We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The kinematic point [⟨θlab⟩=12.3° and ⟨Q2⟩=0.48(GeV/c)2] is chosen to provide sensitivity, at a level that is of theoretical interest, to the strange electric form factor G8 E. The result, A=-14.5±2.2ppm, is consistent with the electroweak standard model and no additional contributions from strange quarks. In particular, the measurement implies G8 E+0.39G8 E=0.023 ± 0.034(stat) ± 0.022(syst) ± 0.026(δGn E), where the last uncertainty arises from the estimated uncertainty in the neutron electric form factor.
ASJC Scopus subject areas
- Physics and Astronomy(all)