Photoproduction of J/ψ and ϒ in exclusive and proton dissociative diffractive events

We use a perturbative QCD based k_T -factorization approach, to calculate the amplitude for the diffractive γp → Vp processes, where V is a J/ψ or ϒ ground state or excited vector meson. Using these amplitudes, we evaluate the cross section for exclusive photoproduction of J/ψ, ψ′, ϒ mesons in proton-proton collisions. Calculations are performed for a variety of unintegrated gluon distributions, and we compare our results to LHCb data. Absorption effects are taken into account at the amplitude level. We also discuss the related diffractive production in proton dissociative events. Here we concentrate on electromagnetic dissociation , which is calculable without additional free parameters. Besides being of interest in their own right, dissociative events constitute an important experimental background to exclusive production.