Gluon Saturation and S-Matrix Unitarity

TL;DR

This paper investigates how gluon distributions inside protons behave at low x, demonstrating saturation effects due to S-matrix unitarity, with implications for understanding proton structure.

Contribution

It introduces a loop-loop correlation model that respects impact parameter space unitarity to analyze gluon saturation phenomena.

Findings

Low-x gluon saturation occurs at the impact parameter level.

The integrated gluon distribution does not saturate due to increasing proton size.

S-matrix unitarity constrains gluon distributions at small x.

Abstract

The impact parameter dependent gluon distribution of the proton xG(x,Q^2,b) is investigated in a loop-loop correlation model that respects the S-matrix unitarity condition in impact parameter space. We find low-x saturation of G(x,Q^2,b) as a manifestation of S-matrix unitarity. The integrated gluon distribution xG(x,Q^2) does not saturate because of the growth of the effective proton radius with decreasing x.