Shadowing Effects on $J/\psi$ and $\Upsilon$ Production at the LHC

Understand

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.