$J/\psi$ production in proton-lead collisions at LHCb

The production of prompt J / ψ and J / ψ from b -hadron decays has been studied in proton-lead collisions with the LHCb detector at the proton-nucleon centre-of-mass energy √ s NN = 5 TeV . The nuclear modification factor and forward-backward production ratio for prompt J / ψ are determined for the first time. The results show clear suppression of the J / ψ yield with respect to pp collisions in the forward region. Theoretical predictions are in good agreement with the experiment results. The analysis is based on a data sample corresponding to an integrated luminosity of 1nb − 1 .