Two-Photon Exchange Corrections to Single Spin Asymmetry of Neutron and 3He

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