TMD gluon distributions at small x in the CGC theory

TL;DR

This paper reviews recent theoretical advances in understanding unpolarized TMD gluon distributions at small x within the CGC framework, highlighting their non-universality, equivalence of approaches, and implications for gluon saturation.

Contribution

It clarifies the relationship between TMD factorization and CGC theory, and discusses recent progress in unifying TMD evolution with small-x non-linear evolution.

Findings

Demonstrates the equivalence of TMD and CGC approaches in their overlapping domain

Provides recent results on the behavior of TMD gluon distributions at small x

Discusses advances in unifying TMD evolution with small-x evolution

Abstract

We review recent progress in the description of unpolarized transverse-momentum-dependent (TMD) gluon distributions at small $x$ in the color glass condensate (CGC) effective theory. We discuss the origin of the non-universality of TMD gluon distributions in the TMD factorization framework and in the CGC theory and the equivalence of the two approaches in their overlapping domain of validity. We show some applications of this equivalence, including recent results on the behavior of TMD gluon distributions at small $x$, and on the study of gluon saturation. We discuss recent advances in the unification of the TMD evolution and the non-linear small-$x$ evolution of gluon distributions.