Photoproduction of $J/\psi$ and $Upsilon$ states in exclusive and proton-dissociative diffractive events

The amplitude for p V p, where V is a J/ or ground state or excited vector meson, is calculated in a pQCD k T -factorization approach. We use this amplitude to predict the cross section for exclusive photoproduction of J/, , mesons in proton-proton collisions. Calculations are performed for a variety of unintegrated gluon distributions, and we compare our results to LHCb data. Here we especially focus on the possibilty of constraining saturation effects. Compared to earlier calculations we include both Dirac and Pauli electromagnetic form factors. We discuss the role of the Q Q light-cone wave functions for differential distributions for ratios such as ( )/ (J/). Absorption effects are always taken into account.

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