Calculation of TMD Evolution for Transverse Single Spin Asymmetry Measurements

TL;DR

This paper calculates the evolution of the Sivers transverse single spin asymmetry using TMD formalism and compares it with experimental data, confirming the suppression effects predicted by TMD evolution.

Contribution

It applies the Collins-Soper-Sterman formalism to TMD evolution of TSSA, utilizing universality and existing experimental inputs to validate theoretical predictions.

Findings

COMPASS measurements align with TMD evolution suppression

TMD evolution describes scale dependence of TSSA

Universality of TMD functions is supported by data

Abstract

The Sivers transverse single spin asymmetry (TSSA) is calculated and compared at different scales using the TMD evolution equations applied to previously existing extractions. We apply the Collins-Soper-Sterman (CSS) formalism, using the version recently developed by Collins. Our calculations rely on the universality properties of TMD-functions that follow from the TMD-factorization theorem. Accordingly, the non-perturbative input is fixed by earlier experimental measurements, including both polarized semi-inclusive deep inelastic scattering (SIDIS) and unpolarized Drell-Yan (DY) scattering. It is shown that recent COMPASS measurements are consistent with the suppression prescribed by TMD evolution.