Suppression of excited $Υ$ states relative to the ground state in PbPb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV

Abstract

The relative yields of $Υ$ mesons produced in pp and PbPb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV and reconstructed via the dimuon decay channel are measured using data collected by the CMS experiment. Double ratios are formed by comparing the yields of the excited states, $Υ$(2S) and $Υ$(3S), to the ground state, $Υ$(1S), in both PbPb and pp collisions at the same center-of-mass energy. The double ratios, [$Υ$(nS)/$Υ$(1S)]$_\mathrm{PbPb}$ / [$Υ$(nS)/$Υ$(1S)]$_\mathrm{pp}$, are measured to be 0.308 $\pm$ 0.055 (stat) $\pm$ 0.019 (syst) for the $Υ$(2S) and less than 0.26 at 95% confidence level for the $Υ$(3S). No significant $Υ$(3S) signal is found in the PbPb data. The double ratios are studied as a function of collision centrality, as well as dimuon transverse momentum and rapidity. No significant dependencies are observed.