton fluctuations measured in the beam energy scan program at RHIC were reported by the STAR collaboration. In this talk, we present a new freeze-out curve, which is determined from a combined fit to these fluctuation observables within a phenomenological approach based on the hadron resonance gas model. We also point out that net-strangeness fluctuations may indicate a separate freeze-out behavior of strange hadrons. For a realistic description, we apply the relevant kinematic cuts and systematically include final state effects such as resonance decays and regenerations. The inclusion of the successive regeneration and decay of resonances turns out to be crucial for reconciling calculations of net-proton fluctuations with those of net-baryon number fluctuations and for obtaining reasonable freeze-out conditions.

Speaker: Dr Marcus Bluhm (North Carolina State University)

Slides QM2014Bluhm.pdf

12:30 From conserved charge fluctuations to the QCD critical point

Higher order cumulants of fluctuations of conserved charges are an important diagnostic tool for the thermodynamic properties of strong interacting matter close to freeze out [1] at LHC energies as well as in the entire energy range covered with the beam energy scan (BES) at RHIC. We present recent progress on the calculation of conserved charge fluctuations with highly improved staggered quarks (HISQ action). In particular we will focus on higher order cumulants up to 6th order of net baryon number, net electric charge and net strangeness fluctuations. We will discuss how these quantities approach the hadron resonance gas at low temperatures, the perturbative limit at high-T [2] and analyze to what extent they show sensitivity to universal scaling behavior, *i.e.* we estimate the relative strength of contributions from the regular and singular part of the free energy. Based on this analysis we discuss consequences for the QCD phase diagram and the radius of convergence of the Taylor expansion of the QCD partition function. The latter can be used to locate the QCD critical point. Furthermore, we comment on the signature of the QCD critical point in various ratios of conserved charge fluctuations that are measured in the BES at RHIC. **References** 1. A. Bazavov, H.-T. Ding, P. Hegde, O. Kaczmarek, F. Karsch, E. Laermann, S. Mukherjee and P. Petreczky, C. Schmidt, D. Smith, W. Soeldner and M. Wagner, *``Freeze-out Conditions in Heavy Ion Collisions from QCD Thermodynamics,''* Phys. Rev. Lett. **109** (2012) 192302 [arXiv:1208.1220 [hep-lat]]. 2. A. Bazavov, H.-T. Ding, P. Hegde, F. Karsch, C. Miao, S. Mukherjee, P. Petreczky and C. Schmidt and A. Velytsky, *``Quark number susceptibilities at high temperatures,''* Phys. Rev. **D88** (2013) 094021 [[arXiv:1309.2317 [hep-lat]].

Speaker: Christian Schmidt (University of Bielefeld)

Slides Schmidt_QM14_v2.pdf

12:50 What are multiplicity distributions telling us on QCD phase diagram?

We report a new way to extract the QCD phase transition from the net baryon multiplicity. The method provides us not only a freeze-out temperature- density point, but also the neighbour of the point. In other words, Beam Energy Scan explores not only points, but also regions with the finite spreads in $\mu$-$T$ plane, where $\mu$ is the chemical potential, and $T$ is the temperature. First, we develop a formula in which canonical partition functions are constructed from multiplicities data for a conserved quantity. From the canonical partition functions, we construct the grand partition functions as a function of the fugacity, $\exp(\mu/T)$, from which we can investigate the system when it goes near to the QCD phase transition line. We discuss the applicability limit that comes from the maximum number of the multiplicity measured in experiments. We extend the fugacity to the complex number region, and show the Lee-Yang zero structure, which allows us to see the statistical nature of the system. We calculate the Lee-Yang zero structure by the lattice QCD simulations, and find a very striking feature, i.e., the Roberge-Weiss transition at the deconfinement regions. We investigate the net-proton multiplicity data at RHIC, although it is not a conserved quantity. Using the proposed method, we calculate the susceptibility and kurtosis as a function of $\mu/T$ for each $T$, and the Lee-Yang zeros, and compare them with those of the lattice QCD results.

Speaker: Atsushi Nakamura (Hiroshima Univ)

Slides ANakamura-v5.pdf

13:10 Multiplicity fluctuation from hydrodynamic noise

We discuss multiplicity fluctuation caused by noises during hydrodynamic evolution of the quark-gluon fluid created in high-energy nuclear collisions. In this talk, we claim the following non-trivial consequences within a framework of relativistic fluctuating hydrodynamics [1]: - Multiplicity (being approximately proportional to entropy) fluctuates from event to event due to hydrodynamic fluctuation of dissipative currents such as shear stress tensor and bulk pressure even if the initial state is the same in a macroscopic sense. - *Event-averaged* entropy has to increase with time so that the system obeys the second law of thermodynamics as it should be. Entropy in a certain event can, however, *decrease* with time temporarily and locally due to the hydrodynamic fluctuations. - The probability of decreasing entropy during hydrodynamic evolution is, of course, very small in general. Interestingly, the probability is quantified by the *fluctuation theorem* [2] as known in the non-equilibrium statistical mechanics. We first discuss the fluctuation theorem in non-equilibrium statistical mechanics [2]. The fluctuation theorem has been a milestone in non-equilibrium statistical mechanics since the linear response theory was established. Since the fluctuation theorem contains the Green-Kubo formula at long-time limit, it is believed to capture some important properties of non-equilibrium processes away from equilibrium. We next solve the stochastic equation for dissipative currents together with the temporal evolution equation for the energy density in one-dimensionally expanding coordinate [3] to demonstrate that the final entropy fluctuates from event to event for a given initial condition. During the time evolution of the total entropy in a certain event, reduction of the entropy occurs due to hydrodynamic fluctuation of dissipative currents. We show that the probability of decreasing entropy just obeys the above-mentioned fluctuation theorem. We finally discuss the physics consequences of hydrodynamic fluctuations on final observables. Fluctuation of the final entropy is taken over by the one of multiplicity. Thus we discuss multiplicity distribution functions from a hydrodynamic fluctuation point of view. We also discuss observables in small system such as p+p or p/d+A collisions since the effect of fluctuations are of particular importance in such smaller systems. **References** [1] K. Murase and T. Hirano, arXiv:1304.3243 [nucl-th]. [2] G. Gallavotti and E. G. Cohen, Phys. Rev. Lett. **74**, 2694 (1995); D. J. Evans and D. J. Searles, Phys. Rev. E **52**, 5839 (1995). [3] J. D. Bjorken, Phys. Rev. D **27**, 140 (1983).

Speaker: Tetsufumi Hirano (Sophia Univ)

Slides hirano_QM2014.pdf

11:10 → 13:30 Jets: 5

Convener: Xin-Nian Wang (Lawrence Berkeley National Lab. (US))

announcement QM2014_announcement_Wed.pdf

11:10 b-jet tagged nuclear modification factors in heavy ion collisions with CMS

The energy loss of jets in heavy-ion collisions is expected to depend on the flavor of the fragmenting parton. Thus, measurements of jet quenching as a function of flavor place powerful constraints on the thermodynamical and transport properties of the hot and dense medium. Measurements of the nuclear modification factors of the heavy-flavor-tagged jets in both PbPb and pPb collisions can quantify such energy loss effects. Specifically, pPb measurements provide crucial insights into the behavior of the cold nuclear matter effect, which is required to fully understand the hot and dense medium effects on jets in PbPb collisions. In this talk, we present the b-jet spectra and the first measurement of the nuclear modification factors as a function of transverse momentum and pseudorapidity, using the high statistics pp, pPb and PbPb data taken in 2011 and 2013.

Speaker: Kurt Eduard Jung (Purdue University (US))

Slides kjung-QM2014_v5.pdf

11:30 Jet (de)coherence in Pb-Pb collisions at the LHC

We study the modifications of jets created in heavy-ion collisions at LHC energies. The inherent hierarchy of scales governing the jet evolution allows to distinguish a leading jet structure, which interacts coherently with the medium as a single color charge, from softer sub-structures that will be sensitive to effects of color decoherence. We argue how this separation comes about and show that this picture is consistent with experimental data on reconstructed jets at the LHC, providing a quantitative description simultaneously of the jet nuclear modification factor, the missing energy in di-jet events and the modification of the fragmentation functions. In particular, we demonstrate that effects due to color decoherence are manifest in the excess of soft particles measured in fragmentation functions in Pb-Pb compared to proton-proton collisions.

Speaker: Dr Konrad Tywoniuk (Universitat de Barcelona)

Slides QM2014_KT.pdf

11:50 Zeroing in on the initial state - tomography combining bulk, jet and electromagnetic observables

One of the unsolved problems in the current 'standard model' of heavy ion physics is the apparent rapid thermalization of QCD matter in the pre-equilibrium stage. While it is challenging to probe this mechanism directly, there are now several observables available which allow tomographic imaging of the initial state geometry, which is expected to carry remnant information of the equilibration mechanism. On the fluid dynamics side, scaled fluctuations in the momentum space anisotropy parameters v_n image the initial eccentricity fluctuations epsilon_n almost directly with only a weak dependence on fluid dynamics. From a different direction, due to the strong non-linear dependence of their emission rates on temperature, thermal photons and their v_n are very sensitive to the initial state graininess. Finally, the v_2 and v_3 of high P_T hadrons coming from hard processes reflect the attenuation pattern of partons propagating through the inhomogeneous matter density after some fluid dynamical evolution. Combining information from all these channels does not yet lead to a fully consistent picture, however intriguing trends pointing towards non-trivial initial state dynamics emerge. I review efforts to constrain the initial state by looking at all three classes of observables.

Speaker: Thorsten Renk (University of Jyväskylä)

Slides trenk-qm14.pdf

12:10 Jet quenching in strongly coupled plasma

We present calculations in which a light quark shoots through a finite slab of strongly coupled $\mathcal{N} = 4 $ supersymmetric Yang-Mills plasma, with thickness $L$, focussing on what comes out on the other side. We find that even when the "jets'" that emerge from the plasma have lost a substantial fraction of their energy they look in almost all respects like "jets" in vacuum with the same reduced energy. The one possible exception is that the opening angle of the "jet" is larger after passage through the slab of plasma than before. Along the way, we obtain a fully geometric characterization of energy loss in the strongly coupled plasma and show that $dE_{\rm out}/dL$ is proportional to $L^2/\sqrt{x_{\rm stop}^2-L^2}$, where $E_{\rm out}$ is the energy of the "jet" that emerges from the slab of plasma and $x_{\rm stop}$ is the (previously known) stopping distance for the light quark in an infinite volume of plasma.

Speaker: Krishna Rajagopal (Massachusetts Inst. of Technology (US))

Slides QM2014_Rajagopal.pdf

12:30 A hybrid strong/weak coupling approach to jet quenching

We propose and explore a new hybrid approach to jet energy loss in a strongly coupled medium. The basis of this phenomenological approach is to treat physics processes at different energy scales differently. The high-$Q^2$ processes associated with the QCD evolution of the jet from the hard production up to hadronization are treated perturbatively, following DGLAP evolution, to which we ascribe a space-time structure. The interactions of the shower partons with the deconfined matter leads to energy loss, which is dominated by soft processes and therefore, strong coupling effects are important. These interactions are modeled as inferred from studying energy loss of energetic probes via the gauge/gravity duality. We embed this hybrid model into a model for the production and expansion of hot QCD matter produced in heavy ion collisions and confront it to high energy jet data at the LHC. We also confront the results of this model to the energy loss mechanism dominant at weak coupling.

Speaker: Daniel Pablos (Universitat de Barcelona)

Slides PablosQM.pdf

12:50 NLO transverse momentum broadening and QCD evolution of qhat

There have been a lot of efforts focused on qualitative and quantitative studies of the properties of the sQGP through jet quenching. However, it is not clear whether the properties of the medium such as the jet transport parameter as probed by a propagating jet is unique and intrinsic to the medium, independent of the hard processes that produce the energetic jets. This is a problem of factorization of multiple scattering in QCD and so far has eluded many theoretical efforts. In this talk, we show you the first complete NLO calculation of transverse momentum broadening in SIDIS e+A and DY p+A collisions. We demonstrate for the first time how QCD factorization holds for multiple parton scattering and the universality of the associated quark-gluon correlation function or properties of nuclear matter contained  therein as probed by a propagating parton,  independent of the hard processes that create the fast partons. Our calculation also identifies the QCD evolution equation for this quark-gluon correlation function, which determines the QCD scale and jet energy dependence  of the jet transport parameter. We further solve the QCD evolution equation of qhat numerically and determine the scale and energy dependence of the jet transport parameter  in cold and hot dense medium.

Speaker: Hongxi Xing (LANL)

Slides Hongxi_Xing_-_QM14.pdf

13:10 Renormalization of the jet-quenching parameter

In the context of the recently derived probabilistic picture of in-medium jet evolution, arXiv:1311.5823 [hep-ph], we study radiative corrections which yield potentially large double logarithms, $\alpha_s ln^2 L$, for large enough medium length $L$ (arXiv:1304.7677 [hep-ph]).  We show in particular that, due to a large separation of time scales, these corrections can be reabsorbed in a renormalization of the jet-quenching parameter, $\hat q$, in both the collision rate and radiative rate, preserving the probabilistic picture.  As a major consequence of this analysis, the new renormalized quenching parameter is enhanced compared to the standard perturbative estimate. This yields in particular an increase of radiative energy loss of a fast parton traversing a QCD medium, which scales as $L^{2+\gamma}$ where the anomalous dimension $\gamma=2\sqrt{N_c \alpha_s/\pi}$, as compared to the standard estimate that yields a scaling in $L^2$.

Speaker: yacine mehtar-tani (IPhT CEA/Saclay)

Slides QM2014-bis.pdf

13:30 → 14:00 Lunch bags

14:00 → 18:00 excursion + football

Thursday 22 May

09:00 → 10:30 Plenary: 1

Convener: Barbara Jacak (Stony Brook University)

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

09:00 STAR Overview

Speaker: Nu Xu (LBNL)

Slides nxu_QM14_22May2014.pdf nxu_QM14_22May2014.pptx

09:30 CMS Overview

Speaker: Raphael Granier De Cassagnac (Ecole Polytechnique (FR))

Slides 2014.05.22.QM.RGdC.pdf 2014.05.22.QM.RGdC.pptx

10:00 ALICE Overview

Speaker: Jan Fiete Grosse-Oetringhaus (CERN)

Slides JFGO_final_public.pdf JFGO_final_public.ppt

10:30 → 11:00 Coffee break

11:00 → 13:00 Plenary: 2

Convener: Paolo Giubellino (Universita e INFN (IT))

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

11:00 PHENIX Overview

Speaker: He Xiaochun (Georgia State University)

Slides PHENIX_QM14_PlenaryTalk.pdf

11:30 ATLAS Overview

Speaker: Brian Cole (Columbia University (US))

Slides qm2014_atlasoverview_v6.pdf

12:00 HADES Overview

Speaker: Tetyana Galatyuk (Goethe University / EMMI)

Slides To_Be_Used_2014_05_22_Galatyuk_QM14.pptx

12:30 Recent results from lattice QCD and the phase diagram of strongly interacting matter

Speaker: Dr Heng-Tong Ding (Brookhaven National Lab)

Slides QM14_HengTong_web.pdf

13:00 → 14:30 Lunch

14:30 → 16:00 Plenary: 3

Convener: Jean-Paul Blaizot (CNRS)

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

14:30 Review of experimental results in p(d)-nucleus collisions at RHIC and the LHC

Speaker: Anne Sickles (Brookhaven)

Slides sickles_052214.pdf

15:00 Initial state in relativistic nuclear collisions and color glass condensate

Speaker: Francois Gelis

Slides FGelis.pdf

15:30 A unified description of the reaction dynamics from pp to pA to AA collisions

Speaker: Klaus WERNER (subatech)

Slides qm14kw.pdf

16:00 → 16:30 Coffee break

16:30 → 18:30 Plenary: 4

Convener: Berndt Mueller (Duke University)

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

16:30 Fluctuations and the QCD phase diagram

Speaker: Masakiyo Kitazawa (Osaka University)

Slides QM14_kitazawa.pdf QM14_kitazawa.pptx

17:00 Hadron yields and the phase diagram of strongly interacting matter

Speaker: Michele Floris (CERN)

Slides mfloris-qm2014-yields.pdf

17:30 Equation of state and phase diagram of strongly interacting matter

Speaker: Jan M. Pawlowski (University of Heidelberg)

Slides QM14_pawlowski.pdf

18:00 New physics opportunities at high baryon density

Speaker: Alexander Schmah (Lawrence Berkeley National Lab)

Slides aschmah_QM2014_Final.ppt

19:00 → 20:00 Public evening lecture

19:00 Quantum Beauty

Speaker: Prof. Wilczek Frank (MIT)

Friday 23 May

09:00 → 10:30 Plenary: 5

Convener: Zhangbu Xu (Brookhaven National Laboratory)

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

09:00 Experimental results and phenomenology of quarkonium production in relativistic nuclear collisions

Speaker: Anton Andronic (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

Slides Andronic_QM14.pdf

09:30 Dynamics of heavy flavor quarks in high energy nuclear collisions

Speaker: Andrea Beraudo (Universidade de Santiago de Compostela (ES))

Slides talk_beraudo_def.pdf

10:00 Recent results on open heavy flavor observables in relativistic nuclear collisions

Speaker: Min Jung Kweon (Inha University (KR))

Slides QM2014_MinJungKweon.pdf

10:30 → 11:00 Coffee break

11:00 → 13:00 Plenary: 6

Convener: Barbara Krystyna Wosiek (Polish Academy of Sciences (PL))

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

11:00 Experimental results on jets in ultra-relativistic nuclear collisions

Speaker: Yen-Jie Lee (Massachusetts Inst. of Technology (US))

Slides 20140523-QM2014_yenjie-v5.pdf

11:30 Theory of jet quenching in ultra-relativistic nuclear collisions

Speaker: Guang-You Qin (Central China Normal University)

Slides qm2014_qin.pdf

12:00 AdS CFT for the early stages of heavy ion collisions

Speaker: Romuald Janik

Slides qm2014_janik.pdf

12:30 Neutron star equation of state through current and future observations

Speaker: Anna Watts

Slides QM2014_final_Watts_windows.ppt

13:00 → 14:30 Lunch

14:30 → 16:00 Plenary: 7

Convener: Maria Paola Lombardo (INFN)

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

14:30 Low and intermediate mass di-lepton production in high energy nuclear collisions

Speaker: Lijuan Ruan

Slides QM2014_Ruan.pdf QM2014_Ruan.pptx

15:00 Phenomenology of photon and di-lepton production in relativistic nuclear collisions

Speaker: Elena Bratkovskaya (FIAS)

Slides Bratkovskaya_QM14.pdf

15:30 Theoretical aspects of photon production in high energy nuclear collisions

Speaker: Jacopo Ghiglieri (Technische Universitaet Muenchen)

Slides ghiglieri_qm2014.pdf

16:00 → 16:30 Coffee break

16:30 → 18:30 Plenary: 8

Convener: Carsten Greiner (University of Frankfurt)

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

16:30 Correlations and fluctuations in high energy nuclear collisions

Speaker: Dr Jiangyong Jia (State University of New York (US))

Slides jiangyong_jia_qm2014.pdf

17:00 Collective dynamics in relativistic nuclear collisions

Speaker: Harri Niemi (University of Jyväskylä)

Slides Niemi_QM14.pdf

17:30 Theoretical developments in thermal field theory

Speaker: Chihiro Sasaki

Slides qm.pdf

18:00 New theoretical developments for the physics of strongly coupled systems

Speaker: Uwe-Jens Wiese (Universität Bern)

Slides Darmstadt2014.pdf

18:45 → 18:50 Bus departure to conference dinner site

19:30 → 23:00 Conference dinner

Saturday 24 May

09:00 → 10:30 Plenary: 9

Convener: Bikash Sinha (Variable Energy Cyclotron Centre, Kolkata, India)

slides ICPAQGP2015_Presentation_QM.pdf QM2014_announcement_proceedings.pdf

09:00 Baryonic matter and beyond

Speaker: Kenji Fukushima (Keio University)

Slides fukushima.pdf

09:30 Joint EPJ A and EPJ C lecture: The physics program of FAIR

Speaker: Subhasis Chattopadhyay (Department of Atomic Energy (IN))

Slides subhasis-qm2014-final.pptx

10:00 Physics prospects at RHIC and plans for an eA collider

Speaker: Thomas Ullrich (Yale University (US))

Slides RHIC_eRHIC_Future_Ullrich.pdf

10:30 → 11:00 Coffee break

11:00 → 12:40 Closing session

Convener: Hideki Hamagaki (University of Tokyo (JP))

11:00 Two-gluon correlations in heavy-light ion collisions

Speaker: Douglas Wertepny (The Ohio State University)

Slides wertepny_QM2014_flashtalk.pdf

11:05 Inclusive jet spectra in p-Pb collisions at ALICE

Speaker: Megan Elizabeth Connors (Yale University (US))

Slides flashtalk_connors_QM14.pptx

11:10 Centrality dependence of the J/ψ production in p-Pb collisions with ALICE at the LHC

Speaker: Igor Lakomov (Universite de Paris-Sud 11 (FR))

Slides Lakomov_Flash_QM14.pdf

11:15 Performance and study of B meson spectra in pp and pPb collisions in CMS

Speaker: Gian Michele Innocenti (Massachusetts Inst. of Technology (US))

Slides FlashTalk_Final_Innocenti.pdf

11:20 Systematic studies of the centrality dependence of soft photon production in Au+Au collisions with PHENIX

Speaker: Benjamin Bannier

Slides slides.pdf

11:25 Triangular flow of inclusive charged and identified particles at RHIC

Speaker: Xu Sun (Lawrence Berkeley National Laboratory)

Slides Identified_Particle_v3.pptx

11:30 The thermodynamics of heavy-light hadrons at freeze-out

Speaker: Sayantan Sharma (Uni Bielefeld)

Slides ssharma_qm14.pdf

11:35 Relaxation-time approximation and relativistic viscous hydrodynamics from kinetic theory

Speaker: Amaresh Jaiswal (Tata Institute of Fundamental research, Mumbai)

Slides QM2014_Amaresh.pdf

11:40 Elsevier Young Scientist Awards

11:50 2014 Zimanyi Nuclear Theory Medal

Slides ZimanyiMedal-QM14.pdf

12:00 Quark Matter 2015

Speakers: Hideki Hamagaki, Tetsuo Hatsuda

Slides QM2015_presentation_v2.pdf QM2015_presentation_v2.pptx