Two-Photon Exchange in (Semi-)Inclusive DIS

TL;DR

This paper investigates the impact of two-photon exchange processes on inclusive and semi-inclusive deep inelastic scattering, revealing new asymmetries and effects relevant for understanding spin phenomena in high-energy physics.

Contribution

It extends the analysis of two-photon exchange effects to SIDIS, identifying a new leading twist $ ext{sin}(2 ext{phi})$ asymmetry and discussing suppression of certain TPE effects.

Findings

Transverse single spin asymmetries arise from TPE in inclusive DIS.

A new leading twist $ ext{sin}(2 ext{phi})$ asymmetry is identified in SIDIS.

TPE effects on Sivers and Collins asymmetries are power-suppressed.

Abstract

In this note we consider effects of a Two-Photon Exchange (TPE) in inclusive DIS and semi-inclusive DIS (SIDIS). In particular, transverse single spin asymmetries are generated in inclusive DIS if more than one photon is exchanged between the lepton and the hadron. We briefly summarize the TPE in DIS in the parton model and extend our approach to SIDIS, where a new leading twist $\sin(2\phi)$ contribution to the longitudinal beam spin asymmetry shows up. Possible TPE effects for the Sivers and the Collins asymmetries in SIDIS are power-suppressed.