The Two-Photon-Exchange and γZ-Exchange Corrections to parity-Violating Elastic Electron-Proton Scattering

Zhou, Hai Qing; Kao, Chung Wen; Yang, Shin Nan

The Two-Photon-Exchange and γZ-Exchange Corrections to parity-Violating Elastic Electron-Proton Scattering

Authors

Zhou, Hai Qing

Kao, Chung Wen

Yang, Shin Nan

Description

Leading electroweak corrections play an important role in precision measurements of the strange form factors. We calculate the two-photon-exchange (TPE) and $γZ$-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 $γZ$-exchange is in general larger than that of TPE, especially at low momentum transfer $Q^2\le 1 GeV^2$. Their combined effects on the values of $G^s_E+βG^s_M$ extracted in recent experiments can be as large as -40% in certain kinematics.
4 pages, 3 Figs