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Volume 345 - International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (HardProbes2018) - Plenary
Measurements of Bottomonium production in pp and PbPb collisions at sNN = 5.02 TeV
G. Oh
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Pre-published on: 2019 February 13
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Bottomonia are important probes of the quark-gluon plasma since they are produced at early times and propagate through the medium. The production cross sections of the three $\Upsilon$ states (1S, 2S, 3S) were measured by CMS in pp and PbPb collisions at $\sqrt{s_{\mathrm{NN}}\space}$ = 5.02 ${\mathrm{TeV}}\space$. The nuclear modification factors, ${R_\mathrm{AA}}$, derived from the ${\text{PbPb}}$ to pp ratio of yields for each state, are studied as functions of meson rapidity between 0 to 2.4 and transverse momentum ${p_\mathrm{T}}$ spanning from 0 to 30 ${\mathrm{GeV/\it{c}}}$, as well as PbPb collision centrality 0 to 100\%.
A strong suppression of \raa is observed in PbPb collisions but the $\Upsilon$(3S) was not observed clearly in PbPb collisions.
The upper limit on the ${R_\mathrm{AA}}$ of $\Upsilon$(3S) integrated over ${p_\mathrm{T}}$, rapidity and centrality is 0.096 at 95\% confidence level, which is the strongest suppression observed for a quarkonium state in heavy ion collisions to date. The suppression of $\Upsilon$(1S) is larger than that seen at $\sqrt{s_{\mathrm{NN}}\space}$ = 2.76 ${\mathrm{TeV}}$, although the two are still compatible within uncertainties.
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