Observation of the $\mathrm{{\rm Y}}$(3S) meson and suppression of $\mathrm{{\rm Y}}$ states in PbPb collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 5.02 TeV

The production of $\mathrm{{\rm Y}}$(2S) and $\mathrm{{\rm Y}}$(3S) mesons in lead-lead (PbPb) and proton-proton (pp) collisions is studied in their dimuon decay channel using the CMS detector at the LHC. The $\mathrm{{\rm Y}}$(3S) meson is observed for the first time in PbPb collisions, with a significance above five standard deviations. The ratios of yields measured in PbPb and pp collisions are reported for both the $\mathrm{{\rm Y}}$(2S) and $\mathrm{{\rm Y}}$(3S) mesons, as functions of transverse momentum and PbPb collision centrality. These ratios, when appropriately scaled, are significantly less than unity, indicating a suppression of $\mathrm{{\rm Y}}$ yields in PbPb collisions. This suppression increases from peripheral to central PbPb collisions. Furthermore, the suppression is stronger for $\mathrm{{\rm Y}}$(3S) mesons compared to $\mathrm{{\rm Y}}$(2S) mesons, extending the pattern of sequential suppression of quarkonium states in nuclear collisions previously seen for the $\psi$/J, $\psi$(2S), $\mathrm{{\rm Y}}$(1S), and $\mathrm{{\rm Y}}$(2S) mesons.