Precision Measurements of the Nucleon Strange Form Factors atQ2∼0.1GeV2
We report new measurements of the parity-violating asymmetry A{sub PV} in elastic scattering of 3 GeV electrons off hydrogen and {sup 4}He targets with {theta}{sub lab} {approx} 6.0{sup 0}. The {sup 4}He result is A{sub PV}=(+6.40 {+-} 0.23(stat) {+-} 0.12(syst)) x 10{sup -6}. The hydrogen result is A{sub PV}=(-1.58 {+-} 0.12(stat) {+-} 0.04(syst)) x 10{sup -6}. These results significantly improve constraints on the electric and magnetic strange form factors GE and GM. We extract GE = 0.002 {+-} 0.014 {+-} 0.007 at Q{sup 2} = 0.077 GeV{sup 2}, and GE + 0.09GM = 0.007 {+-} 0.011 {+-} 0.006 at Q{sup 2} = 0.109 GeV{sup 2}, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.