Gluonic Pole Matrix Elements and Universality

TL;DR

This paper examines the spectral properties of quark-quark-gluon correlators and finds that gluonic pole matrix elements vanish for fragmentation functions in many models, impacting the understanding of their universality.

Contribution

It demonstrates that gluonic pole matrix elements for fragmentation functions are zero in a broad class of spectator models, suggesting universality properties.

Findings

Gluonic pole matrix elements vanish for fragmentation functions in many models.

Implication for the universality of fragmentation functions.

Spectral analysis links to the behavior of correlators.

Abstract

We investigate the spectral properties of quark-quark-gluon correlators and use this to study gluonic pole matrix elements. Such matrix elements appear in principle both for distribution functions such as the Sivers function and fragmentation functions such as the Collins function. We find that for a large class of spectator models, the contribution of the gluonic pole matrix element for fragmentation functions vanishes. This result is important in the study of universality for fragmentation functions.