Single-spin asymmetries in SIDIS induced by anomalous gluon-quark and photon-quark couplings

TL;DR

This paper investigates how non-perturbative Pauli couplings in quark-photon and quark-gluon interactions influence single-spin asymmetries in SIDIS, revealing significant effects from instanton-induced couplings.

Contribution

It introduces the role of non-perturbative Pauli couplings in generating SSAs in SIDIS within a spectator model framework.

Findings

Non-perturbative couplings cause quark helicity flips.

Rescattering effects lead to SSA azimuthal dependencies.

Instanton model shows strong influence on asymmetries.

Abstract

We calculate the contribution of the non-perturbative Pauli couplings in the quark-photon and quark-gluon vertices to the single-spin asymmetries (SSAs) in semi-inclusive deep inelastic scattering (SIDIS). We describe the nucleon using the spectator model with scalar and axial-vector diquarks. Both of the new couplings can cause the helicity flip of the struck quark. The helicity flip and the rescattering induced by the non-perturbative gluon exchange between the struck quark and diquark lead to the SSAs. Their azimuthal dependencies are the same as that usually ascribed to the Collins and Sivers effects. Our numerical results, based on the instanton model for the QCD vacuum, show that the non-perturbative quark-gluon and quark-photon interactions have a strong influence on these asymmetries.