Saturation physics at HERA and RHIC : an unified description

Abstract

One of the frontiers of QCD which are intensely investigated in high energy experiments is the high energy (small x) regime, where we expect to observe the non-linear behavior of the theory. In this regime, the growth of the parton distribution should saturate, forming a color glass condensate (CGC). In fact, signals of parton saturation have already been observed both in ep deep inelastic scattering at HERA and in deuteron-gold collisions at RHIC. Currently, a global description of the existing experimental data is possible considering different phenomenological saturation models for the two processes within the CGC formalism. In this Letter we analyze the universality of these dipole cross section parameterizations and verify that they are not able to describe the HERA and RHIC data simultaneously. We analyze possible improvements in the parameterizations and propose a new parameterization for the forward dipole amplitude which allows us to describe quite well the small-x ep HERA data on F2 structure function as well as the dAu RHIC data on charged hadron spectra. It is an important signature of the universality of the saturation physics.