Isolated photon production in the color dipole picture

Abstract

A phenomenological study of the isolated photon production in high energy $pp$ and $pA$ collisions at RHIC and LHC energies is performed. Using the color dipole formalism, we investigate the impact of the saturation effects on the production cross sections considering three different phenomenological models for the universal dipole cross section. Predictions for the rapidity dependence of the ratio of $pA$ to $pp$ cross sections are also presented. Moreover, we present our predictions for the correlation function in azimuthal angle $\Delta\phi$ between the photon and a forward pion for different energies and photon rapidities. Our results demonstrate that the presence of saturation effects implies a double-peak structure in the correlation function around $\Delta\phi\simeq\pi$ when the isolated photon and the pion are produced at forward rapidities.