γZcorrections to forward-angle parity-violatingepscattering

Abstract

We use dispersion relations to evaluate the $\ensuremath{\gamma}Z$ box contribution to parity-violating electron scattering in the forward limit arising from the axial-vector coupling at the electron vertex. The calculation makes full use of the critical constraints from recent JLab data on electroproduction in the resonance region as well as high-energy data from HERA. At the kinematics of the ${Q}_{\mathrm{weak}}$ experiment, this gives a correction of ${0.0047}_{\ensuremath{-}0.0004}^{+0.0011}$ to the standard model value 0.0713(8) of the proton weak charge. While the magnitude of the correction is highly significant, the uncertainty is within the anticipated experimental uncertainty of $\ifmmode\pm\else\textpm\fi{}0.003$.