Search for a two-photon exchange contribution to inclusive deep-inelastic scattering

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 .