Precision Measurements of the Nucleon Strange Form Factors at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>Q</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:mo>∼</mml:mo><mml:mn>0.1</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mi>GeV</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math>

Abstract

We report new measurements of the parity-violating asymmetry ${A}_{\mathrm{PV}}$ in elastic scattering of 3 GeV electrons off hydrogen and $^{4}\mathrm{He}$ targets with $⟨{\ensuremath{\theta}}_{\mathrm{lab}}⟩\ensuremath{\approx}6.0\ifmmode^\circ\else\textdegree\fi{}$. The $^{4}\mathrm{He}$ result is ${A}_{\mathrm{PV}}=\mathbf{(}+6.40\ifmmode\pm\else\textpm\fi{}0.23(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.12(\mathrm{syst})\mathbf{)}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. The hydrogen result is ${A}_{\mathrm{PV}}=\mathbf{(}\ensuremath{-}1.58\ifmmode\pm\else\textpm\fi{}0.12(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.04(\mathrm{syst})\mathbf{)}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. These results significantly improve constraints on the electric and magnetic strange form factors ${G}_{E}^{s}$ and ${G}_{M}^{s}$. We extract ${G}_{E}^{s}=0.002\ifmmode\pm\else\textpm\fi{}0.014\ifmmode\pm\else\textpm\fi{}0.007$ at $⟨{Q}^{2}⟩=0.077\text{ }\text{ }{\mathrm{GeV}}^{2}$, and ${G}_{E}^{s}+0.09{G}_{M}^{s}=0.007\ifmmode\pm\else\textpm\fi{}0.011\ifmmode\pm\else\textpm\fi{}0.006$ at $⟨{Q}^{2}⟩=0.109\text{ }\text{ }{\mathrm{GeV}}^{2}$, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.