Study of ϒ production in pPb collisions at √sNN=8.16 TeV

Abstract

Abstract: The production of Υ(nS) mesons (n = 1, 2, 3) in pPb and Pbp collisions at a centre-of-mass energy per nucleon pair √ sNN = 8.16 TeV is measured by the LHCb experiment, using a data sample corresponding to an integrated luminosity of 31.8 nb−1 . The Υ(nS) mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the differential production cross-sections of the Υ(1S) and Υ(2S) states, their forward-to-backward ratios and nuclear modification factors. The measurements are performed as a function of the transverse momentum pT and rapidity in the nucleon-nucleon centre-of-mass frame y ∗ of the Υ(nS) states, in the kinematic range pT < 25 GeV/c and 1.5 < y∗ < 4.0 (−5.0 < y∗ < −2.5) for pPb (Pbp) collisions. In addition, production cross-sections for Υ(3S) are measured integrated over phase space and the production ratios between all three Υ(nS) states are determined. Suppression for bottomonium in proton-lead collisions is observed, which is particularly visible in the ratios. The results are compared to theoretical models.