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 CC: Mini-symposium on Relativistic Heavy Ions, Jet Quenching |
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Sponsoring Units: DNP JPS Chair: Vicki Greene, Vanderbilt University Room: Ritz-Carlton Hotel Salon 2 |
Tuesday, September 20, 2005 2:00PM - 2:30PM |
CC.00001: Parton Energy Loss and Jet Tomography: Probing the ``Perfect Liquid'' at RHIC Invited Speaker: Experimental evidence from RHIC strongly suggests that matter having an energy density far in excess of the value required for the creation of a deconfined phase is produced in ultrarelativistic Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$=200~GeV. This matter thermalizes rapidly, is strongly interacting, and displays hydrodynamic properties akin to a fluid with very low viscosity. Studies of the interaction of hard scattered partons with this matter provide an important probe of its properties. [Preview Abstract] |
Tuesday, September 20, 2005 2:30PM - 2:45PM |
CC.00002: Measurement of Neutral Pions in $\sqrt{s_{NN}}$ = 200 GeV Cu+Cu Collisions with the PHENIX Experiment at RHIC Stefan Bathe The suppression of high-$p_T$ hadrons in central Au+Au collisions has been one of the most significant results at RHIC. It has been attributed to energy loss of partons as they traverse the hot and dense medium created in the collision. It is of interest at which system size the suppression commences. This can be and has been studied by varying the centrality of the collision. A continuous increase of the suppression with increasing centrality has been observed with no indication of a sudden onset. A more precise way to measure the system-size dependence of the suppression is to study the particle production in a lighter system like Cu+Cu. In particular, this permits measurement of particle production for a system with different medium properties as compared to Au+Au, even at the same number of underlying binary nucleon-nucleon collisions. In the 2005 run, PHENIX sampled a total of 3.06 nb$^{-1}$ Cu+Cu collisions at $\sqrt{s_{NN}}$ = 200 GeV, providing the possibility of comparing particle production at high $p_T$ in Cu+Cu and Au+Au. The PHENIX result on neutral pion production in Cu+Cu will be presented. [Preview Abstract] |
Tuesday, September 20, 2005 2:45PM - 3:00PM |
CC.00003: Neutral pion production in $\sqrt{s_{NN}}$=200GeV Au+Au collisions at RHIC-PHENIX Tadaaki Isobe The suppression of neutral pions at high transverse momentum in central Au+Au collisions compared to the yield in p+p collision scaled by the number of underlying nucleon-nucleon collisions in Au+Au has been one of the most intriguing observations at RHIC. The observed suppression is interpreted as a consequence of the energy loss of initially hard-scattered partons traversing the hot and dense matter produced in central Au+Au collisions. In Run 4 PHENIX recorded the integrated luminosity of 0.24 nb$^ {-1}$ of $\sqrt{s_{NN}}$=200 GeV Au+Au collisions, which allows us to extend the measurement of neutral pions to high transverse momentum. We present the PHENIX Run 4 results on neutral pion production in $\sqrt{S_{NN}}$=200GeV Au+Au collisions. [Preview Abstract] |
Tuesday, September 20, 2005 3:00PM - 3:15PM |
CC.00004: Measurement of Direct Photons in $\sqrt{s}$=200GeV p+p Kensuke Okada Direct photon measurements in p+p collisions provide a superb test of the precision of perturbative QCD, because the dominant partonic process for direct photon production is gluon-quark scattering and no hadronic fragmentation process is involved. Direct photons are also expected to be a good probe of the proton gluon-spin structure which can be accessed in polarized-proton collisions at RHIC. With its high-granularity electromagnetic calorimeter, the PHENIX experiment is well suited to identify backgrounds of hadronic decay. The high energy photon trigger plays an important role. In addition, along with the charged tracking system, we can do a photon isolation test, which direct photon events are supposed to pass. In this talk, we will present the direct photon cross section measurement in p+p at mid-rapidity. [Preview Abstract] |
Tuesday, September 20, 2005 3:15PM - 3:30PM |
CC.00005: Measurement of Direct Photons in $\sqrt{s_{NN}}$=200GeV d+Au Collisions at RHIC-PHENIX Hisayuki Torii The measurement of direct photon production at large transverse momentum in hadron interactions is a good test of QCD. Because the direct photon production in Au+Au collisions happens through the fundamental interactions of partons in Au-nuclei and do not interact strongly with the surrounding medium, direct photon production is an important probe in the search of the Quark Gluon Plasma. The partons in Au-nuclei are known to have a different behavior than in protons. To understand such nuclear effects on the partons in Au-nuclei, it is crucial to measure direct photons in p+p and d+Au collisions. This analysis uses the PHENIX electromagnetic calorimeters and triggering system for the detection of photons at high $p_T$. In this talk, we will present the invariant yield of direct photons in $\sqrt{s_{NN}}$=200GeV d+Au collisions at PHENIX. We will present comparison with results in p+p collisions and prediction of a pQCD calculation. We also want to show the centrality dependence of direct photon production in d+Au collisions. [Preview Abstract] |
Tuesday, September 20, 2005 3:30PM - 3:45PM |
CC.00006: Photon Production in $\sqrt{s_{NN}}$=200GeV Au+Au collisions measured by the PHENIX experiment at RHIC Takao Sakaguchi It has been an intriguing result that the yield of high $p_T$ hadrons is suppressed in central Au+Au collisions where a hot and dense medium is supposed to be created. The recent photon measurement from PHENIX has shown that the excess of direct photons at high $p_T$, originating from initial state processes, over decay-photons from known hadronic sources is consistent with a NLO pQCD calculation scaled by the number of binary nucleon-nucleon collisions. The result confirmed that the suppression of high $p_T$ hadrons is due to a final state interaction of hard scattered partons and the medium. Under existence of the medium, various photon contributions are expected at high to intermediate transverse momentum on top of initial process, such as jet-photon conversion, bremsstrahlung and thermal radiation. PHENIX recorded the integrated luminosity of 0.24 nb$^{-1}$ in $\sqrt{s_{NN}}$=200GeV Au+Au collisions in RHIC Run-4, which allows us to reduce uncertainties in the $p_T$ region where the above processes become prominent. In this talk, photon contributions from various processes will be discussed based on the latest photon measurement. [Preview Abstract] |
Tuesday, September 20, 2005 3:45PM - 4:00PM |
CC.00007: Single electron measurement from heavy flavor decays in d+Au and Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV Fukutaro Kajihara The heavy quark measurement has an important role in the investigation of extremely hot and dense matter created in relativistic heavy ion collisions. The heavy quark production may be affected by final state interactions such as their energy loss in the dense medium. On the other hand, the energy loss is predicted to be smaller than that of light quarks with high transverse momentum due to their heavy mass. The measurement of heavy quarks may indicate the flavor dependence of energy loss. For precise heavy quark measurements, the evaluation of conventional cold nuclear effects is essential. In the relativistic p+p and p+A collisions, we can study those effects since high energy density matter is not formed. Measured inclusive electrons can be categorized into two groups. The first group consists of ``photonic'' electrons mainly from $\pi^0$ and $\eta$ Dalitz decays and photon conversion. The second is termed ``non-photonic'' electrons. The semi-leptonic decays of charm and beauty are the dominant sources of the second group. We present the non-photonic electron measurement in the d+Au and Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV by the RHIC-PHENIX experiment. [Preview Abstract] |
Tuesday, September 20, 2005 4:00PM - 4:15PM |
CC.00008: Fragmentation function and partonic kT at $\sqrt{s_{NN}}$=200 GeV Jan Rak Measurements of modifications to jet properties gives detailed information on the interactions of the outgoing parton with the dense nuclear medium and thereby on the nature of the QCD matter produced in heavy-ion collision. The method of leading high-pT particle azimuthal correlations is used for an analysis of the fragmentation function properties, parton intrinsic momentum kT and jet transverse fragmentation momentum jT in pp, CuCu and AuAu collisions at $\sqrt{s_{NN}}$=200 GeV. The sensitivity of combined analysis of single-inclusive and high-pT trigger associated pT distributions to the relative abundance of quark and gluon jets will be discussed. [Preview Abstract] |
Tuesday, September 20, 2005 4:15PM - 4:30PM |
CC.00009: Study of hadronic jet shape modification in hot QCD matter with the PHENIX detector at RHIC Paul Constantin It is a well established fact now that the hot QCD medium formed in central AuAu collisions at $\sqrt{s_{NN}} = 200$ GeV at RHIC suppresses the high transverse momentum hadrons from jets by inducing gluon radiation. Preliminary results on the angular distribution of hadrons within jets obtained via di-hadron correlations also show strong modifications of jet shapes due to the interaction with this medium. We present a high precision study of hadronic jet shape parameters in AuAu collisions with the di-hadron azimuthal correlation method in the intermediate (1-7GeV/c) transverse momentum region. [Preview Abstract] |
Tuesday, September 20, 2005 4:30PM - 4:45PM |
CC.00010: Study of Jet Fragmentation Using High-$p_{T}$ Photon Triggered Events in PHENIX Matthew Nguyen In high-energy, central Au+Au collisions it is well-known that the $p_{T}$ distribution of hadrons associated with jet fragmentation is modified with respect to p+p collisions. The $p_{T}$ distribution of photons produced in hard collisions, however, is not modified. Using the presence of a high-$p_{T}$ direct photon to identify hard collisions, we have obtained a sample of jets in a manner which is not biased by the mechanism which alters the hadron spectrum. We discuss a method for tagging direct photons in the PHENIX detector. We present distributions of jets properties indirect photon-tagged Au+Au, Cu+Cu, and p+p collisions and theirdependence on centrality and reaction plane orientation. [Preview Abstract] |
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