Nuclear modification of $\mathrm{{\rm Y}}$ states in pPb collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=$ 5.02 TeV

Production cross sections of $\mathrm{{\rm Y}}$(1S), $\mathrm{{\rm Y}}$(2S), and $\mathrm{{\rm Y}}$(3S) states decaying into ${\mu }^{+}{\mu }^{-}$ in proton-lead (pPb) collisions are reported using data collected by the CMS experiment at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=$ 5.02 TeV. A comparison is made with corresponding cross sections obtained with pp data measured at the same collision energy and scaled by the Pb nucleus mass number. The nuclear modification factor for $\mathrm{{\rm Y}}$(1S) is found to be $R_{\mathrm{p}\mathrm{P}\mathrm{b}}(\mathrm{{\rm Y}}(1S))$ = 0.806 $\pm$ 0.024 (stat) $\pm$ 0.059 (syst). Similar results for the excited states indicate a sequential suppression pattern, such that $R_{\mathrm{p}\mathrm{P}\mathrm{b}}(\mathrm{{\rm Y}}(1S))$ $>$ $R_{\mathrm{p}\mathrm{P}\mathrm{b}}(\mathrm{{\rm Y}}(2S))$ $>$ $R_{\mathrm{p}\mathrm{P}\mathrm{b}}(\mathrm{{\rm Y}}(3S))$. The suppression is much less pronounced in pPb than in PbPb collisions, and independent of transverse momentum $p_{\mathrm{T}}^{\mathrm{{\rm Y}}}$ and center-of-mass rapidity $y_{\mathrm{C}\mathrm{M}}^{\mathrm{{\rm Y}}}$ of the individual $\mathrm{{\rm Y}}$ state in the studied range $p_{\mathrm{T}}^{\mathrm{{\rm Y}}}$ $<$ 30 GeV$\mathrm{/}c$ and $\mathrm{\mid }{y}_{\mathrm{C}\mathrm{M}}^{\mathrm{{\rm Y}}}\mathrm{\mid }$ $<$ 1.93. Models that incorporate sequential suppression of bottomonia in pPb collisions are in better agreement with the data than those which only assume initial-state modifications.