Title: Hot and cold nuclear matter effects on Υ production at √s = 200 GeV

Abstract: We report on measurements of the dielectron mass spectrum in the Υ region in both d+Au and Au+Au collisions with the STAR detector at RHIC top energy. We compare the Υ yield to the measured cross section from 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. We obtain a nuclear modification factor in d+Au collisions of RdAu = 0.78 ± 0.28(stat) ± 0.20(sys), and in the top 10% most central Au+Au collisions of RAA = 0.34 ± 0.17(stat) ± 0.07(sys). This indicates that the production of Υ mesons in cold nuclear matter is consistent with binary collision scaling, but that in the presence of hot nuclear matter Υ production is suppressed. The measured suppression is compared to models of bottomonium dissociation, which can be used to obtain information as to the temperature reached by the hot quark-gluon plasma.

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