Saturation and Geometrical Scaling: from Deep Inelastic ep Scattering to Heavy Ion Collisions

TL;DR

This paper discusses how gluon saturation and the resulting geometrical scaling phenomenon manifest across various high-energy physics processes, linking deep inelastic scattering and heavy ion collisions.

Contribution

It provides a comprehensive overview of geometrical scaling arising from gluon saturation in QCD across different reactions and energy scales.

Findings

Saturation leads to a universal scale called saturation momentum.

Geometrical scaling is observed in multiple high-energy processes.

Saturation effects dominate at large energies in certain kinematic domains.

Abstract

Saturation of gluon distribution is a consequence of the non-linear evolution equations of QCD. Saturation implies the existence of so called saturation momentum which is defined as a gluon density per unit rapidity per transverse area. At large energies for certain kinematical domains saturation momentum is the only scale for physical processes. As a consequence different observables exhibit geometrical scaling (GS). We discuss a number of examples of GS in different reactions.