  Background: Proton-nucleus collisions have been used as a intermediate
baseline for the determination of cold medium effects. They lie between
proton-proton collisions in vacuum and nucleus-nucleus collisions which are
expected to be dominated by hot matter effects. Modifications of the quark
densities in nuclei relative to those of the proton are well established
although those of the gluons in the nucleus are not well understood. We focus
on the effect of these on quarkonium production in proton-lead collisions at
the LHC at a center of mass energy of 5.02 TeV.
