Gluonic Pole Matrix Elements in Spectator Models

TL;DR

This paper examines gluonic pole matrix elements within spectator models, revealing they are non-zero for distribution functions but vanish for fragmentation functions, impacting the understanding of universality in fragmentation.

Contribution

It provides a spectral analysis showing the contrasting behavior of gluonic pole matrix elements in distribution versus fragmentation functions in spectator models.

Findings

Gluonic pole matrix elements are non-zero in distribution functions.

Gluonic pole matrix elements vanish in fragmentation functions.

Implications for universality of fragmentation functions.

Abstract

We investigate the gluonic pole matrix element contributing to the first $p_T$ moment of the distribution and fragmentation functions in a spectator model. By performing a spectral analysis, we find that for a large class of spectator models, the contribution of gluonic pole matrix elements is non-zero for the distribution correlators, whereas in fragmentation correlators they vanish. This outcome is important in the study of universality for fragmentation functions.