Precision Measurements of the Nucleon Strange Form Factors at Q(2)∼0.1 GeV(2)

K. A. Aniol, California State University - Los Angeles
Timothy Holmstrom, Longwood University
HAPPEX Collaboration

© 2007 The American Physical Society. The original publication is available at http://link.aps.org/doi/10.1103/PhysRevLett.98.032301

Abstract

We report new measurements of the parity-violating asymmetry A_PV in elastic scattering of 3 GeV electrons off hydrogen and ⁴He targets with ⟨θ_lab⟩≈6.0°. The ⁴He result is A_PV=(+6.40±0.23(stat)±0.12(syst))×10^-6. The hydrogen result is A_PV=(-1.58±0.12(stat)±0.04(syst))×10^-6. These results significantly improve constraints on the electric and magnetic strange form factors G_E^s and G_M^s. We extract G_E^s=0.002±0.014±0.007 at ⟨Q²⟩=0.077 GeV², and G_E^s+0.09G_M^s=0.007±0.011±0.006 at ⟨Q²⟩=0.109 GeV², providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.