title: Two-photon-exchange and gammaZ-exchange corrections to parity-violating elastic electron-proton scattering.
abstract: Leading electroweak corrections play an important role in precision measurements of the strange form factors. We calculate the two-photon-exchange (TPE) and gammaZ-exchange corrections to the parity-violating asymmetry of the elastic electron-proton scattering in a simple hadronic model including the finite size of the proton. We find both can reach a few percent and are comparable in size with the current experimental measurements of strange-quark effects in the proton neutral weak current. The effect of gammaZ exchange is in general larger than that of TPE, especially at low momentum transfer Q2</=1 GeV2. Their combined effects on the values of G(E)s + beta G(M)s [corrected] extracted in recent experiments can be as large as -40% in certain kinematics.
authors.affiliation: Department of Physics, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Hai Qing
authors.initials: HQ
authors.lastname: Zhou
authors.forename: Chung Wen
authors.initials: CW
authors.lastname: Kao
authors.forename: Shin Nan
authors.initials: SN
authors.lastname: Yang