Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session DC: Mini-Symposium on Thermal and Collective Properties of the Quark Gluon Plasma II |
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Chair: Peter Jacobs, Lawrence Berkeley National Laboratory Room: Kohala 1 |
Thursday, October 15, 2009 7:00PM - 7:30PM |
DC.00001: Understanding Thermal and Collective Properties of the Quark Gluon Plasma Invited Speaker: |
Thursday, October 15, 2009 7:30PM - 7:45PM |
DC.00002: Recent results on identified particle spectra from $d+Au$ collisions at RHIC Chitrasen Jena The Cronin effect [1], the enhancement of hadron spectra at intermediate $p_{T}$ in p + A collisions as compared to those in p + p collisions, has received renewed interest at RHIC [2]. It is thought that this effect may reflect on the early parton scatterings in high-energy nuclear collisions. In order to further investigate the Cronin effect, and shed light on the initial conditions at RHIC, we have analyzed the rapidity dependence of $\phi$ meson production in d + Au collisions at RHIC. In this talk, we report on STAR preliminary results of $\phi$ meson transverse momentum distributions(using the hadronic decay mode $\phi$ $\rightarrow$ $K^+K^-$) and charged hadrons spectra from 200 GeV d + Au collisions. The dataset used for this analysis is from STAR's year 8 d + Au collisions with significantly reduced material ($\sim$1/10) and high statistics ($\sim$3) compared with previous runs. The particle species and the mass dependence of the nuclear modification factor as a function of rapidity will be presented. [Preview Abstract] |
Thursday, October 15, 2009 7:45PM - 8:00PM |
DC.00003: Detailed source structures of hadron emissions measured by RHIC-PHENIX Akitomo Enokizono During the first decade of 21th century, experiments at the Relativistic Heavy Ion Collider at BNL have revealed detailed insights into the hot and dense matter created in Au+Au collisions at 200 GeV per nucleon, which is reasonably described as an almost perfect liquid state by hydrodynamics models. Despite our increased understanding of this partonic matter, there still remain some open questions with respect to its space-time evolution. Studies of the space-time evolution of the collisions are needed to elucidate the properties of the hot, dense, and strongly interacting matter, probe the time scale and degree of thermalization, and investigate the order of the deconfinement phase transition. Two-particle interferometry, aka HBT, is a powerful tool for measuring the space-time extent of particle-emitting sources. In addition to the traditional HBT analysis, recent developments of HBT-imaging analyses allow us to measure more detailed model-independent source functions of particle emissions. In this talk, we will show the result of the traditional 3D and 1D imaging analyses for charged kaons in Au+Au at 200 GeV, compared with the previous results for charged pions. Also the latest status of PHENIX-HBT analyses for the other particles/collision systems will be reported. [Preview Abstract] |
Thursday, October 15, 2009 8:00PM - 8:15PM |
DC.00004: Femtoscopy in $\sqrt{s}$ = 200~GeV $p$+$p$ collisions at RHIC-PHENIX Andrew Glenn Femtoscopic measurements from two particle interferometry exploit the {\bf H}anbury {\bf B}rown and {\bf T}wiss effect to provide information about the bulk medium created in heavy-ion collisions. Experiments at the Relativistic Heavy Ion Collider use HBT measurements to study source sizes and emission duration of the strongly interacting {\bf Q}uark {\bf G}luon {\bf P}lasma created in $\sqrt{s}$ = 200~GeV Au+Au collisions. These HBT measurements show azimuthal sensitivity relative to the reaction plane of non-central collisions. Future HBT measurements may similarly use a jet axis to define the event-by-event geometry to gain insight into the modification of jets by the QGP, and conversely, the feedback of the jet into the medium. Understanding HBT in systems with significant correlations due to local energy and momentum conservation, such as $p$+$p$ collisions, will be required to properly perform and interpret such measurements. Comparisons of correlations from minimum bias data to those from a jet region are of particular importance. PHENIX preliminary measurements from the HBT analysis for charged pions from $\sqrt{s}$ = 200~GeV $p$+$p$ collisions will be presented. The status of 1-D imaging and the analysis of jet selected events will be discussed. [Preview Abstract] |
Thursday, October 15, 2009 8:15PM - 8:30PM |
DC.00005: Mach Cones in Heavy Ion Collisions Jorge Noronha We study the fate of the energy deposited by a jet in a heavy ion collision assuming that the medium created is opaque (jets quickly lose energy) and its viscosity is so low that the energy lost by the jet is quickly thermalized. The expectation is that under these conditions the energy deposited gives rise to a Mach cone. We argue that, in general, the behavior of the system is different from the naive expectation and it depends strongly on the assumptions made about the energy and momentum deposited by the jet into the medium. We compare our phenomenological hydrodynamic calculations performed for a variety of energy-momentum sources (including a pQCD-based calculation) with the exact strong coupling limit obtained within the AdS/CFT correspondence. We also discuss the observability of hydrodynamical features triggered by jets in experimentally measured di-hadron correlations at RHIC. [Preview Abstract] |
Thursday, October 15, 2009 8:30PM - 8:45PM |
DC.00006: Attenuation of Dynamical Density Fluctuation around QCD Critical Point and its Phenomenological Implications Yuki Minami, Teiji Kunihiro We explore the dynamical density fluctuations around the QCD critical point (CP) using dissipative relativistic fluid dynamics in which the coupling of the density fluctuations to those of other conserved quantities is taken into account. We show that the sound mode which is directly coupled to the mechanical fluctuations is attenuated and in turn the thermal mode which comes from the entropy fluctuation becomes the genuine soft mode at the QCD CP, which is actually known for the liquid-gas transition point. A speculation is given on the possible fate of Mach cone in the vicinity of the QCD CP as a signal of the existence of the CP on the basis of the above finding. We also apply and extend the mode-mode coupling theory to the relativistic system to study the properties of the dynamical density fluctuation in the close vicinity of the QCD CP. [Preview Abstract] |
Thursday, October 15, 2009 8:45PM - 9:00PM |
DC.00007: Spectral function of a fermion coupled with a massive vector particle at finite temperature--- analysis on gauge dependence in the Stueckelberg formalism Daisuke Satoh, Yoshimasa Hidaka, Teiji Kunihiro Effective chiral models of QCD suggest that hadronic collective excitations may exist even in the quark gluon plasma(QGP) phase. In turn, the coupling with such a collective mode can lead to a drastic change in the quark quasi-particle picture. We analyze the spectral function of a fermion coupled with a massive vector collective mode at finite temperature in the one-loop order in the Stueckelberg formalism, which has a gauge invariance and is renormalizable so that the correct high temperature limit can be obtained. It is known that the pole position of the fermion propagator is generically independent of the gauge fixing condition, although the residue of the pole has a gauge dependence. In perturbation theory, however, even the pole can also artificially depend on the gauge fixing condition owing to the truncation of the higher order terms. In fact, the pole as well as the residue of the fermion propagator show a dependence on the gauge in our numerical calculation. In this presentation, we are going to propose a prescription to obtain the pole in a gauge-independent way, and discuss the possible quasi-particle picture of a fermion coupled with a massive vector mode. [Preview Abstract] |
Thursday, October 15, 2009 9:00PM - 9:15PM |
DC.00008: Heavy-quark free energy at finite temperature in full-QCD lattice simulations Yu Maezawa, Shinya Aoki, Shinji Ejiri, Tetsuo Hatsuda, Noriyoshi Ishii, Kazuyuki Kanaya, Hiroshi Ohno, Takashi Umeda We present recent results of free energies between a heavy quark and antiquark at finite temperature in 2+1 flavors lattice simulations. We perform simulations on 32$^3$ times 16--4 lattices in fixed scale approach with 2+1 flavors of improved Wilson quark action, and extract static quark free energies from Polyakov-line correlations projected to a color-singlet channel in the fixed Coulomb gauge. As interesting results, at short separation, magnitude of the heavy-quark free energies for any temperatures converges to that of a heavy-quark potential calculated from the Wilson-loop at zero temperature. This suggests that the renormalization is common for all temperature in the fixed scale approach. We also show properties of the Debye screening mass at long separation and discuss dynamical quark effect from comparison with previous studies in two-flavors and quenched QCD simulation. [Preview Abstract] |
Thursday, October 15, 2009 9:15PM - 9:30PM |
DC.00009: Pair Creation of Quarks in Electric Flux Tube Aiichi Iwazaki We discuss the pair production of massless fermions under the flux tube of electric field $\vec{E}$ and homogeneous magnetic field $\vec{B}$, using the formula of chiral anomaly. The tube of the electric field is finite in transverse directions but infinitely long in longitudinal direction. In the limit of $B\gg E$, we can analytically obtain the spatial and temporal behaviors of the electric field and transverse magnetic field generated by currents of the produced particles. We find that the life time $t_c$ of the electric field is shorter as the width of the tube is narrower. Applying the result to the glasma in high-energy heavy-ion collisions, we find that $t_c\simeq 7Q_s^{-1}$ with saturation momentum $Q_s$. [Preview Abstract] |
Thursday, October 15, 2009 9:30PM - 9:45PM |
DC.00010: Direct photon measurement via internal conversions in Cu+Cu collisions at $\sqrt{s_{NN}} = 200\,\mathrm{GeV}$ in PHENIX Daisuke Watanabe The measurement of direct photons on hot and dense matter created in heavy ion collisions can provide thermodynamic information, but their measurement in the low $p_T$ region is very challenging due to large hadronic background. However, internal conversion method allows access to low and intermediate $p_T$ direct photons. In an earlier measurement in Au+Au collisions, direct photon invariant yield was obtained in the pair mass region $M_{ee} < 300MeV/c^{2}$ for transverse momentum $1 < p_{T} < 5GeV/c$. In the case of Au+Au central collisions, direct photon $p_T$ spectra have been fitted to an exponential with inverse slope parameter $T = 221\pm23(stat)\pm18(syst)MeV$, which is higher than critical temperature $T_{c} = 170MeV$ predicted by Lattice QCD~[1]. Therefore, it is interesting to also measure direct photons and the temperature of hot and dense matter created in Cu+Cu collisions, a smaller system that might be expected to reach a lower temperature. The latest status of the measurement is reported. \\[4pt] [1] K.Adcox et al., Nucl.Phys. A757,184 (2005) [Preview Abstract] |
Thursday, October 15, 2009 9:45PM - 10:00PM |
DC.00011: Photon Physics at LHC-ALICE Takuma Horaguchi The ``A Large Ion Collider Experiment'' (ALICE) is to study physics of strongly interacting matter and the quark-gluon plasma (QGP) in heavy ion collisions at Large Hadron Collider (LHC). Production of deconfined partonic phase has been basically proven at the BNL-RHIC, via high pt jet suppression and a constituent quark number scaling in collective motions of hadrons. However, there are topics which should be further investigated, e.g. quantitative understanding thermal properties of the deconfined partonic phase. A unified picture is awaited at the LHC, especially via studies of thermal radiations. At BNL-RHIC, the excess of direct photon yield above binary scalid NLO pQCD in Au+Au collisions is observed with virtual photon measurement via internal conversion. Thermal properties at LHC is expected to be emphasized with the highest energy heavy ion collisions in the world. In this talk, photon physics at LHC-ALICE will be discussed, with an emphasis on thermal radiations with ALICE detector via comparison with various methods of photon measurement in pp and heavy ion collisions. [Preview Abstract] |
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