Study of Υ production and cold nuclear matter effects in pPb collisions at √sNN = 5 TeV

Abstract

Production of Υ mesons in proton-lead collisions at a nucleon-nucleon centre-of-mass energy √sNN = 5 TeV is studied with the LHCb detector. The analysis is based on a data sample corresponding to an integrated luminosity of 1.6 nb−1. The Υ mesons of transverse momenta up to 15 GeV/c are reconstructed in the dimuon decay mode. The rapidity coverage in the centre-of-mass system is 1.5 < y < 4.0 (forward region) and −5.0 < y < −2.5 (backward region). The forward-backward production ratio and the nuclear modification factor for Υ(1S) mesons are determined. The data are compatible with the predictions for a suppression of Υ(1S) production with respect to proton-proton collisions in the forward region, and an enhancement in the backward region. The suppression is found to be smaller than in the case of prompt J/ψ mesons.