Proton–nucleus collisions at the LHC: scientific opportunities and requirements

Abstract

Proton-nucleus (p+A) collisions have long been recognized as a crucial
\ncomponent of the physics programme with nuclear beams at high energies,
\nin particular for their reference role to interpret and understand
\nnucleus-nucleus data as well as for their potential to elucidate the partonic
\nstructure of matter at low parton fractional momenta (small-x).
\nHere, we summarize the main motivations that make a proton-nucleus
\nrun a decisive ingredient for a successful heavy-ion programme at the
\nLarge Hadron Collider (LHC) and we present unique scientific opportunities
\narising from these collisions. We also review the status of ongoing
\ndiscussions about operation plans for the p+Amode at the LHC.