| We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The kinematic point [⟨theta lab⟩ = 0.48(GeV/c) 2] is chosen to provide sensitivity, at a level that is of theoretical interest, to the strange electric form factor GsE. The result, A = -14.5 +/- 2.2 ppm, is consistent with the electroweak standard model and no additional contributions from strange quarks. In particular, the measurement implies GsE + 0.39 GsM = 0.023 +/- 0.034(stat) +/- 0.026( dGnE ), where the last uncertainty arises from the estimated uncertainty in the neutron electric form factor. |
