Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session B10: Mini-Symposium on New Results in Heavy Ion Physics |
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Sponsoring Units: DNP Chair: James Nagle, University of Colorado - Boulder Room: Governor's Square 10 |
Saturday, May 2, 2009 10:45AM - 11:21AM |
B10.00001: Creation and evolution of the deconfined Quark-Gluon matter Invited Speaker: Recent results from RHIC have shown evidence for the formation of a deconfined quark-gluon phase of nuclear matter produced in relativistic heavy ion collisions. Certain features, such as the apparent low viscosity of the medium, led theorists to describe the phase as a near perfect liquid. The apparent strong coupling in the parton phase was not anticipated in the framework of pQCD and is presently under further investigation through a multitude of new measurements. I will present some of the latest data from RHIC and discuss them in the context of our understanding of phase characteristics such as thermalization, partonic interaction probability and hadronization mechanisms. In relation to future RHIC measurements and heavy ion collisions at the LHC I will introduce new ideas, based on resonance production in jets, to measure chiral symmetry restoration, which is predicted to be one of the fundamental QCD signatures of the phase transition but which has not yet been verified experimentally. [Preview Abstract] |
Saturday, May 2, 2009 11:21AM - 11:33AM |
B10.00002: Charmonium Cold Nuclear matter effects: Latest results from PHENIX Loren Linden Levy Charmonium suppression in hot and dense nuclear matter has been argued to be a unique signature for the production of the quark gluon plasma (QGP). In order to search for this effect in heavy ion collisions one must have a clear understanding of the modifications present in the charmonium spectrum resulting from the interaction with normal cold nuclear matter. The PHENIX experiment has measured J/$\psi$'s spectrum from deuteron-gold (d-Au) interactions at $\sqrt{s}$=200GeV and compared these with a proton-proton baseline (2006 RHIC run) in order to constrain these cold nuclear matter effects. We will present the latest analysis from the 2008 RHIC run, with an integrated luminosity of ~80 nb$^{-1}$, compared to the 2.4 nb$^{-1}$ collected in the 2003 RHIC run. [Preview Abstract] |
Saturday, May 2, 2009 11:33AM - 11:45AM |
B10.00003: $J/\psi$ Production and $R_{AA}$ at Forward Rapidities in Run 7 $\sqrt{s_{NN}}$=200GeV Au+Au Matthew Wysocki $J/\psi$ suppression is an important observable for verifying our understanding of the QGP formed in relativistic heavy ion collisions. In particular, the suppression as a function of transverse momentum has been of particular interest recently. Theoretical predictions remain diverse due to our imprecise knowledge of charm production mechanisms, nuclear effects, and suppression and regeneration processes. Because of this, it is important to measure this rare process in a variety of channels, observables, and phase space regions. We will show the latest results for $J/\psi$ production and $R_{AA}$ at forward rapidities in the PHENIX Muon Arms, as functions of centrality, rapidity and $p_T$, using the recent higher-statistics datasets for both Au+Au and p+p to improve our measurements over previous results. [Preview Abstract] |
Saturday, May 2, 2009 11:45AM - 11:57AM |
B10.00004: Baryon resonance yields after QGP hadronization Inga Kuznetsova, Johann Rafelski We study the yields of $\Delta$(1232), $\Sigma$(1385) and $\Lambda$(1520) baryon resonances in the framework of a kinetic master equations for the case of entropy rich QGP fast hadronization leading to initial above chemical equilibrium yields of hadrons. In this case the resonance yield in a rapidly expanding system does not follow the chemical equilibrium yield as function of time. We find that a significant additional yields of $\Delta$(1232), $\Sigma$(1385) can be produced by the back-reaction of the over- abundance of the decay products of resonances. A more complex situation arises for a relatively narrow resonance such as $\Lambda$(1520), which can be in part seen as a stable state, which is depopulated to increase the heavier resonance yield. We find that a suppression of yield of such resonances, as compared to statistical hadronization model, is possible. The pattern of deviation of hadron resonance yields from expectations based on statistical hadronization model are another characteristic signature for a fast hadronization of entropy rich QGP. The total yields of the ground state baryons used in analysis of data (such as N, $\Lambda$) are not affected. The results are in agreement with yields of these resonances reported by RHIC experiments. [Preview Abstract] |
Saturday, May 2, 2009 11:57AM - 12:09PM |
B10.00005: Rapidity dependency of (Anti)-deuteron Coalescence in Au-Au collisions Michael Murray The coalescence of protons and neutrons into deuterons is sensitive to the space-time extent of the baryon freeze-out region. The coalescence parameter and the phase space density recast the information contained in the proton and deuteron spectra into ``chemical" and ``dynamic" terms. The phase space density is sensitive to the chemical potential and the temperature of the system. The coalescence parameter $B_2$ can be interpreted in terms of a ``volume of homogeniety" which depends upon the temperature of the system and the radial flow. The large rapidity and $p_T$ coverage with good particle identification of the BRAHMS spectrometers allow us to measure the rapidity dependence of the volume, which is proportional to $1/B_2$, and the phase space density of the (anti)-proton source for central Au+Au collisions. We find that $B_2(p_T)$ is almost independent of rapidity and beam energy. Interpreting $1/B_2$ as a volume gives numbers that are very close to HBT data and a size which steadily drops with $p_T$. We find that $B_2(p_T)$ is the same for protons and antiprotons. The phase space density has a weak rapidity dependence but varies rapidily with energy. These results in conjunction with other forward rapidity data start to give us a picture of the longitudinal evolution of the source at RHIC energies. Supported by NSF CAREER award 0449913 [Preview Abstract] |
Saturday, May 2, 2009 12:09PM - 12:21PM |
B10.00006: High $p_T$ jet correlations as a probe of the QGP Andrew Adare Angular correlations involving high-$p_T$ particles associated with partonic jet fragmentation provide an important opportunity to study the hot nuclear matter produced in A+A collisions, particularly when compared against a p+p reference. Recent di-jet correlations results suggest that observables characterizing jet shapes in Au+Au and p+p approach comparable values at high $p_T$, leading to questions about experimental accessibility to quenched partons and the nature of medium-induced energy loss. The latest high-$p_T$ di-jet correlations results from the PHENIX experiment will be presented, as well as a discussion of their interpretation. [Preview Abstract] |
Saturday, May 2, 2009 12:21PM - 12:33PM |
B10.00007: Hadron Ratios in dA Collisions at RHIC and LHC Energies Adeola Adeluyi, George Fai The ratios of particle production in nucleus-nucleus collisions are important indicators of the underlying collision dynamics. In symmetric heavy nucleus-nucleus collisions (e.g. Au$+$Au and Pb$+$Pb), effects like jet energy loss are important and add to the complexity of the interaction. Asymmetric light-heavy collisions (e.g. d$+$Au or d$+$Pb) on the other hand are ``cleaner'' and more suitable for establishing a baseline. In this study, we investigate the role of fragmentation functions in particle ratios at RHIC (d$+$Au) and LHC (d$+$Pb) energies, as a test of our current understanding of the parton fragmentation process. Using the framework of a QCD-improved parton model, we calculate charged and sum of charged hadron ratios at both mid and forward rapidities to evaluate the performance of current fragmentation functions. We compare our results with available experimental data. [Preview Abstract] |
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