Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session EF: Heavy Flavor in Relativistic Heavy Ion Collisions |
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Chair: Michael Tannenbaum, Brookhaven National Laboratory Room: Simmons Ballroom 4 |
Friday, October 24, 2008 4:00PM - 4:12PM |
EF.00001: Study of $J/\psi$ production at low $p_T$ in Cu+Cu collisions at $\sqrt{s_{NN}}=200$ GeV at STAR experiment Daniel Kikola $J/\psi$ production in Cu+Cu collisions at $\sqrt{s_{NN}}=200$ GeV has been measured by STAR experiment at RHIC. Cu+Cu is particularly interesting because it is positioned between d+Au where only cold nuclear matter effects are present and Au+Au where significant suppression due to hot nuclear matter was reported. In this talk the study of $J/\psi$ production at low $p_T$ in Cu+Cu at $\sqrt{s_{NN}}=200$ GeV will be reported. The $J/\psi$ invariant yield and nuclear modification factor as a function of transverse momentum (up to 5 GeV/c) and centrality will be presented. The results of $J/\psi$ in Cu+Cu will be compared to relevant p+p data, PHENIX Cu+Cu measurement and various theoretical models. [Preview Abstract] |
Friday, October 24, 2008 4:12PM - 4:24PM |
EF.00002: Fast hadronization of charm, bottom and strange flavor in strangeness rich QGP Johann Rafelski, Inga Kuznetsova We study QGP hadronization at a given $b$ bottom, $c$ charm and $s$ strange quark content conserving entropy. We evaluate the final yields of charm and bottom flavored hadrons within statistical hadronization model. In fast hadronization at fixed reaction volume the high strangeness $s$ and entropy $S$ content of QGP leads to chemical non-equilibrium condition among final state charm and bottom hadrons. We predict a significant increase of their yield, compared a slow (chemical equilibrium) hadronization. Yields of hadrons with two heavy quarks, including $J/\Psi$, decrease compared to expectations since charm (bottom) is `used up' in strange hadron formation. This provides a new powerful mechanism of $J/\Psi$ and $\Upsilon$ suppression. The yield of light hadrons without strangeness depends mainly on the temperature $T$ of hadronization and the related light quark fugacity $\gamma_q$. However the ratio of non-strange to strange hadrons always decreases with increasing of $s/S$. [Preview Abstract] |
Friday, October 24, 2008 4:24PM - 4:36PM |
EF.00003: $\Upsilon$ production in STAR Pibero Djawotho The production of heavy quarkonia states in p+p, p+A and A+A collisions provide an important tool to study the properties of Quark-Gluon Plasma. Their suppression pattern can be used as a thermometer to the QCD matter and henceforth the study of $\Upsilon$ production is of paramount importance. With the completion of the STAR Electromagnetic Calorimeter and with the increased luminosity provided by RHIC in Run 6 and 7, the study of $\Upsilon$ production via the di-electron channel becomes possible. We present the results on $\Upsilon$ measurements in p+p collisions (from Run 6) along with the preliminary results from Au+Au collisions (in Run 7) at $\sqrt{s_{\rm{NN}}} = 200$ GeV from the STAR experiment. [Preview Abstract] |
Friday, October 24, 2008 4:36PM - 4:48PM |
EF.00004: Measurement of Electron-Muon Correlations from Semi-Leptonic D Decay in 200 GeV p+p Collisions at RHIC-PHENIX Tatia Engelmore Charm production is a valuable probe of the early stages of a heavy ion collision. Correlated electron-muon pairs are a signature of semi-leptonic D decays, and a measurement of D mesons provides information on charm quark energy loss in the hot medium. The energy loss of heavy quarks is still not fully understood, so it is vital to investigate different decay channels of charm mesons to better understand this process. Measurements of electron-muon pairs suffer less from background than $e^{+}$$e^{-}$ or $\mu^{+}$$\mu^{-}$ pairs since neither thermal production, Drell-Yan production, nor resonance decays produce this type of correlated signal. This talk will present the analysis of $e-\mu$ pairs in data taken during the 2006 RHIC run of p+p collisions at 200 GeV. It will be shown that a clear back-to-back peak exists in the azimuthal angular distribution of the pairs, indicating charm production. It will also be shown that background sources are small relative to this measurement. The study of electron-muon pairs in p+p collisions provides an important baseline and the first step towards the study of this process in d+Au and Au+Au collisions. [Preview Abstract] |
Friday, October 24, 2008 4:48PM - 5:00PM |
EF.00005: Non-photonic electron identification in the EEMC with the STAR detector Naresh Subba, Bryon Anderson, Wei-Ming Zhang We report on progress to identify non-photonic electrons in the extended pseudo-rapidity range $\eta $ =1.1 to 1.5 and transverse momentum pT= 1.5 to 6.0 GeV/c possible with the end-cap electromagnetic calorimeter (EEMC) with the STAR detector system at RHIC. This identification will enable one to extract double differential electron distributions in order to help study open charm production in proton-proton interactions. In order to extract non-photonic electrons it is necessary to determine electron purity and photonic background removal efficiency. Backgrounds from both hadronic and photonic contributions are identified. The hadrons can be identified by the difference in energy deposition. The photonic contributions arise mainly from two sources, one from gamma conversion and the other from the (Dalitz) decay of mesons. Both processes can be identified from the observation of opposite-sign electron-positron pairs with low invariant mass. Detection efficiencies of photonic electrons can be obtained with Monte-Carlo simulations. [Preview Abstract] |
Friday, October 24, 2008 5:00PM - 5:12PM |
EF.00006: Azimuthal angular correlations between non-photonic electrons and charged hadrons from $p+p$ collisions at $\sqrt{s_{NN}}$ = 200 GeV in RHIC-STAR Shingo Sakai Heavy quarks, charm and bottom, are believed to be produced mostly via initial gluon fusion in nuclear collisions at RHIC. Heavy quark propagation through the hot and dense medium created in heavy ion collisions probes the properties of the medium. Recently a large suppression of non-photonic electrons up to a $p_{T}$ of 10 GeV/$c$ from central Au+Au collisions has been reported by STAR and PHENIX. Since both charm and bottom quarks contribute to non-photonic electron yields through semi-leptonic decays and their relative contributions are expected to be $p_{T}$ dependent, it is important to experimentally determine the charm and bottom quark contributions separately. We will present azimuthal angular correlations between non-photonic electrons and charged hadrons from $p+p$ collisions at $\sqrt{s_{NN}}$ = 200 GeV in RHIC-STAR. The azimuthal angular correlations can be useful to estimate the relative D and B contributions, since the near-side correlation function width will be larger in the semi-leptonic decay of a B meson compared to a D meson, due to the larger mass of the b quark. The shapes of the correlation function at each $p_{T}$ are fit with PYTHIA calculations and the relative contribution of B meson decay to the non-photonic electron yields has been extracted as a function of electron pT up to 9 GeV/c. Implications on bottom quark energy loss in the hot and dense medium will also be discussed. [Preview Abstract] |
Friday, October 24, 2008 5:12PM - 5:24PM |
EF.00007: Non-photonic electron-hadron azimuthal correlation for $\sqrt{s_{NN}}$=GeV\,200 AuAu collisions at STAR/RHIC Bertrand Biritz STAR's measurements on di-hadron correlations in Au+Au and Cu+Cu have shown a suppression of high-pt hadron yields and modifications in the azimuthal correlation. This modified correlation function suggests a broadening on the away-side. A similar pattern has been observed in the correlation triggered by non-photonic electrons, which represent the directions of heavy quarks. Study of the particle emission pattern in the dense QCD medium will provide insight on the mechanism responsible for the pattern and the flavor dependence. This talk will present preliminary STAR results of azimuthal correlations between non-photonic electrons and hadrons in Au+Au at $\sqrt{s_{NN}}$=GeV 200 and compare them to results for Cu+Cu at $\sqrt{s_{NN}}$=GeV 200. This comparison allows one to study the system-size dependence of heavy quark energy loss and emission broadening of its associated particles. [Preview Abstract] |
Friday, October 24, 2008 5:24PM - 5:36PM |
EF.00008: Azimuthal Correlations of Electrons from Heavy Flavor Decay with Hadrons at PHENIX Anne Sickles One unexpected recent result from heavy-ion collisions is the large suppression and elliptic flow of electrons from heavy flavor decay. Further measurements of properties of electrons from heavy flavor decay are crucial to understanding the origin of this suppression and heavy flavor measurements are expected to be sensitive to the properties of the produced matter. We study the azimuthal correlations between electrons from heavy flavor decay and hadrons. Two particle correlations have been used extensively to study the propagation of hard partons through the produced matter in heavy-ion collisions. We apply techniques developed for direct photon-hadron correlations to statistically subtract correlations of electrons arising from Dalitz decays and photon conversions from the inclusive electron-hadron correlations and we present the current status of two-particle correlations between electrons from heavy flavor decay and charged hadrons in Au+Au collisions in the PHENIX experiment. [Preview Abstract] |
Friday, October 24, 2008 5:36PM - 5:48PM |
EF.00009: D-Meson Measurements in Cu+Cu Collisions at $\sqrt{s}$ = 200GeV at STAR Using the Silicon Inner Tracker Sarah LaPointe Since the most likely production mechanism for charm is gluon fusion, the charm cross section should scale with the number of binary collisions. Such a scaling would indicate that the production of charm occurs during the early stages of the collision, making it a unique probe of the partonic matter. Recent measurements provide some insight of the heavy flavor spectrum and collectivity. Non-photonic single electron p$_{T}$ distributions measured in p+p, d+Au, and Au+Au collisions indicate the nuclear modification factor is significantly below unity for p$_{T}$ 1-4 GeV/c for central events. This implies the heavy flavor spectrum is modified by the medium. However, due to an uncertainty in the relative fraction of charm and bottom, this measurement does not enable an unambiguous determination of energy loss that charm experiences in the medium. The event mixing technique has also been used to reconstruct D$^{0}$. However it does not provide the statistical significance necessary to perform a good measurement of charm elliptic flow. In this talk, we present preliminary results from D-Meson measurements in minimum bias Cu+Cu collisions at $\sqrt{s}$=200GeV at STAR. The measurements are performed using a secondary vertexing technique. They provide a basis for future measurements of charm cross section, energy loss and collectivity in heavy ion collisions at RHIC. [Preview Abstract] |
Friday, October 24, 2008 5:48PM - 6:00PM |
EF.00010: Open Charm Production in $\sqrt{s_{NN}}=200 GeV$ Cu+Cu collisions at Forward Rapidities Irakli Garishvili Open charm production is an important probe of the strongly interacting matter created during the early stages of heavy ion collisions. Single muons are used to tag open charm production via semileptonic decays of D-mesons. The PHENIX detector at RHIC is used to measure single muon production at forward and backward rapidities over the range of $1.1 > | \eta | > 2.25$. PHENIX has previously measured single muon production for p+p collisions at $\sqrt{s_{NN}}=200 GeV$, which is used as a baseline measurement for calculating the Nuclear Modification Factor ($R_{AA}$) for heavy ion collisions. The status of the first measurement in Cu+Cu collisions at $\sqrt{s_{NN}}=200 GeV$ of single muon cross sections and nuclear modification factors as a function of transverse momentum will be presented. [Preview Abstract] |
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