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Suppression of Upsilon Production in d+Au and Au+Au Collisions at sqrt(s_NN) = 200 GeV

Abstract : We report measurements of Upsilon meson production in p+p, d+Au, and Au+Au collisions using the STAR detector at RHIC. We compare the Upsilon yield to the measured cross section in p+p collisions in order to quantify any modifications of the yield in cold nuclear matter using d+Au data and in hot nuclear matter using Au+Au data separated into three centrality classes. Our p+p measurement is based on three times the statistics of our previous result. We obtain a nuclear modification factor for Upsilon(1S+2S+3S) in the rapidity range |y|<1 in d+Au collisions of R_dAu = 0.67 +/- 0.12 (stat.) +/- 0.04 (sys.) +/- 0.08 (pp sys.). A comparison with models including shadowing and initial state parton energy loss indicates the presence of additional cold-nuclear matter suppression. Similarly, in the top 10% most-central Au+Au collisions, we measure a nuclear modification factor of R_AA=0.36 +/- 0.09 (stat.) +/- 0.01 (sys.) +/- 0.04 (pp sys.), which is a larger suppression factor than that seen in cold nuclear matter. Our results are consistent with complete suppression of excited-state Upsilon mesons in Au+Au collisions. The additional suppression in Au+Au is consistent with the level expected in model calculations that include the presence of a hot, deconfined Quark-Gluon Plasma. However, understanding the suppression seen in d+Au is still needed before any definitive statements about the nature of the suppression in Au+Au can be made.
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http://hal.in2p3.fr/in2p3-00919581
Contributor : Sylvie Flores <>
Submitted on : Tuesday, December 17, 2013 - 8:56:26 AM
Last modification on : Thursday, February 7, 2019 - 3:20:04 PM

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L. Adamczyk, W. Borowski, S. Kabana. Suppression of Upsilon Production in d+Au and Au+Au Collisions at sqrt(s_NN) = 200 GeV. Physics Letters B, Elsevier, 2014, 735, pp.127-137. ⟨10.1016/j.physletb.2014.06.028⟩. ⟨in2p3-00919581⟩

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