Search for a Two-Photon Exchange Contribution to Inclusive Deep-Inelastic Scattering

TL;DR

This study measured single-spin asymmetries in inclusive deep-inelastic scattering to search for two-photon exchange effects, finding results consistent with zero, thus constraining such contributions in the examined kinematic range.

Contribution

It provides the first experimental search for two-photon exchange signals in inclusive deep-inelastic scattering with transversely polarized targets.

Findings

Asymmetries are consistent with zero within uncertainties

Results constrain two-photon exchange contributions

Uncertainties are of order 10^{-3} for integrated asymmetries

Abstract

The transverse-target single-spin asymmetry for inclusive deep-inelastic scattering with effectively unpolarized electron and positron beams off a transversely polarized hydrogen target was measured, with the goal of searching for a two-photon exchange signal in the kinematic range 0.007 < x_B < 0.9 and 0.25 GeV**2 < Q**2 < 20 GeV**2. In two separate regions Q**2 > 1 GeV**2 and Q**2 < 1 GeV**2, and for both electron and positron beams, the asymmetries are found to be consistent with zero within statistical and systematic uncertainties, which are of order 10**(-3) for the asymmetries integrated over x_B.