Parton saturation scaling function for exclusive production of vector mesons and Deeply Virtual Compton Scattering

Abstract

We provide a universal expression of cross sections for the exclusive vector meson production and Deeply Virtual Compton Scattering (DVCS) in photon-proton and photon-nucleus interactions based on the geometric scaling phenomenon. The theoretical parameterization based on the scaling property depends only on the single variable $\tau_A = Q^2/Q_{\mathrm{sat}}^2$, where the saturation scale, $Q_{\mathrm{sat}}$, drives the energy dependence and the corresponding nuclear effects. This phenomenological result describes all available data from DESY-HERA for $\rho,\,\phi,\,J/\psi$ production and DVCS measurements. A discussion on the size of nuclear shadowing corrections on photon-nucleus interaction is also done.