3,029 research outputs found

    Strangeness Production in Heavy-Ion Collisions at STAR

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    We report an overview of strangeness production in Cu+Cu and Au+Au collisions at the energies sNN=\sqrt{s_{NN}} = 62.4 and 200 GeV. We show new mid-rapidly dN/dydN/dy results for the KS0K^{0}_{S}, Λ\Lambda, Ξ\Xi, Ω\Omega particles in Cu+Cu \sNN{62} collisions and compare to results in Au+Au \sNN{62} collisions. We show new results for mid-pTp_T Λ/KS0\Lambda/K^{0}_{S} ratios in Cu+Cu \sNN{62} collisions and again compare to ratios in Au+Au \sNN{62} collisions. Finally, we show the high-pTp_{T} (6.2\sim 6.2 GeV/c) RAA(KS0)R_{AA}(K^{0}_{S}) as a function of system size in Au+Au \sNN{200} collisions and compare to RAA(π)R_{AA}(\pi).Comment: 4 pages, 3 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

    Bulk Properties in Au+Au Collisions at sNN\sqrt{s_{NN}} = 9.2 GeV in STAR Experiment at RHIC

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    One of the primary goals of high-energy heavy-ion collisions is to establish the QCD phase diagram and search for possible phase boundaries. The planned RHIC energy scan program will explore this exciting physics topic using heavy-ion collisions at various center of mass energies. The first test run with Au+Au collisions at sNN\sqrt{s_{NN}} = 9.2 GeV took place in early 2008. We present the results on identified particle ratios, azimuthal anisotropy parameters (v1 and v2) and HBT at midrapidity using data from this run. These results are compared to data for both lower and higher center of mass energies at the AGS, SPS and RHIC. These new data demonstrate the capabilities of the STAR detector for exploring the QCD phase diagram.Comment: 4 pages, 2 figures: Re-submitted to appear in proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

    Strangeness with ALICE: from pp to Pb-Pb

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    We present the measurements of strange and multi-strange hadrons in high energy pp and Pb-Pb collisions at the Large Hadron Collider (LHC) at CERN. The data for these measurements were collected by the ALICE detector in 2010 and 2011. By comparing strangeness data where Quark-Gluon Plasma (QGP) is not expected to be produced (pp collisions) with data where the energy-density of the collision is sufficient to produce the QGP (central and mid-central Pb-Pb collisions), we are able to investigate the properties of the QGP. We characterize the matter created in the collision by presenting strange and multi-strange particle spectra, yields, and transverse momenta in the context of increasing strangeness number, varying collision energy, and the number of nucleons participating in the collision (Npart).Comment: This is a proceedings for the Physics of the LHC 2012 Conference, held in Vancouver, B

    Charmonia production in ALICE

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    Quarkonia states are expected to provide essential information on the properties of the high-density strongly-interacting system formed in the early stages of high-energy heavy-ion collisions. ALICE is the LHC experiment dedicated to the study of nucleus-nucleus collisions and can study charmonia at forward rapidity (2.5 < y < 4) via the mu+ mu- decay channel and at mid rapidity (|y| < 0.9) via the e+ e- decay channel. In both cases charmonia are measured down to zero transverse momentum. The inclusive J/psi production as a function of transverse momentum and rapidity in pp collisions at sqrt{s} = 2.76 and 7 TeV are presented. For pp collisions at sqrt{s} = 7 TeV, the inclusive J/psi production as a function of the charged particle multiplicity, the inclusive J/psi polarization at forward rapidity and the J/psi prompt to non-prompt fraction are discussed. Finally, the analysis of the inclusive J/psi production in the Pb-Pb data collected fall 2011 at a center of mass energy of sqrt{s_{NN}} = 2.76 TeV is presented. Results on the nuclear modification factor are then shown as a function of centrality, transverse momentum and rapidity and compared to model predictions. First results on inclusive J/psi elliptic flow are given.Comment: Proceedings of plenary talk at the 5th international conference on hard and electromagnetic probes of high-energy nuclear collisions (Hard Probes 2012), Cagliari, Italy. 8 pages, 8 figure

    Measurement of electrons from heavy-flavour decays in pp and Pb-Pb collisions with ALICE at the LHC

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    The ALICE experiment has measured at mid-rapidity electrons from heavy-flavour decays in pp collisions at s\sqrt{s} = 2.76 and 7 TeV, and in Pb-Pb collisions at sNN\sqrt{s_{\rm NN}} = 2.76 TeV. In pp collisions, electrons from charm-hadron and from beauty-hadron decays are identified by applying cuts on displaced vertices. The relative yield of electrons from beauty-hadron decays to those from heavy-flavour decays is extracted using electron-hadron correlations. Results are compared to pQCD-based calculations. In Pb-Pb collisions, the pTp_{\rm T} dependence of the nuclear modification factor of electrons from heavy-flavour decays is presented in two centrality classes. The status on the analysis of electrons from beauty-hadron decays is reported in Pb-Pb collisions, in view of the measurement of the corresponding nuclear modification factor.Comment: 4 page, 5 figures, proceedings for the fifth International Conference on Hard and Electromagnetic Probes of High Energy Nuclear Collisions (Hard Probes 2012), May 27 - June 1, Cagliari, Ital

    Non-photonic electron-hadron azimuthal correlation for AuAu, CuCu and pp collisions at sNN=200\sqrt{s_{NN}}=200 GeV

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    We present preliminary STAR results of azimuthal correlations between non-photonic electrons and hadrons in AuAu, CuCu and pp at sNN=200\sqrt{s_{NN}}=200 GeV. Comparison of the e-h correlations from these colliding systems allows one to study the system-size dependence of heavy quark jet-medium interactions. We also report on the relative charm and bottom contributions to non-photonic electrons extracted from correlations measured in pp collisions. Our results, when combined with RAAR_{AA} measurements of non-photonic electrons, constrain the charm and bottom energy loss in the dense medium.Comment: 4 pages 3 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee. v4 has beautified figures for the CuCu and AuAu e-h correlations, no other chang

    Recent Longitudinal Spin Asymmetry Measurements for Inclusive Jet Production at STAR

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    We present measurements of the longitudinal spin asymmetry, ALLA_{LL}, for the inclusive jet signal at STAR. The data presented here are mid-rapidity jets in the transverse momentum range of 5<pT<355<pT<35 GeV/c and come from polarized proton-proton collisions at center of mass energies of s=200\sqrt{s}=200 GeV. We compare our measured ALLA_{LL} values to predictions derived from various parameterizations of the polarized gluon distribution function. The results are shown to provide significant constraints for allowable gluon parameterizations within the measurement's kinematic Bjorken-x range of 0.03<x<0.30.03<x<0.3.Comment: 3 pages, 4 figures, to appear in PANIC 2008 Proceedings, Nuclear Physics A special issu
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