Study of $\hat{I}\yen$ production in $p$Pb collisions at $\sqrt{s_{NN}}=8.16$ TeV

Abstract

The production of $\hat{I}\yen (nS)$ mesons ($n=1,2,3$) in $p$Pb and Pb$p$ collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{NN}}=8.16$ TeV is measured by the LHCb experiment, using a data sample corresponding to an integrated luminosity of 31.8 nb${}^{-1}$. The $\hat{I}\yen (nS)$ mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the differential production cross-sections of the $\hat{I}\yen (1S)$ and $\hat{I}\yen (2S)$ states, their forward-to-backward ratios and nuclear modification factors, performed as a function of the transverse momentum \pt and rapidity in the nucleon-nucleon centre-of-mass frame $y^{\ast }$ of the $\hat{I}\yen (nS)$ states, in the kinematic range $p_{\mathrm{T}}<25$ GeV/$c$ and $1.5<y^{\ast }<4.0$ ($-5.0<y^{\ast }<-2.5$) for $p$Pb (Pb$p$) collisions. In addition, production cross-sections for $\hat{I}\yen (3S)$ are measured integrated over phase space and the production ratios between all three $\hat{I}\yen (nS)$ states are determined. The measurements are compared to theoretical predictions and suppressions for quarkonium in $p$Pb collisions are observed.

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2018-035.html updated to correct figure 11 (numerical results unchanged)