Parity-Violating Electron Deuteron Scattering and the Proton’s Neutral Weak Axial Vector Form Factor

We report on a new measurement of the parity-violating asymmetry in quasielastic electron scattering from the deuteron at backward angles at $Q^2=0.038$ $(\mathrm{GeV}/c{)}^2$. This quantity provides a determination of the neutral weak axial vector form factor of the nucleon, which can potentially receive large electroweak corrections. The measured asymmetry $A=-3.51\pm 0.57(\mathrm{stat})\pm 0.58(\mathrm{syst})\mathrm{ppm}$ is consistent with theoretical predictions. We also report on updated results of the previous experiment at $Q^2=0.091$ $(\mathrm{GeV}/c{)}^2$, which are also consistent with theoretical predictions.