The Role of Gauge Invariance in Single-Spin Asymmetries

TL;DR

This paper discusses how gauge invariance, via Wilson lines, influences the calculation of single-spin asymmetries in hadronic scattering, showing that it leads to gluonic pole cross sections instead of standard partonic ones.

Contribution

It reveals that gauge invariance modifies the hard functions in spin asymmetries to be gluonic pole cross sections through Wilson lines.

Findings

Hard functions are given by gluonic pole cross sections.

Gauge invariance affects the structure of spin asymmetries.

Wilson lines play a crucial role in this modification.

Abstract

We argue that through the Wilson lines, gauge invariance has as an effect that the hard functions in weighted spin-asymmetries in hadronic scattering processes are given by gluonic pole cross sections, rather than the usual partonic cross sections.