Two-photon cross-sections from the saturation model

Abstract

A saturation model for the total gamma-gamma and gamma*-gamma* cross-sections and for the real photon structure function F_2^gamma(x,Q^2) is described. The model is based on a QCD dipole picture of high energy scattering. The two-dipole cross-section is assumed to satisfy the saturation property with the saturation radius taken from the GBW analysis of the gamma*-p interaction at HERA. The model is combined with the QPM and non-pomeron reggeon contributions an it gives a very good description of the data on the gamma-gamma total cross-section, on the photon structure function F_2^gamma(x,Q^2) at low x and on the gamma*-gamma* cross-section. Production of heavy quarks in gamma-gamma collisions is also studied.