Gluon Saturation Effects at the Nuclear Surface: Inelastic Cross Section of Proton-Nucleus at Ultra High Energy Cosmic Ray domain

TL;DR

This paper investigates how gluon saturation at the nuclear surface influences the proton-nucleus inelastic cross section at ultra-high energies, suggesting a faster increase than traditional models and discussing implications for cosmic ray data.

Contribution

It introduces a simplified dipole model to account for gluon saturation effects on the proton-nucleus cross section at ultra-high energies.

Findings

Total cross section increases more rapidly with energy due to gluon saturation.

Gluon saturation effects become significant at ultra-high energies.

Implications for interpreting ultra-high-energy cosmic ray experiments.

Abstract

Considering the high-energy limit of the QCD gluon distribution inside a nucleus, we calculate the proton-nucleus total inelastic cross section using a simplified dipole model. We show that, if gluon saturation occurs in the nuclear surface region, the total cross section of proton-nucleus collisions increases more rapidly as a function of the incident energy compared to that of a Glauber-type estimate. We discuss the implications of this with respect to recent ultra-high-energy cosmic ray experiments.