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 BF: RHIC: p-p, d-Au, and Cu-Cu |
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Sponsoring Units: DNP JPS Chair: Brant Johnson, Brookhaven National Laboratory Room: Ritz-Carlton Hotel Plantation 3 |
Monday, September 19, 2005 7:00PM - 7:15PM |
BF.00001: The excess of positive charged particles measured at forward rapidities in d+Au collisions and baryon transport Ramiro Debbe The difference between positive and negative hadronic yields, measured by BRAHMS in d+Au at $\eta=3.2$ (1), has been identified as a challenge to partonic descriptions based on pQCD (2). Within such descriptions, the hadronic yields are dominated by pion production, and isospin conservation fixes the abundance of positive and negative pions to be roughly equal. The measured difference was found to be due to a high number of protons up to the highest pt measured (3). To shed additional light on this subject, we studied baryon transport in d+Au by extracting net-proton distributions in eta. A net-proton excess at $\eta = 3.2$ identifies the higher yield of positive particles as ``beam fragments.'' Comparisons to theory are done to elucidate the mechanism that gave these baryons such high pt.\newline (1) R. Debbe for the BRAHMS Collaboration J. Phys. G: Nucl. Part. Phys. {\bf30} S759-S765 (2004).\newline (2) V. Guzey, M. Strikman, W. Vogelsang, Phys. Lett. D {\bf 603}, 173 (2004).\newline (3) R. Debbe for the BRAHMS Collaboration ICPAQGP 2005, nucl-ex/ 0504015. [Preview Abstract] |
Monday, September 19, 2005 7:15PM - 7:30PM |
BF.00002: Measurement of low mass vector mesons by $e^{+}e^{-}$ pairs in $\sqrt{s_{NN}} = 200GeV$ d+Au collisions at PHENIX Yuji Tsuchimoto In-medium modification of low mass vector mesons is predicted if chiral symmetry restoration occurred in the hot/dense matter created by heavy ion collisions at RHIC. The measurement of vector mesons in cold nuclear matter is important not only for a baseline measurement for our understanding of the in-medium effect in Au+Au collisions, but also for improving our understanding of in-medium modification of the meson properties inside the cold matter. The PHENIX detector can measure electrons and hadrons within the same acceptance at mid rapidity. $\omega$ and $\phi$ mesons have both hadronic and leptonic decay modes. Because the electron has a much larger mean free path, it suffers little from the final state effect, therefore he comparison of the effect; therefore the measurement in these two channels will provide us a powerful tool to study the possible in-medium effect due to the chiral symmetry restoration . PHENIX has substantial data sets for p+p, d+Au, Au+Au and Cu+Cu collisions to make a complete study of these effects. The current status of the $\omega$ and $\phi$ analysis will be shown for the d+Au analysis. [Preview Abstract] |
Monday, September 19, 2005 7:30PM - 7:45PM |
BF.00003: Systematic Investigations of Femtoscopic Radii in Heavy Ion Collisions Ron Soltz The technique of femtoscopy has been used for many years to extract radii from multi-particle correlations to characterize the spatio-temporal extent of the emission region in heavy ion collisions. We will present a systematic study of these radii as a function of colliding species, centrality, energy, and orientation for a variety of identified particle correlations over a range transverse and longitudinal momenta. We will highlight a number of simple and elegant trends that reveal much about the nature of particle production in heavy ion collisions. Comparisons to models will be discussed in the context of constraining the equation of state for the matter created in these collisions. Future lines of inquiry will be considered. [Preview Abstract] |
Monday, September 19, 2005 7:45PM - 8:00PM |
BF.00004: $R_{dA}$ measurement with muons from light and heavy flavor decay in $\sqrt{s_{NN}} = 200 GeV/c2$ p-p and d-Au collisions in PHENIX experiment at RHIC Xiaorong Wang The particle production in d-Au collisions at RHIC in the forward and backward directions is sensitive to various nuclear effects. A study of light meson and heavy flavor production in d-Au collisions in various kinematics regions presents an opportunity to probe cold nuclear medium effects - from parton shadowing, Color Glass Condensate to initial state energy loss. The PHENIX muon arms cover both forward and backward directions in the rapidity range of $1.2 < |\eta| < 2.4$, and are in a good position to make such measurements. We investigate nuclear medium effects on light meson and heavy flavor hadron via decay muons in the p-p and d-Au collisions. The current status of this analysis will be presented. [Preview Abstract] |
Monday, September 19, 2005 8:00PM - 8:15PM |
BF.00005: Measurements of the total Cu-Cu Cross Section at RHIC Angelika Drees Using the Vernier Scan or Van der Meer Scan technique, where one beam is swept stepwise across the other while measuring the collision rate as a function of beam displacement, the transverse beam profiles, the instantaneous luminosity and the cross section can be measured. The cross section is an important ingredient when the total delivered luminosity is determined and when the instantaneous luminosity is monitored. The experimental detectors need the cross section to normalize their measurements. Though it can be calculated to some level of accuracy it has never been measured so far. This report presents the measurements and the results from the FY2005 Cu-Cu run. [Preview Abstract] |
Monday, September 19, 2005 8:15PM - 8:30PM |
BF.00006: Measurement of single muons in Cu-Cu collisions with the PHENIX experiment at RHIC DongJo Kim, MinKyung Lee The measurement of open charm production in various collision species at different energies is important to study the properties of matter formed in the early stage of relativistic heavy ion collisions, especially to understand charm energy loss and recombination systematically. The RHIC facility provided Cu-Cu collisions at both high and low energy in 2005. This lighter colliding system compared with Au-Au can give much better precision on the centrality measurement in the lower $N_{part}$ region, and the comparison between two different colliding energies may give us a better systematic understanding of charm production. PHENIX detectors measure muons in the rapidity range $1.2 < | \eta | < 2.4$, thus enabling us to study open charm as well as light meson production at forward rapidity. The status of single muon measurements of the centrality, transverse momentum and rapidity dependence of semi-leptonic open charm decays and light meson production, in Cu+Cu collisions at $\sqrt{s_{NN}}$=200 GeV and 62.4GeV will be presented. [Preview Abstract] |
Monday, September 19, 2005 8:30PM - 8:45PM |
BF.00007: Measurement of vector mesons via di-electrons in Cu+Cu collisions at $\sqrt{s_{NN}}=200$~GeV at RHIC-PHENIX Susumu Oda Measurement of vector mesons via di-leptons is considered to be one of the most promising probes for the early hot dense stages of relativistic heavy ion collisions. The yields of heavy quarkonia are predicted to be suppressed in a deconfined quark gluon plasma due to the color Debye screening. However, the yields will be modified by other competing processes such as recombination, shadowing and heavy quark energy loss. Therefore systematic study of $J/\psi$ production for several system sizes and energy densities is necessary to understand the production and suppression mechanism. The light vector mesons ($\rho$, $\omega$ and $\phi$) are expected to be sensitive to possible in-medium modifications by chiral symmetry restoration. In the RHIC Run-5 starting in January 2005, the PHENIX experiment measured Cu+Cu collisions at $\sqrt{s_{NN}}=200$~GeV. The current status of $J/\psi$, $\phi$ and $\omega \rightarrow e^{+}e^{-}$ analysis in Cu+Cu collision will be presented. [Preview Abstract] |
Monday, September 19, 2005 8:45PM - 9:00PM |
BF.00008: System-size and energy dependence of elliptical flow Richard Bindel Azimuthal correlations are proving to be an extraordinarily powerful tool in elucidating the initial conditions and dynamical evolution of matter created in relativistic heavy ion collisions. As our theoretical vision of heavy ion collisions evolves, differential flow measurements are providing both guidance and strong constraints. This work examines the elliptic flow as a function of pseudorapidity, centrality, transverse momentum, energy, and species. The data presented were taken with the PHOBOS experiment at RHIC during Au-Au and Cu-Cu collisions ranging over an order of magnitude in energy. The implications of these data on the source initial conditions and dynamics will be discussed. [Preview Abstract] |
Monday, September 19, 2005 9:00PM - 9:15PM |
BF.00009: $J/\psi \rightarrow \mu^+\mu^-$ Production in Cu+Cu collisions from the PHENIX Experiment Abigail Bickley Heavy quarkonia provide a sensitive probe of the modification of the QCD confining potential that is expected to occur at high temperatures. As these quark-antiquark states hadronize they interact with the surrounding medium and provide a useful diagnostic for probing the state of matter present in heavy ion collisions. It is predicted that one of the signatures of a deconfined medium is the suppression of heavy quarkonia production due to color screening. However, other competing effects such as shadowing, heavy quark energy loss, and charm recombination influence the charmonium yield as well. In the PHENIX experiment the charmonium yield can be studied through the dimuon channel using the forward muon spectrometers. The $J/\psi$ yields obtained from Cu+Cu collisions will be presented as a function of centrality, transverse momentum, collision energy, and species. [Preview Abstract] |
Monday, September 19, 2005 9:15PM - 9:30PM |
BF.00010: Charged Hadron Transverse Momentum Spectra in Cu+Cu Collisions from PHENIX Carla Vale The observed suppression of high-$p_T$ hadrons at mid-rapidity in central Au+Au collisions at RHIC has generated a high level of interest, since it may be a consequence of the energy loss of hard partons traveling through the hot and dense medium created in these collisions. The understanding of these results can significantly benefit from additional studies of how the high-$p_T$ suppression depends on collision energies and system sizes. During the latest RHIC run, PHENIX collected data on Cu+Cu collisions at $\sqrt{s_{NN}} = 200$~GeV and $\sqrt{s_{NN}} = 62$~GeV, allowing for comparison with both the larger system size collisions in Au+Au and the baseline measurements performed in d+Au and p+p collisions. We present results from PHENIX on the charged hadron transverse momentum spectra in Cu+Cu collisions and its centrality dependence, as well as comparisons with other colliding systems and energies. [Preview Abstract] |
Monday, September 19, 2005 9:30PM - 9:45PM |
BF.00011: Identified charged hadron spectra in Au+Au and Cu+Cu collisions in PHENIX Masaya Oka One of the most significant observations at the RHIC is that unlike mesons, baryons are not suppressed at intermediate $p_T$ (2 - 5 GeV/$c$) region. This has prompted the development of a new theoretical framework,quark recombination, however, the agreement between recombination models and data is still qualitative. The systematic measurement of identified hadron spectra up to large $p_T$ region is crucial for the further understanding of hadron production at RHIC energies. The PHENIX experiment has measured the $\pi^{\pm}$, $K^{\pm}$, $p$, and $\overline{p}$ production in Au+Au collisions at $\sqrt {s_{NN}}$ = 62.4 and 200 GeV and in Cu+Cu collisions at $\sqrt {s_{NN}}$ = 22.5, 62.4 and 200 GeV. These data will be used to study the system size and collision energy dependence of hadron production. In this session, we will present new results on identified charged hadron spectra at large $p_T$ region in $\sqrt{s_{NN}}$ = 62.4 and 200 GeV Au+Au, measured by the Time-of-Flight detector and Aerogel Cherenkov Counter in PHENIX. The latest studies on Cu+Cu collisions in different energies will also be presented. [Preview Abstract] |
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