The production yields of ϒ(1S), ϒ(2S), and ϒ(3S) quarkonium states are measured through their decays
into muon pairs in the CMS detector, in PbPb and pp collisions at the centre-of-mass energy per nucleon
pair of 2.76 TeV. The data correspond to integrated luminosities of 166 μb−1 and 5.4 pb−1 for PbPb and
pp collisions, respectively. Differential production cross sections are reported as functions of ϒ rapidity
y up to 2.4, and transverse momentum pT up to 20 GeV/c. A strong centrality-dependent suppression is
observed in PbPb relative to pp collisions, by factors of up to ≈2 and 8, for the ϒ(1S) and ϒ(2S) states,
respectively. No significant dependence of this suppression is observed as a function of y or pT. The ϒ(3S)
state is not observed in PbPb collisions, which corresponds to a suppression for the centrality-integrated
data by at least a factor of ≈7 at a 95% confidence level. The observed suppression is in agreement with
theoretical scenarios modeling the sequential melting of quarkonium states in a quark gluon plasma.
CMS Collaboration. "Suppression of ϒ(1S), ϒ(2S), and ϒ(3S) quarkonium states in PbPb collisions at √ sNN = 2.76 TeV”, Physics Letters B. (2017) 770: 357-379. https://doi.org/10.1016/j.physletb.2017.04.031
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