Two-photon Exchange Corrections to Single Spin Asymmetry of Neutron and $^3$He

TL;DR

This paper estimates two-photon exchange effects on single spin asymmetries for nucleons and helium-3, finding small effects for nucleons but significant, momentum-dependent effects for helium-3, highlighting the importance of these corrections.

Contribution

It provides the first simple hadronic model calculation of two-photon exchange contributions to single spin asymmetries for nucleons and helium-3.

Findings

Elastic two-photon exchange contributions are small for nucleons.

Two-photon effects are large and angular-dependent for helium-3.

Helium-3 asymmetries are highly sensitive to momentum transfer.

Abstract

In a simple hadronic model, the two-photon exchange contributions to the single spin asymmetries for the nucleon and the $^3$He are estimated. The results show that the elastic contributions of two-photon exchange to the the single spin asymmetries for the nucleon are rather small while those for the $^3$He are relatively large. Besides the strong angular dependence, the two-photon contributions to the single spin asymmetry for the $^3$He are very sensitive to the momentum transfer.