Fragmentation contribution to the transverse single-spin asymmetry in proton-proton collisions

TL;DR

This paper investigates the role of fragmentation in single-spin asymmetries during proton-proton collisions using the collinear twist-3 framework, aiming to clarify the underlying mechanisms and resolve existing sign discrepancies.

Contribution

It provides a detailed calculation of fragmentation contributions involving quark-quark and quark-gluon-quark correlators within the twist-3 approach, advancing understanding of SSAs.

Findings

Fragmentation contributions significantly impact SSAs.

Calculation of quark-quark and quark-gluon-quark correlators.

Potential resolution of the sign mismatch issue.

Abstract

Within the collinear twist-3 framework, we study the single-spin asymmetry (SSA) in collisions between unpolarized protons and transversely polarized protons with focus on the fragmentation term. The fragmentation mechanism must be analyzed in detail in order to unambiguously determine the impact of various contributions to SSAs in hadron production. Such a distinction may also settle the "sign mismatch" between the transverse SSA in proton-proton collisions and the Sivers effect in semi-inclusive deep inelastic scattering. We calculate terms involving quark-quark and quark-gluon-quark correlators, which is an important step in such an investigation.