Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session DD: Mini-symposium on Strongly Interacting Quark Matter |
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Sponsoring Units: DNP JPS Chair: Yasuo Miake, University of Tsukuba Room: Ritz-Carlton Hotel Salon 1 |
Tuesday, September 20, 2005 7:00PM - 7:30PM |
DD.00001: Event anisotropy in high-energy heavy-ion collisions at RHIC Invited Speaker: The high pT suppression and the baryon/meson scaling of the nuclear modification factor as well as the quark number scaling of the measured elliptic flow parameter at intermediate pT region are the most exciting findings in high-energy heavy-ion collisions at RHIC. This observation is one of the strongest evidences to support the formation of quark gluon plasma (QGP). The detailed study on event anisotropy and analysis of azimuthal particle correlation especially as a function of pT, centrality, particle species, collision system size and beam energy would enable us to understand the mechanism of the observed scaling behavior. The results of such systematic study will be shown and the possible origin of the elliptic flow will be investigated and discussed. [Preview Abstract] |
Tuesday, September 20, 2005 7:30PM - 7:45PM |
DD.00002: Rapidity Dependence of Pion Elliptic Flow at RHIC S.J. Sanders, E. Johnson, H. Ito The measured elliptic flow (v$_{2}$) of identified particles as a function of p$_{t}$ and centrality at RHIC suggests the created medium in Au+Au collisions achieves early local thermal equilibrium that is followed by hydrodynamic expansion. These measurements of identified particle v$_{2}$ have been limited, however, to a narrow region about mid-rapidity. Charged-hadron v$_{2}$ measurements show a significant reduction at forward pseudorapidities. It is not known if this $\eta$ dependence is a general feature of elliptic flow, or reflects other changes in the particle spectra in going to the forward region. The BRAHMS experiment provides unique capabilities to measure v$_{2}$ at forward rapidities. Using the BRAHMS multiplicity array to determine the v$_{2}$ event plane, identified particle elliptic flow can be measured using the BRAHMS spectrometers, with $0\le \eta \le 3.4$. This talk will discuss pion elliptic flow at $\eta$ = 0, 1, 2.7 and 3.4 from Run 4 Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. In addition, the p$_t$ integrated flow for charged hadrons obtained using just the multiplicity array will be presented. This work was supported by the Office of Nuclear Physics of the U.S. Department of Energy. [Preview Abstract] |
Tuesday, September 20, 2005 7:45PM - 8:00PM |
DD.00003: The azimuthal anisotropy of electrons from heavy flavor decays in $\sqrt{s_{NN}}$ = 200 GeV Au-Au collisions by PHENIX Shingo Sakai The azimuthal anisotropy of particle emissions is a powerful tool to study the early stage of ultra-relativistic nuclear collisions. Previous measurements of $v_{2}$ for hadrons made of light quarks, such as pions and kaons, are consistent with the quark coalescence model, which assumes that hadrons derive their $v_{2}$ from the quarks that form them. This suggests that the $v_{2}$ already develops in the partonic phase for hadrons made of light quarks. In addition if the $v_{2}$ of heavy flavor is non-zero, it would suggest partonic level thermalization and very high density at the early stage of the collisions. In this presentation, we will show the azimuthal anisotropy of heavy flavor by measuring the electron $v_{2}$ from semi- leptonic charm decays in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV in RHIC-RUN4 and compare with several theoretical predictions. [Preview Abstract] |
Tuesday, September 20, 2005 8:00PM - 8:15PM |
DD.00004: Measurement of single electron azimuthal angular anisotropy v2 from Au+Au collisions at $\sqrt{s_{NN}}$ 200 GeV Weijiang Dong We present results of v2 measurement for single electrons/positrons covering a pT range from 1.5 to 6 GeV/c. These electrons are mostly from semi-leptonic decays of heavy quark mesons whose pT range covers approximately from 3 to 12 GeV/c. The elliptic flow parameter v2 in this pT range addresses two important physics issues: the hadronization of bulk partonic matter and the energy loss of heavy quarks in the dense medium created in nucleus-nucleus collisions at RHIC. A Constituent Quark Number(CQN) scaling in v2 has been observed in hadrons of light quarks, which has been interpreted as features of hadronization of bulk partonic matter through quark coalescence or recombination. If the heavy quark v2 follows the same CQN scaling as light quarks, it implies that these heavy quarks may have become a part of the bulk partonic matter through dynamic evolution in the medium and its hadronization mechanism is similar to that of light quarks. At pT above the recombination region, the energy loss is one possible dynamics to create azimuthal angular anisotropy. The measurement of v2 for heavy quark mesons will complement the measurement of nuclear modification factor in determining the heavy quark energy loss. [Preview Abstract] |
Tuesday, September 20, 2005 8:15PM - 8:30PM |
DD.00005: Measurement of Non-photonic Electron Anisotropic Flow in $\surd $s$_{NN}$=200 GeV Au+Au Collisions Andrew Rose In order to understand the partonic EOS of matter created at RHIC, one needs to study both the collectivity of the produced matter and the degree of thermalization. Anisotropic flow measurements have already demonstrated the development of partonic collectivity at RHIC [1]. The next step is to address the issue of thermalization. Since the masses of the heavy flavor quarks are much larger than the possible excitation of the system created in the collision, their collective motion could be used to indicate the thermalization of light flavors (u-,d-, s- quark hadrons). It has been shown that the information of charm hadron flow can be extracted from their semi-leptonic decay in the region pT $>$ 2GeV/c [2]. In this talk, we report the STAR preliminary results of non-photonic electron v2 from 200GeV Au+Au collisions. The data is from the high statistics run IV at RHIC. Both STAR TPC and the TOF tray were used in the analysis to identify electrons. A systematic comparison of the electron v2 with both hadronic v2 results and theory predictions will be discussed. [1] Phys. Rev. Lett. 86 (2001) 402 [2] X. Dong et al., Phys. Lett. B(2004); Ko et al., PRC (2004) [Preview Abstract] |
Tuesday, September 20, 2005 8:30PM - 8:45PM |
DD.00006: Heavy Quarkonia in Quark-Gluon Plasma Cheuk-Yin Wong Does the $Q$-$\bar Q$ potential from lattice gauge data yield a $J/\psi$ dissociation temperature $\sim $1.6 $T_c$ as in lattice spectral function analyses? Is there a strong coupling between a static $Q$ and $\bar Q$ in their color-singlet states in the quark-gluon plasma? From a variational principle, we find the color-singlet $Q$-$\bar Q$ potential to be $f_F F_1+(1-f_F) U_1$, where $F_1$ is the lattice gauge color-singlet free energy, $U_1$ the internal energy, $f_F=3/(3+a(T))$, and $a(T)=$3(pressure)/(energy density) is from the equation of state. We find that $J/\psi$ dissociates spontaneously above 1.56 $T_c$, while $\chi_c$ and $\psi'$ are unbound in the quark-gluon plasma. Our analysis lends support to the theoretical result that $J/\psi$ is bound up to $\sim$1.6 $T_c$. However, $J/\psi$ has a binding energy $\sim$ 0.04 GeV at 1.13 $T_c$, indicating that the coupling between a static $Q$ and $\bar Q$ in their color-singlet states is quite weak in the quark-gluon plasma. For details, please browse http://www.arxiv.org/pdf/hep-ph/0408020. [Preview Abstract] |
Tuesday, September 20, 2005 8:45PM - 9:00PM |
DD.00007: Study of $J/\Psi$ at high temperatures in anisotropic lattice QCD Hideaki Iida, Noriyoshi Ishii, Hideo Suganuma The high-temperature $J/\Psi$ mode above the QCD critical temperature $T_c$ is studied using anisotropic quenched lattice QCD. We aim to clarify whether the $J/\Psi$ state above $T_c$ is a localized resonance state or a $c$-$\bar c$ scattering state. We investigate $c$-$\bar c$ modes for $1.1T_c< T <2.1T_c$ using the $O(a)$-improved Wilson quark action at $\beta=6.10$ with renormalized anisotropy $a_s/a_t=4$. To distinguish localized states and scattering states, we calculate the $c$-$\bar c$ correlators on finite lattices with different spatial boundary conditions, i.e., the periodic and the anti-periodic boundary condition. (Note that the $c$-$\bar c$ threshold is raised up in the anti-periodic boundary condition.) As a result, almost no energy difference is found for the lowest $J/\Psi$ mode between the periodic and the anti-periodic boundary conditions at for $1.1T_c< T <2.1T_c$. This fact indicates that the lowest $J/\Psi$ mode can survive as a localized state even above $T_c$ in quenched QCD. [Preview Abstract] |
Tuesday, September 20, 2005 9:00PM - 9:15PM |
DD.00008: Multiplicity Fluctuations in Au+Au Collisions from PHOBOS Zhengwei Chai We will present the first PHOBOS results on inclusive charged particle multiplicity fluctuations in Au+Au collisions at 200GeV in the pseudo-rapidity range -3.0 to +3.0. Most dynamical models predict characteristic particle correlations, which can be long range and/or short range, leading to non-statistical dynamic fluctuations. The dynamic fluctuations results as a function of mean pseudo-rapidity and the bin size, are compared to model calculations. The measured dynamic fluctuations are expected to provide useful insights into both short-range and long-range effects in the heavy ion collisions. [Preview Abstract] |
Tuesday, September 20, 2005 9:15PM - 9:30PM |
DD.00009: How to Measure Specific Heat Using Event-by-Event Average $p_T$ Fluctuations. Michael Tannenbaum A simple way to visualize event-by-event average $p_T$ fluctuations is by assuming that each collision has a different temperature parameter (inverse $p_T$ slope) and that the ensemble of events has a temperature distribution about the mean, $\langle T\rangle$, with standard deviation $\sigma_T$ [R.~Korus, {\it et al.} PRC {\bf 64}, 054908\ (2001)]. PHENIX characterizes the non-random fluctuation of $M_{p_T}$, the event-by-event average $p_T$, by $F_{p_T}$, the fractional difference of the standard deviation of the data from that of a random sample obtained with mixed events. This can be related to the temperature fluctuation: \vspace*{-0.13in} \[ F_{p_T}=\sigma^{\rm data}_{M_{p_T}}/\sigma^{\rm random}_{M_{p_T}}-1\simeq(\langle n \rangle -1) \sigma^2_{T}/\langle T\rangle^2 \qquad .\] Combining this with the Gavai, {\it et al.}, [hep-lat/0412036] definition of the specific heat per particle, a simple relationship is obtained: \vspace*{-0.06in} \[ c_v/T^3={{\langle n\rangle}\over {\langle N_{tot}\rangle}} {1\over F_{p_T}} \qquad . \] $F_{p_T}$ is measured with a fraction $\langle n\rangle /\langle N_{tot}\rangle$ of the total particles produced, a purely geometrical factor representing the fractional acceptance, $\sim 1/20$ in PHENIX. The Gavai, {\it et al.} prediction that $c_v/T^3=15$ corresponds to $F_{p_T}\sim 0.33$\%, which may be accessible in PHENIX by measurements of $M_{p_T}$ in the range $0.2\leq p_T\leq 0.6$ GeV/c. [Preview Abstract] |
Tuesday, September 20, 2005 9:30PM - 9:45PM |
DD.00010: Present and future measurements on hadronization in strongly interacting partonic matter at RHIC and RHIC-II. Helen Caines The recent RHIC results establish the necessity for a detailed investigation of the matter formed in heavy-ion collisions at 200 A GeV. In particular, di-jet and gamma-jet measurements with particle identification (PID) out to large momenta are required in order to study experimentally the hadronization process from partonic degrees of freedom and to continue the search for possible evidence of the restoration of chiral symmetry. We will show recent particle identified single particle and two particle correlation measurements at intermediate transverse momentum in pp, da, and AA collisions from the RHIC experiments and compare to fragmentation and recombination models. We then propose a set of hadronic measurements for a future large acceptance (-3 $< $\eta <$ 3, $\Delta\phi= 2\pi$) experiment at RHIC-II with hadron, muon and gamma PID capabilities out to 20-30 GeV/c, tracking detectors, and EM and hadronic calorimetry in a large solenoidal magnetic field (1.5 T). [Preview Abstract] |
Tuesday, September 20, 2005 9:45PM - 10:00PM |
DD.00011: Direct Photons at RHIC-II Gabor David Starting with a quick survey of the latest direct photon results from RHIC we will attempt to make realistic predictions how the detector and luminosity upgrades of RHIC-II can improve upon our understanding of photon production at all momenta. We will argue that in order to fully understand and disentangle the various mechanisms, constrain free parameters in theories and - very important! - to actually map out the transition from nuclear matter to sQGP the RHIC-II upgrades will be essential in part by making rare probes more accessible but also by opening up the possibility of an expedited species/energy scan. [Preview Abstract] |
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