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

The collaboration
JHEP 11 (2018) 194, 2018.

Abstract (data abstract)
CERN-LHC. The production of $\Upsilon(nS)$ 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 $\Upsilon(nS)$ mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the differential production cross-sections of the $\Upsilon(1S)$ and $\Upsilon(2S)$ states, their forward-to-backward ratios and nuclear modification factors, performed as a function of the transverse momentum p_{T} and rapidity in the nucleon-nucleon centre-of-mass frame $y^*$ of the $\Upsilon(nS)$ states, in the kinematic range $p_{T}<25$ GeV$/c$ and $1.5<y^*<4.0$ ($-5.0<y^*<-2.5$) for $p$Pb (Pb$p$) collisions. In addition, production cross-sections for $\Upsilon(3S)$ are measured integrated over phase space and the production ratios between all three $\Upsilon(nS)$ states are determined.