Search for a Two-Photon Exchange Contribution in inclusive DIS at sc hermes

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 0.004 < x < 0.9 and 0.1 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 overall asymmetries.