Spectral analysis of gluonic pole matrix elements for fragmentation

TL;DR

This paper investigates the spectral properties of gluonic pole matrix elements in fragmentation functions using a spectator model, finding that these contributions vanish in many models, which impacts the understanding of universality in fragmentation functions.

Contribution

It demonstrates that gluonic pole contributions to fragmentation functions vanish in a broad class of spectator models, supporting the universality hypothesis.

Findings

Gluonic pole contributions vanish in many spectator models.

Supports the universality of fragmentation functions.

Confirms previous findings with a different approach.

Abstract

The non-vanishing of gluonic pole matrix elements can explain the appearance of single spin asymmetries in high-energy scattering processes. We use a spectator framework approach to 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 in fragmentation functions vanishes. This outcome is important in the study of universality for fragmentation functions and confirms findings using a different approach.