Exclusive heavy vector meson photoproduction in $pp$ and $pPb$ collisions within the GPD approach: A phenomenological analysis

The exclusive $J/\psi$ and $\Upsilon$ photoproduction in proton - proton ($pp$) and proton - lead ($pPb$) collisions at the LHC energies is investigated using the Generalized Parton Distribution (GDP) approach. Assuming the Goloskokov - Kroll (GK) model, we estimate the corresponding total cross - sections and rapidity distributions considering different parametrizations for the unpolarized gluon distribution of the proton. In particular, we compare the linear predictions, associated with DGLAP evolution, with those derived taking into account of the leading nonlinear corrections resulting from gluon recombination. The dependence of our predictions on the choice for the factorization scale is discussed.