gamma-Z corrections to forward-angle parity-violating e-p scattering

TL;DR

This paper calculates the gamma-Z box correction to parity-violating electron-proton scattering using dispersion relations, incorporating recent experimental data, and finds a significant correction with manageable uncertainty relevant for precision tests of the Standard Model.

Contribution

It provides a detailed dispersion relation calculation of gamma-Z corrections using recent experimental data, improving the precision of the proton weak charge measurement.

Findings

Correction of 0.0047 with uncertainties for the proton weak charge

Uncertainty within the experimental error margin of ±0.003

Significant impact on precision tests of the Standard Model

Abstract

We use dispersion relations to evaluate the 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 Qweak experiment, this gives a correction of 0.0047{+0.0011}{-0.0004}$ 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 +- 0.003.