Collins Asymmetry at Hadron Colliders

TL;DR

This paper demonstrates that the Collins effect in hadron production within jets at high-energy proton-proton collisions exhibits universality, matching results from other processes, due to fundamental gauge invariance principles.

Contribution

It provides a theoretical proof of the universality of the Collins function in hadron colliders based on gauge invariance and Ward identities.

Findings

Collins function is consistent across different scattering processes.

Eikonal propagators do not contribute to the Collins asymmetry phase.

Universality depends on gluon momentum flow and kinematic constraints.

Abstract

We study the Collins effect in the azimuthal asymmetric distribution of hadrons inside a high energy jet in the single transverse polarized proton proton scattering. From the detailed analysis of one-gluon and two-gluon exchange diagrams contributions, the Collins function is found the same as that in the semi-inclusive deep inelastic scattering and e^+e^- annihilations. The eikonal propagators in these diagrams do not contribute to the phase needed for the Collins-type single spin asymmetry, and the universality is derived as a result of the Ward identity. We argue that this conclusion depends on the momentum flow of the exchanged gluon and the kinematic constraints in the fragmentation process, and is generic and model-independent.