Non-Universality of Transverse Momentum Dependent Parton Distributions at Small-x

TL;DR

This paper investigates whether transverse momentum dependent parton distributions are universal at small-x by comparing different scattering processes, demonstrating non-universality through explicit model calculations and discussing implications for saturation phenomena.

Contribution

It provides the first explicit calculation showing the non-universality of TMD parton distributions at small-x in a specific model, highlighting process dependence.

Findings

Demonstrates non-universality of TMD PDFs at small-x

Performs explicit all-order gauge boson exchange calculations

Discusses implications for di-hadron correlations in dA collisions

Abstract

We study the universality issue of the transverse momentum dependent parton distributions at small-x, by comparing the initial/final state interaction effects in dijet-correlation in pA collisions with those in deep inelastic lepton nucleus scattering. We demonstrate the non-universality by performing an explicit calculation in a particular model where the multiple gauge boson exchange contributions are summed up to all orders. We comment on the implications of our results on the theoretical interpretation of di-hadron correlation in dA collisions in terms of the saturation phenomena in deep inelastic lepton nucleus scattering.