Parity-Violating Electroweak Asymmetry in (E)Over-Right-Arrowp Scattering
Copyright 2006 American Physical Society. Available on publisher's site at http://dx.doi.org/10.1103/PhysRevLett.96.022003.
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from He-4 at an average scattering angle =5.7 degrees and a four-momentum transfer Q(2)=0.091 GeV2. From these data, for the first time, the strange electric form factor of the nucleon G(E)(s) can be isolated. The measured asymmetry of A(PV)=(6.72 +/- 0.84((stat))+/- 0.21((syst)))x10(-6) yields a value of G(E)(s)=-0.038 +/- 0.042((stat))+/- 0.010((syst)), consistent with zero.