On gauge invariance of transverse momentum dependent distributions at small-x

TL;DR

This paper develops a new formulation of small-x TMD operators using transverse gauge links, enabling direct matching with standard gluon TMDs and extending calculations beyond leading twist.

Contribution

It introduces a novel formulation of small-x TMD operators with transverse gauge links, facilitating direct matching and higher-twist computations.

Findings

Formulation of small-x operators in terms of transverse gauge links

Direct matching with standard gluon TMD distributions

Framework for computing TMDs beyond leading twist

Abstract

Transverse momentum dependent (TMD) distributions at small x exhibit a rich infinite twist structure that encompasses the leading twist (partonic) distributions as well as the physics of gluon saturation. Progress to further the connection between the standard TMD framework at moderate x and small x has been recently made. In this context, we show that light cone Wilson line operators at small-x can be formulated in terms of transverse gauge links. This new formulation of small x operators allows a direct matching with the standard leading twist gluon TMD distributions and provides an efficient and general prescription for computing TMD distributions at small x beyond leading twist.