Gluon Shadowing in Heavy-Flavor Production at the LHC.

We study the relevance of experimental data on heavy-flavor [D^{0}, J/ψ, B→J/ψ and ϒ(1S) mesons] production in proton-lead collisions at the LHC to improve our knowledge of the gluon-momentum distribution inside heavy nuclei. We observe that the nuclear effects encoded in both most recent global fits of nuclear parton densities at next-to-leading order (nCTEQ15 and EPPS16) provide a good overall description of the LHC data. We interpret this as a hint that these are the dominant ones.

Production of J / ψ + η(c) versus J / ψ + J / ψ at the LHC: importance of real α(s)(5) corrections.

We proceed for the first time to the evaluation of the Born cross section for J / ψ + η(c) production, namely, via g + g → J/ψ+ η(c) + g, and show that it has a harder P(T) spectrum than the J/ψ-pair yield at the Born level. If one stuck to a comparison at the Born level, one would conclude that J / ψ + η(c) production would surpass that of J / ψ + J / ψ at large P(T). This is nonetheless not the case since J / ψ-pair production, as for single J / ψ, receives leading-P(T) contributions at higher orders in α(s).