Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session B13: Mini-symposium: Heavy Flavor Production at RHIC |
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Sponsoring Units: DNP Chair: Saskia Mioduszewski, Brookhaven National Laboratory Room: Marriott Tampa Waterside Room 12 |
Saturday, April 16, 2005 10:45AM - 11:21AM |
B13.00001: Heavy Flavor Production at RHIC Invited Speaker: The measurement of charm and beauty production in relativistic heavy ion collisions is both an extreme experimental challenge and rich with physics information. While charmonium production was measured in great detail at the CERN-SPS, the level and dynamics of charm production itself remained unknown. For the first time, the high center-of-mass energy provided by the Relativistic Heavy-Ion Collider (RHIC) at BNL moves the study of heavy quark production in heavy ion collisions into the realm of possibility. The study of heavy flavor production in conjunction with the measurement of charmonia allows us to infer information about the conditions (temperature, density, pressure) in the early phase. Final state effects, such as charmonium suppression, heavy quark energy loss in the medium and initial state effects such as shadowing can be studied by comparison of their yields and spectra in pp, pA and AA collisions. At RHIC quarkonia and open charm production can be measured in various way: open charm and beauty through the measurement of single lepton spectra, the direct measurement of charm mesons (D) through their hadronic decay channels, and hidden charm and beauty through the study of charmonium and bottonium via their decay into dimuons and dielectrons. In this talk I will summarize the current status of heavy flavor measurements at RHIC. Although these studies are just starting they already hint at exciting and novel physics. [Preview Abstract] |
Saturday, April 16, 2005 11:21AM - 11:33AM |
B13.00002: Charm study via electron hadron azimuthal correlations Sotiria Batsouli PHENIX data on single electron production in central and minimum bias Au + Au collisions at $\sqrt{s_{NN}}$ = 130 and 200 GeV indicate an excess of electrons over known light hadronic sources that has been attributed to open charm. The electron data from open charm decay are consistent with two different scenarios. One is the creation of a medium completely transparent to heavy quarks. The other is the creation of a highly opaque medium with the heavy quarks rescattering and hadronizing in the system. If the excess electrons do indeed come from open charm then one would expect a peak near the electron direction in the azimuthal correlation between electrons and hadrons originating from semileptonic decays of the D mesons. In addition, if the medium is transparent to heavy quarks then a clear back-to-back correlation between the electrons and charm jet hadrons is expected, independent of system size. However if the medium is highly opaque then such away-side correlation would not be expected in Au-Au central collisions. Current status of this analysis for p-p, d-Au $\sqrt{s_{NN}}$ = 200 GeV PHENIX data will be presented. [Preview Abstract] |
Saturday, April 16, 2005 11:33AM - 11:45AM |
B13.00003: Preliminary Results on Open Charm Production in Au+Au Collisions at $\sqrt{s_{NN}}$=200 GeV Haibin Zhang Heavy quarks are important tools to probe the hot and dense matter produced in relativistic heavy ion collisions. Due to the large mass of the charm quark, charm cross sections are calculable via pQCD and their yield is sensitive to the initial gluon density. In addition, the open charm yield is an important baseline for understanding the $J/\psi$ production in the presense of deconfined quarks and gluons. We will report preliminary results on open charm production directly reconstructed via hadronic decay channels in minimum bias Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV at the STAR detector. The invariant mass spectra of open charm hadrons will be shown. Their yields will be presented and compared to those in d+Au collisions at $\sqrt{s_{NN}}$=200 GeV. Possible physics implications of these measurements will also be discussed. [Preview Abstract] |
Saturday, April 16, 2005 11:45AM - 11:57AM |
B13.00004: $J/\psi$ polarization study at $\sqrt{s_{NN}}=200$ GeV Au+Au collision of PHENIX experiment Hai Qu The polarization of quarkonium is typically measured via the angular distribution of its decay leptons. This measurement provides a critical test of the quarkonium production mechanism. There were about $1.5 \times 10^9$ Au+Au minimum bias events collected by the PHENIX experiment in Run-4. The estimated number of $J/\psi$ particles to be identified from the PHENIX muon arm data is more than one order of magnitude larger than the $J/ \psi$ samples from Run-2. Due to the limited $J/\psi$ statistics from even this much large data set, very accurate event-by-event acceptance corrections are required to extract quantitative polarization from the data. The current status of this study for PHENIX Run-4 Au+Au data is presented here. [Preview Abstract] |
Saturday, April 16, 2005 11:57AM - 12:09PM |
B13.00005: Nuclear modification of electrons from heavy flavor decays at RHIC Jamil Egdemir Heavy quarks, such as charm and beauty, are an important tool used in the study of nuclear collisions. Initially created by the hard scattering of partons, some of the heavy quark-antiquark pairs dynamically evolve into quarkonia. However, the vast majority hadronizes into particles carrying open heavy flavor, which can decay into semileptonic channels. The PHENIX experiment has measured electrons from heavy flavor decays in p+p and Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. The integrated electron yields are observed to scale with the number of binary collisions. The nuclear modification factor $R_{AA}$, determined from momentum spectra measured in p+p and Au+Au collisions, should shed some light on the question of heavy quark energy loss in the hot and dense medium created in nuclear collisions at RHIC. [Preview Abstract] |
Saturday, April 16, 2005 12:09PM - 12:21PM |
B13.00006: Heavy flavor production in p+p collisions at $\sqrt{s} = 200$ GeV Sergey Butsyk Heavy flavor particles carrying charm or beauty quarks play an important role in understanding the physics of high energy hadronic collisions. Measurement of heavy flavor production in p+p collisions at $\sqrt{s} = 200$ GeV not only provides an important baseline for studying potential nuclear modifications of heavy flavor production in nucleus-nucleus collisions but also tests the applicability of perturbative QCD theory. The unique electron identification capabilities of the PHENIX detector at RHIC allow to measure semi-leptonic decays of heavy flavor particles. Using p+p data collected in the 2001 run, we have measured single electron inclusive $p_T$ distributions. The contribution from heavy flavor decays can be extracted by two independent methods. The ``Converter'' method uses a special data set where the photonic component of the inclusive electron spectrum is enhanced by adding a photon converter to the standard experimental setup. In the ``Cocktail'' method the contributions from Dalitz decays, other light hadron decays, and photon conversions are calculated and subtracted from the inclusive electron spectrum. The final results will be presented. [Preview Abstract] |
Saturday, April 16, 2005 12:21PM - 12:33PM |
B13.00007: Measurement of heavy quark production through the semi-leptonic decay channel in d+Au and p+p collisions at RHIC Weijiang Dong We present preliminary results of electron/positron $p_{T}$ spectra from semi-leptonic decays of heavy quarks in d+Au and p+p collisions at $\sqrt{s_{NN}}$ = 200~GeV. The measured $p_{T}$ ranges from 1.5~GeV/c to 11.5~GeV/c for p+p and to 13.5~GeV/c for d+Au collisions. Implications on the charm and bottom production cross section will be discussed. Status of the analysis of RHIC RUN 4 Au+Au 200~GeV data will also be presented. [Preview Abstract] |
Saturday, April 16, 2005 12:33PM - 12:45PM |
B13.00008: Single Muon Production at Forward Rapidity in p+p Collisions at $\sqrt{s_{NN}}$ = 200GeV Donald Hornback The suppression of quarkonium production is predicted as one of the characteristics of a potential phase transition of nuclear matter from confined to deconfined quarks and gluons. Charm and beauty quark production in p+p collisions is sensitive to the initial conditions prevailing in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC). Heavy flavor quark production may be studied via semi-leptonic decay of D and B mesons into muons. The measurement of heavy quark production provides a baseline for disentangling initial state effects, such as initial gluon density, from final state effects, such as color screening and recombination, which are expected to be present in a deconfined medium. The extraction of an open charm cross-section is also essential in establishing a baseline for total charm production used to normalize charmonium production. PHENIX detectors measure muons at 1.2 $<\vert $\eta$\vert $ $<$ 2.4, enabling the study of open charm production at forward rapidity. The current status of single muon studies for Run-4 p-p data by the PHENIX collaboration is presented. [Preview Abstract] |
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