Session HH: Ultra-relativistic Heavy Ions: Heavy Flavor Production

Chair: Gerd Kunde, Los Alamos National Laboratory
Room: Lamy

 Friday, November 5, 2010 10:30AM - 10:42AM HH.00001: Heavy flavor production in Cu+Cu and p+p collisions at $\sqrt {s_{NN}}$ = 200 GeV Archil Garishvili Heavy flavor production can serve as an important probe of the Quark Gluon Plasma. Single muon production is an important tool for studying heavy flavor production via semi-leptonic decays of open heavy flavor mesons. The PHENIX experiment at RHIC has the ability to detect muons over the range of 1.1 $<$ $\mid\eta\mid$ $<$ 2.25 using two back-to-back muon spectrometers. The first measurement of the nuclear modification factor of open heavy flavor production at forward rapidity in Cu+Cu collisions at $\sqrt{s_{NN}}$ = 200 GeV taken during 2005 run will be described. Also, results concerning heavy flavor production in p+p collisions at $\sqrt {s}$ = 200 GeV will be presented. Friday, November 5, 2010 10:42AM - 10:54AM HH.00002: Towards the Gravity Dual of Quarkonium in the Strongly Coupled QCD Plasma Paul Hohler , Hovhannes Grigoryan , Mikhail Stephanov We build a bottom-up'' holographic model of charmonium by matching the essential spectral data. We argue that this data must include not only the masses but also the decay constants of the $J/\psi$ and $\psi'$ mesons. Relative to the soft-wall'' models for {\em light} mesons, such a matching requires two new features in the holographic potential: an overall upward shift as well as a narrow dip'' near the holographic boundary. We calculate the spectral function as well as the position of the complex singularities (quasinormal frequencies) of the retarded correlator of the charm current at finite temperatures. We further extend this analysis by showing that the residues associated with these singularities are given by the boundary derivative of the appropriately normalized quasinormal mode. We find that the melting'' of the $J/\psi$ spectral peak occurs at a temperature $T\approx 540$ MeV, or 2.8 $T_c$, in good agreement with lattice results. Friday, November 5, 2010 10:54AM - 11:06AM HH.00003: Estimate of the $B$ decay contribution to total $J/\psi$ production at RHIC and the LHC Ramona Vogt , Randy Nelson We assess the theoretical uncertainties on the inclusive $J/\psi$ production cross section in the Color Evaporation Model and compare them to the uncertainties in secondary $J/\psi$ production through $B$ meson decays, $B \rightarrow J/\psi X$, calculated in the FONLL approach. We discuss the importance of the quark mass and the choice of renormalization and factorization scale on the uncertainty estimate. We then construct the uncertainty in the ratio of $J/\psi$ production by $B$ decays to the total $J/\psi$ production and present the results as a function of $p_T$ at mid and forward rapidities for the RHIC and LHC detector acceptances over a range of center of mass energies. Friday, November 5, 2010 11:06AM - 11:18AM HH.00004: Non-photonic Electron Measurements in 200 GeV p+p collisions at RHIC-STAR Xin Li Compared to the light quarks, heavy quarks are produced early in the collisions and interact very differently with the strongly coupled QGP(sQGP) created at RHIC. In addition, their large masses are created mostly from Higgs mechanism. All these features make heavy quark an ideal probe to study the sQGP. One of the critical references in these studies is the heavy quark production in p+p collisions, which also provides a crucial test to the pQCD. Measuring electrons from heavy quark semi-leptonic decay (non-photonic electron) is one of the major approaches to study heavy quark production at RHIC. We will present STAR measurements on the mid-rapidity non-photonic electron production at pT$>$2 GeV/c in 200 GeV p+p collisions using the datasets from the 2008 and 2005 runs, which have different photonic backgrounds. We will compare our measurements with the FONLL prediction and also report the status of the analysis at pT$<$2 GeV/c using the dataset from the 2009 run. Friday, November 5, 2010 11:18AM - 11:30AM HH.00005: Extracting bottom quark production cross section from p+p collisions at RHIC Wenqin Xu The STAR collaboration has measured the non-photonic electron (NPE) production at high transverse momentum ($p_T$) at middle rapidity in $p+p$ collisions at $\sqrt{s}= 200$~GeV at the Relativistic Heavy Ion Collider (RHIC). The relative contributions of bottom and charm hadrons to NPE have also been obtained through electron hadron azimuthal correlation studies. Combining these two, we are able to determine the high $p_T$ mid-rapidity electron spectra from bottom and charm decays, separately. PYTHIA with different tunes and FONLL calculations have been compared with this measured electron spectrum from bottom decays to extract the $b\bar{b}$ differential cross section after normalization to the measured spectrum. The extrapolation of the total $b\bar{b}$ production cross section in the whole kinematic range and its dependence on spectrum shapes from model calculations will also be discussed. Friday, November 5, 2010 11:30AM - 11:42AM HH.00006: Measurement of single electrons from heavy flavor decays in d+Au collisions by PHENIX J. Matthew Durham Measurements of heavy quarks (charm and bottom) produced in relativistic collisions of heavy ions have provided significant insight into the dynamics of the dense partonic matter created at RHIC. The PHENIX detector is well suited to make measurements of these quarks through their semi-leptonic decay channels. By subtracting a cocktail of electrons and positrons from other sources, the contribution from open heavy flavor can be identified. PHENIX measurements of single electrons from Au+Au collisions at 200 GeV have shown significant azimuthal anisotropy in heavy quark emission from the medium, as well as large suppression at high transverse momentum. However, a full interpretation of this data requires quantitative measurements of cold nuclear matter effects, which can be accessed through single electron/positron measurements in d+Au collisions. The status of the measurement of electrons from heavy flavor decays from the 2008 RHIC d+Au Run will be discussed. Friday, November 5, 2010 11:42AM - 11:54AM HH.00007: Open charm hadron reconstruction via hadronic decays in p+p collisions at $\sqrt{s}$ = 200 GeV Yifei Zhang Heavy quarks are believed to be an ideal probe to study the properties of the QCD medium produced in the relativistic heavy ion collisions. Heavy quark production in elementary particle collisions is expected to be well calculated in the perturbative QCD. Precise understanding on both the charm production total cross section and the fragmentation in p+p collisions is a baseline to further investigation of the QCD medium via open charm and charmonium in heavy ion collisions. Early RHIC measurements in p+p collisions which were carried out via semi-leptonic decay electrons provides difficulty in directly relating the kinematics of the electron to that of the heavy quark hadron, the limited momentum coverage and the mixed contribution from various charm and bottom hadrons in the electron approach. In this talk, we will present the reconstruction of open charm hadrons ($D^0$ and $D^*$) via the hadronic decays in p+p collisions at $\sqrt{s}$ = 200 GeV in the STAR experiment. The analysis is based on the large p+p minimum bias sample collected in RHIC in the year 2009. The Time-Of-Flight detector, which covered 72\% of the whole barrel, was used to improve the decay daughter identification. Physics implications from this analysis will be presented. Friday, November 5, 2010 11:54AM - 12:06PM HH.00008: Reconstruction of charmed decays using microvertexing techniques with the STAR Silicon Detectors Jonathan Bouchet Due to their production at the early stages, heavy flavor particles are of interest to study the properties of the matter created in heavy ion collisions. Direct topological reconstruction of $D$ and $B$ mesons, as opposed to indirect methods using semi-leptonic decay channels [1], provides a precise measurement and thus disentangles the $b$ and $c$ quarks contributions [2]. In this talk we present a microvertexing technique used in the reconstruction of $D^{0}$ decay vertex ($D^{0} \rightarrow K^{-}\pi^{+}$) and its charge conjugate. The significant combinatorial background can be reduced by means of secondary vertex reconstruction and other track cut variables. Results of this method using the silicon detector information of the STAR experiment at RHIC will be presented for the Au+Au system at $\sqrt{s_{NN}}$ = 200 GeV. \\[4pt] [1] B. I. Abelev, et al., Phys. Rev. Lett. {\bf 98} (2007) 192301 \newline [2] N. Armesto et al., Phys. Lett. B{\bf 637} (2006) 362-366.