New results from the HAPPEX Experiments at Q2 = 0.1GeV/c2
Abstract.The nucleon's strange electric and magnetic form factors GEs and GMs can be probed via parity-violating electron scattering. The HAPPEX Collaboration has made new measurements of the parity-violating asymmetry APV in elastic scattering of 3GeV electrons off hydrogen and 4He targets with 〈θlab〉 ≈ 6.0° . For 4He the preliminary result is APV = (+ 6.43±0.23(stat)±0.22(syst))×10-6 . For hydrogen the preliminary result is APV = (- 1.60±0.12(stat)±0.05(syst))×10-6 . From these values we extract GsE = 0.004±0.014±0.013 at 〈Q2〉 = 0.077 GeV/c^2 , and GsE +0.09GsM = 0.004±0.011±0.005 at 〈Q2〉 = 0.109 GeV/c^2 , both consistent with zero, providing stringent new limits on the role of strange quarks in the vector structure of the nucleon.