Parity-Violating Inelastic Electron-Proton Scattering at Low $Q^2$ Above the Resonance Region

TL;DR

This study measures parity-violating asymmetry in inelastic electron-proton scattering at low $Q^2$ above the resonance region, validating theoretical models of $ ext{γZ}$ interference structure functions relevant for precision electroweak tests.

Contribution

It provides the first experimental measurement of parity-violating asymmetry in this specific inelastic scattering regime, supporting the accuracy of theoretical models used in electroweak physics.

Findings

Measured asymmetry $A_{Inel} = -13.5 ext{ ppm}$ with uncertainties.

Results agree with theoretical calculations of $ ext{γZ}$ interference.

Observed positive asymmetry in inclusive $ ext{π}^-$ production.

Abstract

We report the measurement of the parity-violating asymmetry for the inelastic scattering of electrons from the proton, at $Q^2 = 0.082$ GeV$^2$ and $ W = 2.23$ GeV, above the resonance region. The result $A_{\rm Inel} = - 13.5 \pm 2.0 ({\rm stat}) \pm 3.9 ({\rm syst})$~ppm agrees with theoretical calculations, and helps to validate the modeling of the $\gamma Z$ interference structure functions $F_1^{\gamma Z}$ and $F_2^{\gamma Z}$ used in those calculations, which are also used for determination of the two-boson exchange box diagram ($\Box_{\gamma Z}$) contribution to parity-violating elastic scattering measurements. A positive parity-violating asymmetry for inclusive $\pi^-$ production was observed, as well as positive beam-normal single-spin asymmetry for scattered electrons and a negative beam-normal single-spin asymmetry for inclusive $\pi^-$ production.