We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle ⟨θlab⟩=5.7° and a four-momentum transfer Q2=0.091 GeV2. From these data, for the first time, the strange electric form factor of the nucleon GEs can be isolated. The measured asymmetry of APV=(6.72±0.84(stat)±0.21(syst))×10-6 yields a value ofGEs=-0.038±0.042(stat)±0.010(syst), consistent with zero.
Aniol, K. A.; Holmstrom, Timothy; and HAPPEX Collaboration, "Parity-Violating Electron Scattering from (4)He and the Strange Electric Form Factor of the Nucleon" (2006). Chemistry and Physics Faculty Publications. 9.
Phys. Rev. Lett. 96, 022003 (2006)