Exclusive vector meson photoproduction at high energies using the discrete BFKL approach

A phenomenological study of the exclusive vector meson photoproduction within the discrete BFKL approach is performed. We estimate the BFKL amplitude in terms of a discrete set of eigenfunctions and use the HERA F-2 data to constrain the free parameters of the model. As a consequence, we derive a parameter free prediction of the energy dependence of the exclusive vector meson cross section. We demonstrate that the HERA and LHCb data for the exclusive J/Psi and Upsilon photoproduction are quite well describe in a large energy range. However, the model overestimates the precise LHCb data for the smallest values of x, which can be interpreted as an indication of the onset of nonlinear (saturation) effects in the QCD dynamics.