Probing nuclear parton densities (and more) from γ + Q production in p–A and A–A collisions

Abstract

We present a detailed phenomenological study of the associated production of a prompt photon and a heavy-quark jet (charm or bottom) in proton-nucleus (p–A) collisions. The dominant contribution to the cross-section comes from the gluon-heavy-quark (gQ) initiated subprocess, making this process very sensitive to the gluon and the heavy quark nuclear parton densities. We show that the future p–A data to be collected at the LHC in this channel should help to disentangle the various nPDF sets currently available. In heavy-ion collisions, the photon transverse momentum can be used to gauge the initial energy of the massive parton propagating through the dense QCD medium produced in those collisions, making γ + Q production a powerful process in order to probe energy loss dynamics in the heavy-quark sector.