Two-photon exchange in deep inelastic scattering

Abstract We have measured the contribution of the two-photon exchange amplitude in deep inelastic muon-nucleon scattering. We find, with 95% confidence, that the real part of this amplitude is less than 0.017 of the one photon-exchange amplitude. The range of the 4-momentum transfer covered is 0.5 Q 2 c ) 2 .