Final state interactions and the Sivers function

TL;DR

This paper investigates the impact of non-perturbative final state interactions, including color effects, on the Sivers function in deep inelastic scattering, using eikonal methods to incorporate higher-order gluonic contributions.

Contribution

It introduces a non-perturbative approach to include higher-order gluonic effects in the gauge link, analyzing color effects on the Sivers function beyond one-gluon exchange approximations.

Findings

Confirmed large Nc scaling of Sivers functions

Identified deviations from large Nc behavior at finite Nc

Performed quantitative tests of relations between T-odd TMDs and GPDs

Abstract

The non-vanishing of naive T-odd parton distributions function can be explained by the existence of the gauge link which emerges from the factorized description of the deep inelastic scattering cross section into perturbatively calculable and non-perturbative factors. This path ordered exponential describes initial / final-state interactions of the active parton due to soft gluon exchanges with the target remnants. Although these interactions are non-perturbative, studies of final state interactions have been approximated by perturbative one-gluon exchange in Abelian models. We include higher-order gluonic contributions from the gauge link by applying non-perturbative eikonal methods, incorporating color degrees of freedom in a calculation of the Sivers function. In this context we study the effects of color by considering the FSIs with Abelian and non-Abelian gluon interactions. We confirm the large $N_c$ QCD scaling behavior of Sivers functions and further uncover the deviations for finite $N_c$. Within this framework of FSIs we perform a quantitative check of approximate relations between T-odd TMDs and GPD which goes beyond the discussion of overall signs.