Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session C9: Ultrarelativistic Heavy Ions: Quarkonia, Heavy Flavor |
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Sponsoring Units: DNP Chair: Richard Seto, University of California, Riverside Room: Governor's Square 11 |
Saturday, April 13, 2013 1:30PM - 1:42PM |
C9.00001: Free energy and potential energy of static quark anti-quark pair at T$>$0 Peter Petreczky I will discuss lattice QCD calculations of the free energy and the potential energy of static quark anti-quark pair at non-zero temperature using highly improved staggered quark (HISQ) action. The free energy of static quark anti-quark pair is calculated from the correlation functions of Polyakov loops, while the potential energy is extracted from the analysis of temporal Wilson loops with time extent $\tau<1/T$. I will show that chromo-electric screening effects are not visible in the potential energy for distances $r<1$ fm and temperatures $T<200$ MeV, and the temperature dependence of the free energy can be understood in terms of hadronic degrees of freedom. I will also discuss the implication of these findings on quarkonium properties in quark-gluon plasma. [Preview Abstract] |
Saturday, April 13, 2013 1:42PM - 1:54PM |
C9.00002: Quarkonium formation and melting at LHC energies Edwin Norbeck, Yasar Onel The $b\bar{b}$ ($\Upsilon$) mesons appear to be produced in the initial PbPb collision at 2.76 TeV per nucleon pair followed by partial melting in the hot quark-gluon plasma. In sharp contrast, the $c\bar{c}$ ($J/\Psi$) mesons seem more likely to be formed by recombination at the hadronization stage. Is the difference caused by there being many more c quarks formed than b quarks? It will be interesting to see the results of collisions at 5.5 TeV per nucleon pair for which the number of b quarks will be larger. The $B_{c}$ mesons, with one quark of each kind are seldom seen in pp collisions because a particle-antiparticle pair requires the simultaneous production of four heavy quarks. Although a family of $B_{c}$ mesons have been predicted, only the ground state has been seen. If the $c\bar{c}$ mesons are produced by recombination, it could be expected that $B_{c}$ mesons would be abundant with PbPb. Because the quark and antiquark have different flavor the $B_{c}$ are long lived, 0.45 ps (to be compared with about 1.5 ps for the lighter $B$ mesons). They would be seen with PbPb reactions by $B_{c}^{\pm} \rightarrow J/\Psi (\mu^+\mu^-)\pi^{\pm}$ looking at muons and pions from displaced vertices. [Preview Abstract] |
Saturday, April 13, 2013 1:54PM - 2:06PM |
C9.00003: Quarkonia measurements and physics opportunities in $p$+A collisions at the PHENIX experiment. Kwangbok Lee The PHENIX collaboration has measured quarkonia resonances of $J/\psi$, $\psi^{'}$, $\chi_c$ and $\Upsilon$ in $d$+Au collisions. The measurements give us important knowledge to understand the cold nuclear matter effects of nuclear parton modification, gluon saturation, initial state parton energy loss and final state nuclear absorption models. In addition to the quarkonia, measurements of the Drell-Yan process are also good channels to understand the initial-state effects since the leptons from Drell-Yan will not interact with the nuclear medium. Recently installed Silicon Vertex Detectors, FVTX \& VTX, will measure open heavy flavors and Drell-Yan precisely. At RHIC, there are discussions to deliver multi-species $p$+A collisions to get new and interesting physics measurements in near future. In this talk, I review the PHENIX measurements and discuss the physics opportunities with $p$+A collisions by the FVTX \& VTX detectors and with possible detector upgrades for the future. [Preview Abstract] |
Saturday, April 13, 2013 2:06PM - 2:18PM |
C9.00004: Open heavy flavor production in Cu+Au collisions at forward rapidity at $\sqrt{s_{NN}}=200 GeV$ Irakli Garishvili, Sanghoon Lin Open heavy flavor 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 the production of heavy quarks via semileptonic decays of D and B mesons. With its Muon arms, the PHENIX detector at RHIC is optimized to measure muon production from different sources at forward and backward rapidities over the range of $1.2 > | \eta | < 2.2$. PHENIX has already measured the production single muons from open heavy flavor meson decays for several collision systems (Cu+Cu, d+Au and p+p) at $\sqrt{s_{NN}}=200 GeV$. These data indicate that the production of heavy quarks and their subsequent interactions with the medium in forward rapidity kinematic region are strongly modified by both hot and cold nuclear matter effects. In Summer 2012 PHENIX collected large dataset on Cu+Au collisions at $\sqrt{s_{NN}}=200 GeV$, which is the first RHIC data dedicated to colliding two asymmetric heavy ions beams. Studying collisions of asymmetric heavy ions can be crucial in understanding the geometry dependence of initial and final state effects. The status of the first measurement in Cu+Au collisions at $\sqrt{s_{NN}}=200 GeV$ will be presented. [Preview Abstract] |
Saturday, April 13, 2013 2:18PM - 2:30PM |
C9.00005: Heavy quark production at forward and backward rapidity in d$+$Au collisions at $\sqrt{s} = $ 200 GeV Sanghoon Lim Heavy quarks produced in the early stage of heavy ion collisions are very effective probes of dense partonic medium produced at RHIC. PHENIX has an ability to access this information by measuring single electrons in central arm spectrometers (\textbar eta\textbar \textless 0.35) and single muons in forward (backward) muon spectrometers (1.4\textless \textbar eta\textbar \textless 2.0). The measurement of heavy quark production at forward(backward) rapidity from d$+$Au data is crucial for the determination of initial state Cold Nuclear Matter effects in heavy ion collisions. The PHENIX result of single electrons decaying from heavy flavor at mid-rapidity has shown a strong Cronin enhancement in the central d$+$Au collisions. Heavy flavor measurements at forward(backward) rapidity are key measurements to access the low(high) x patron distributions within the Au nucleus. During the data-taking period in 2008, PHENIX collected 30 times more d$+$Au collision data than in the previous 2003 run. The increased luminosity allows studies of the centrality dependence on heavy quark production over an extended kinematic range. In this talk, the measurement of single muons decaying from open heavy flavor quarks at forward and backward rapidity from the 2008 RHIC d$+$Au Run will be presented. [Preview Abstract] |
Saturday, April 13, 2013 2:30PM - 2:42PM |
C9.00006: Intermediate Silicon Tracker for STAR HFT Upgrade Yaping Wang The STAR experiment at the Relative Heavy Ion Collider in Brookhaven National Laboratory at Upton, NY will soon be upgraded with the a Heavy Flavor Tracker (HFT), which will greatly enhance the capability for heavy flavor studies by measurements of displaced vertices and direct topological reconstruction of open charm hadrons. The HFT consists of 4 layers of silicon detectors. The Intermediate Silicon Tracker (IST) is one of these layers. It uses conventional silicon pad sensors, which provide a position resolution of about 180 (1800) microns in the r-phi (longitudinal) direction. The IST detector is in production now so that it will be ready for installation in Fall 2013. In this talk, we will present the design and performance of the IST, and the status of the production. [Preview Abstract] |
Saturday, April 13, 2013 2:42PM - 2:54PM |
C9.00007: Forward Silicon Detector for the PHENIX Experiment Jin Huang The Forward Vertex Detector (FVTX), which provides precision tracking near the collision vertex in the forward direction, was installed in the PHENIX experiment at RHIC. Each of the FVTX arms has full azimuthal coverage. When combined with the VTX silicon detector, it provides rapidity coverage of 1.2 to 2.2, which matches the acceptance of the two existing PHENIX muon spectrometer arms. Each of the two FVTX arms consists of four planes of silicon mini-strips, with 75 $\mu$m pitch in the radial direction and 96 azimuthal segments. In 2012, the detector was successfully commissioned in PHENIX, and physics data were taken in $\sqrt{s}=$510 GeV $p$+$p$ and $\sqrt{s_{NN}}=$200 GeV Cu+Au collisions. The primary observables, detector performance and analysis status will also be presented in this talk. [Preview Abstract] |
Saturday, April 13, 2013 2:54PM - 3:06PM |
C9.00008: Dielectron measurements in $d+Au$ collisions at $\sqrt{s}_{NN}$ = 200 GeV using the PHENIX Detector at RHIC Deepali Sharma Dielectrons are among the most promising probes for studying the early, hot and dense stages created in relativistic heavy-ioncollisions. They are color neutral and so interact only electromagnetically, thus carrying information to the detectors about the conditions and properties of the medium at the time of their creation. The low mass region ($<$1 GeV/$c^2$) consists primarily of pairs from Dalitz decays of light hadrons and direct decays of vector mesons that can be modified in the medium, while the intermediate (1-3 GeV/c$^2$) and high (4-8 GeV/c$^2$) mass regions are dominated by correlated pairs originating from open charm and beauty respectively. PHENIX measured a large, unexpected enhancement in Au+Au collisions in the low mass region (0.2-0.8 GeV/c$^2$), with respect to the baseline cocktail scaled from p+p collisions. Current theories are unable to explain this excess, and a natural question to ask would be to check for any cold nuclear matter effects in the initial state of the collision. During the 2008 RHIC run, PHENIX collected a large data set of d+Au collisions that allowed a look into the high mass region, thereby providing the characteristics of heavy flavor production. This talk will show the results of dielectron measurements in the d+Au collisions. [Preview Abstract] |
Saturday, April 13, 2013 3:06PM - 3:18PM |
C9.00009: Measurement of Dielectron Spectra with the Hadron Blind Detector in PHENIX Jiayin Sun Dielectrons are an important color neutral probe for studying the evolution of the hot dense medium created by heavy ion collisions at RHIC. At low mass region, dielectron spectra consists mainly of direct photons and light vector mesons, and give insight on the earliest stages of the collisions and thus constrain theoretical models on thermalization and chiral symmetry restoration in heavy ion collisions. At intermediate and high mass region, there are significant contributions from charm and bottom. The region was utilized to measure cross sections of open charm and open bottom, as well as quarkonium suppression. The measurement of the dielectron spectra, however, suffers from an unfavorable signal to background ratio. Random combination of electron positron pairs from unrelated sources, mostly Dalitz decay of $\pi$0 and external conversion of decay photon to electrons, are the main contributor to the background. The Hadron Blind Detector, a windowless proximity focusing Cerenkov detector, is designed to reduce this background by identifying electron tracks from photon conversions and $\pi$0 Dalitz decays. The detector has been installed and operated in PHENIX in 2009 and 2010, where Au+Au and reference p+p data sets were taken. Results from these data sets will be presented. [Preview Abstract] |
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