Study of proton structure using heavy meson pair photoproduction*

In this talk, we present our theoretical studies of the inclusive and exclusive photoproduction of heavy quarkonia and open-charm meson pairs, and demonstrate that these channels could be used as novel probes of the hadronic structure. For exclusive production at moderate energies, these channels allow to probe the generalized parton distributions (GPDs) of the proton in the Efremov-Radyushkin-Brodsky-Lepage region. At very high energies, due to onset of saturation effects, the process dynamics are described in the color glass condensate (color dipole) framework, and the suggested channels potentially could be used for detailed studies of the forward dipole scattering amplitude. The inclusive production of the same meson pairs gives access to quadrupole, sextupole, and octupole forward scattering amplitudes. We found that the associated charmonia-bottomonia photoproduction could be used as a potential gateway for the study of the quadrupole scattering amplitude. At present, the suggested channels can be studied in ultraperipheral collisions at LHC, and in the future, it will be possible to study such processes at the Electron Ion Collider (EIC).