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 EB: Mini-symposium on Relativistic Heavy Ions, Recombination |
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Sponsoring Units: DNP JPS Chair: Tim Hallman, Brookhaven National Laboratory Room: Ritz-Carlton Hotel Salon 3 |
Wednesday, September 21, 2005 9:00AM - 9:30AM |
EB.00001: Quark Recombination at RHIC Invited Speaker: Recently the recombination of thermalized valence quarks has proposed as the dominant mechanism for the production of hadrons at intermediate transverse momentum (2-4 GeV/c) in relativistic heavy ion collisions. A lot of evidence that suggests the quark recombination has been found in the RHIC data, such as hadron spectra, ratios of hadron yield, nuclear modification factors and elliptic flow as a function of transverse momentum. Especially the quark number scaling in elliptic flow strongly shows the validity of dominance of the recombination mechanism in hadronization. Furthermore the more detailed argument about physical observables at RHIC (correlated emission of hadrons, event-by-event fluctuations, hadronization time, entropy problem) has been done from the point of view of the quark recombination. I will discuss the recent progress of the quark recombination at RHIC. [Preview Abstract] |
Wednesday, September 21, 2005 9:30AM - 9:45AM |
EB.00002: Fluctuations and Correlations in Parton Recombination Steffen Bass, Chiho Nonaka, Rainer Fries, Masayuki Asakawa, Berndt Mueller Parton recombination models have been very successful in explaining data taken at RHIC on hadron spectra, nuclear modification factors and elliptic flow emission patterns in Au+Au collisions at transverse momenta above 2 GeV/c, which have exhibited features which could not be understood in the framework of basic perturbative QCD. Recently, however, more sophisticated dynamical correlation observables, such as jet-like two particle correlations have become available. I will show how these observables can be addressed by the recombination approach through incorporating two-particle correlations into the quark distributions which are used as initial condition for the calculation. In addition, I will discuss entropy-conservation and charge fluctuations in the recombination approach. Finally, I will investigate the possible effect realistic light-cone wave-functions including higher Fock-states may have on the well-known elliptic flow valence-quark number scaling law. [Preview Abstract] |
Wednesday, September 21, 2005 9:45AM - 10:00AM |
EB.00003: Results of Identified pions, kaons, (anti-)protons in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV from STAR Haidong Liu Ultra-relativistic Au+Au collisions at RHIC create a hot and dense medium that exhibits novel properties. Study of these properties and hadronization mechanisms of the medium requires identified particle results over wide transverse momentum ($p_T$) range. In this talk, we will present the results of pions, kaons and (anti-)protons $p_T$ spectra in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV using the STAR detector at RHIC. The particle identification is achieved by a combination of the Time-Of-Flight (TOF) and the Time Projection Chamber (TPC) detectors. The $p_T$ range is measured up to 12 GeV/c for pions, 3 GeV/c for kaons and 6 GeV for (anti-)protons. The particle ratios and the nuclear modification factors ($R_{AA}$ and $R_{CP}$) will be presented. The physics indications of these measurements will be discussed. [Preview Abstract] |
Wednesday, September 21, 2005 10:00AM - 10:15AM |
EB.00004: Baryon/meson Effects in Hot and Cold Nuclear Matter Julia Velkovska A number of exciting phenomena have been observed at intermediate$-p_{T}$ (2 - 5 GeV/c) in heavy ion collisions at RHIC: enhanced proton/pion ratios, particle species dependent yield suppression factors, and quark-number scaling of elliptic flow. Quark-recombination models have been invoked to explain the data, but alternate mechanisms such as baryon junctions and strong radial flow have also been proposed. Particle species dependencies are also seen in the Cronin enhancement measured at RHIC and at lower energies. Measurements involving heavy mesons are necessary to distinguish mass effects from baryon/meson effects. We study the nuclear modification factors for $\phi$-mesons in d+Au and Au+Au collisions at $\sqrt{s_{NN}} = 200 $ GeV as a function centrality and compare to the results for protons and pions. The high-statistics Au+Au data sample obtained in Run-4 of RHIC allows for a v2 measurement of $\phi$ that can be used to further test the empirical quark-scaling rule. We also investigate the effect of baryon transport using $\pi$/K/p spectra from 62 GeV Au+Au collisions. [Preview Abstract] |
Wednesday, September 21, 2005 10:15AM - 10:30AM |
EB.00005: Open Heavy Flavor and J/Psi Production at Large Rapidities in dAu Collisions at RHIC Ming Xiong Liu We study heavy flavor production through prompt muon measurements in the forward and backward rapidities 1.2$<\vert \eta \vert <$ 2.4 in dAu collisions with the PHENIX muon detectors. The rapidity dependence of prompt muon yields is studied as a function of the transverse momentum of the muon. Open charm is predominantly produced through gluon-gluon interactions at RHIC energy, thus such measurements will shed new light on gluon (anti)shadowing in small (large) Bjorken ``x'' in the Au nucleus. We also compare open charm to J/Psi yields in the forward and backward rapidities in dAu collisions and study the origin of the large forward and backward asymmetry observed by the PHENIX experiment in J/Psi production in the dAu collisions. This will help us to understand various normal nuclear effects - such as parton shadowing, initial state energy loss and nuclear absorption - on open charm and J/Psi production at RHIC. The current status of this analysis will be presented [Preview Abstract] |
Wednesday, September 21, 2005 10:30AM - 10:45AM |
EB.00006: Heavy flavor production from single muons in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV Anuj Purwar Heavy flavor production in the dense partonic matter created at RHIC can be modified either by energy loss for heavy quarks or by charm enhancement. Measurement of open charm as a function of centrality will also be critical to interpreting the measured production of J/$\psi$ in Au+Au collisions, as J/$\psi$ production is predicted to be modified by both initial state and final state effects in Au+Au collisions. One way of measuring open charm is to look at single muons from semi-leptonic decays. The PHENIX experiment at RHIC is uniquely positioned to make this measurement using its two muon arms. Single muons from Au+Au collisions have to be extracted from a background of hadron punch throughs and muon decays from light mesons. We present the latest results of open charm from Au+Au collisions using the PHENIX muon arms (pseudorapidity range: $1.2 < |\eta| < 2.4$). [Preview Abstract] |
Wednesday, September 21, 2005 10:45AM - 11:00AM |
EB.00007: Measurements of J/$\Psi$ $\rightarrow$ e$^+$e$^-$ in Au-Aucollisions at $\sqrt{s_{NN}}$ =200 GeV by PHENIX at RHIC Taku Gunji Measurements of the J/$\Psi$ yield in heavy ion collisions are expected to be one of the most promising probes of deconfined matter, since theoretical models predict that the J/$\Psi$ yield could be strongly suppressed due to the color Debye screening effect in Quark Gluon Plasma. Recently, many theoretical efforts have been made to investigate the behavior of J/$\Psi$ production at RHIC energy. One of the interesting predictions that has emerged, is that the $J/\Psi$ yield could be enhanced due to the recombination of uncorrelated $c\bar{c}$ pairs. The PHENIX experiment measured the $J/\Psi$ yield in Au-Au collisions at $\sqrt{s_{NN}} = 200$ GeV by using $e^+e^-$ decay mode at mid-rapidity ($|\eta|<0.35$) and $\mu^{+}\mu^{-}$ decay mode at forward-rapidities ($1.2<|\eta|<2.2$). The latest results of $J/\Psi$ invariant yield and $J/\Psi$ pT distribution obtained by using its $e^+e^-$ decay mode from $\sqrt{S_{NN}}$ = 200GeV Au+Au collisions will be shown. [Preview Abstract] |
Wednesday, September 21, 2005 11:00AM - 11:15AM |
EB.00008: $J/\Psi$ production at forward rapidity in $\sqrt{s_{NN}}$=200 GeV Au-Au collisions in PHENIX experiment MinJung Kweon The modification of heavy quarkonium yields and spectra is considered one of the most promising signatures of the predicted nuclear phase transition into the deconfined quark- gluon plasma. During RHIC run 4, the PHENIX muon spectrometers, covering $1.2 < \eta < 2.4$ and $-1.2 < \eta < -2.2$, yielded several thousands of $J/\Psi$ particles in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. The $R_{AA}$ dependence over centrality, $p_T$ and rapidity will be presented using the $J/ \psi$ production via $\mu^{+}\mu^{-}$ channel. [Preview Abstract] |
Wednesday, September 21, 2005 11:15AM - 11:30AM |
EB.00009: Measurement of $J/\psi$ Polarization via Dielectron Decay Channel in $\sqrt{s_{NN}}=200$ GeV d+Au and Au+Au Collisions by the PHENIX Experiment Alexandre Lebedev Charmonium, and, in particular, $J/\psi$, is considered as a leading probe of the hot and dense matter created in relativistic heavy ion collisions. A good understanding of the $J/\psi$ production mechanism is necessary for studying the properties of this hot and dense matter. One important diagnostic tool for studying $J/\psi$ production mechanisms is the measurement of $J/\psi$ polarization. Such measurement helps to differentiate among various production models, and understand production and subsequent hadronization of charm quark pairs. We present the results of the $J/\psi$ polarization measurement in d+Au and Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by the PHENIX experiment at RHIC. $J/\psi$ polarization is measured as a function of transverse momentum. [Preview Abstract] |
Wednesday, September 21, 2005 11:30AM - 11:45AM |
EB.00010: Production of $\Lambda$ and $\bar{\Lambda}$ particles in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV Debsankar Mukhopadhyay The measurements of $\Lambda$ and $\bar{\Lambda}$ particles are crucial to study the net baryon density and strangeness production in relativistic heavy ion collisions. The PHENIX experiment at RHIC has recorded 1.5 $\times$ $10^{9}$ Au+Au events during 2003-4 run period at RHIC. The data sample will allow us to make a detailed study of the centrality dependence of $\Lambda$ and $\bar{\Lambda}$ yields. We shall present the analysis status of the $\Lambda$ and $\bar{\Lambda}$'s. [Preview Abstract] |
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