Measurement of the Neutron Electric Form FactorGenat0.67(GeV/c)2via3He→(e→,e′n)

We have measured the neutron electric form factor ${G}_{\mathrm{en}}$ via ${}^{3}\stackrel{\ensuremath{\rightarrow}}{\mathrm{He}}(\stackrel{\ensuremath{\rightarrow}}{e}{,e}^{\ensuremath{'}}n)\mathrm{pp}$ at ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.67(\mathrm{GeV}/c{)}^{2}$ using the 3-spectrometer facility of the A1 Collaboration at the Mainz Microtron and a dedicated neutron detector. High pressure polarized ${}^{3}\stackrel{\ensuremath{\rightarrow}}{\mathrm{He}}$ gas was used as a target of polarized neutrons. ${G}_{\mathrm{en}}$ is determined from the ratio of the asymmetries ${A}_{\ensuremath{\perp}}{/A}_{\ensuremath{\parallel}}$ measured in quasifree kinematics with the target spin perpendicular and parallel to the momentum transfer. We find ${G}_{\mathrm{en}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.052\ifmmode\pm\else\textpm\fi{}0.011\ifmmode\pm\else\textpm\fi{}0.005$.