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Volume 345 - International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (HardProbes2018) - Heavy Flavours & Quarkonia
Understanding sequential quarkonium suppression with $\Upsilon(nS)$ measurements in pp, pPb and PbPb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the CMS detector
J. Park* on behalf of the CMS collaboration
*corresponding author
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Pre-published on: 2019 January 14
Published on: 2019 April 24
The production cross sections of the $\Upsilon\textrm{(1S)}$, $\Upsilon\textrm{(2S)}$, and $\Upsilon\textrm{(3S)}$ states were measured separately using the CMS experimental apparatus, in proton-proton (pp) and lead-lead (PbPb) collisions at 5.02 TeV. The final results of the nuclear modification factors, $R_{AA}$, are reported of the three upsilon states as a function of transverse momentum ($p_{T}$), rapidity ($y$) and PbPb collision centrality. The data show a significant suppression of all three states following a sequential ordering, $R_{AA}(\Upsilon\textrm{(1S)}) > R_{AA}(\Upsilon\textrm{(2S)}) > R_{AA}(\Upsilon\textrm{(3S)})$. The suppression of $\Upsilon\textrm{(1S)}$ is larger than that seen at $\sqrt{s_{NN}}$ = 2.76 TeV, though the two are compatible within uncertainties. The $\Upsilon\textrm{(3S)}$ was not observed in PbPb collisions, being suppressed by more than a factor 10 at the 95$\%$ confidence level.
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