Quasielastic Scattering of Polarized Electrons from PolarizedHe3and Measurement of the Neutron's Form Factors

We report measurements of asymmetries in quasielastic scattering of polarized electrons from polarized ${\mathrm{He}}^3$ at ${\mathrm{Q}}^2$=-0.2 GeV/c${)}^2$. We measure ${\mathrm{A}}_{\mathrm{T}\prime }$=(-2.6±0.9±0.46)% and ${\mathrm{A}}_{\mathrm{TL}\prime }$=(+1.75±1.2±0.31)%. The asymmetry ${\mathrm{A}}_{\mathrm{T}\prime }$ depends predominantly on the previously measured neutron magnetic form factor and provides a test of theories of spin-dependent quasielastic scattering. Our result for ${\mathrm{A}}_{\mathrm{T}\prime }$ is consistent with a previously reported measurement and suggests that the current theoretical picture is incomplete and final-state-interaction and meson-exchange corrections are necessary if the electric form factor of the neutron is to be reliably extracted from the asymmetry of ${\mathrm{A}}_{\mathrm{TL}\prime }$.