LHCb results in proton-nucleus collisions at the LHC

The forward acceptance of the LHCb detector allows it to probe proton-ion collision in a unique kinematic range, complementary to the other LHC experiments. The production of J/Ψ and ϒ-mesons decaying into two muons is studied at the LHCb experiment in proton-lead collisions at a proton-nucleon centre-of-mass energy = 5 TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 1.6 nb^-1. The nuclear modification factor and the forward-backward production ratio are determined for J/Ψ and ϒ(1S) mesons. Clear suppression of prompt J/Ψ production is observed with respect to the production in pp collisions at large rapidity, while the suppression of J/Ψ from b-hadron decays is less pronounced. The nuclear modification factor for ϒ(1S) mesons in the forward region is found to be similar to those for J/Ψ from b-hadron decays. Furthermore, a first observation of Z bosons in proton-lead collisions is reported. (paper)