Two complementary techniques have been proposed and approved at Jefferson Lab to measure the neutron electric form factor G^n_E by bombarding a deuterium target with a longitudinally polarized electron beam. One technique measures the scattering asymmetry from a polarized ^15ND_3 target; the other technique uses an unpolarized liquid deuterium target and a neutron polarimeter to measure the scattering asymmetry. In both techniques, the data--acquisition time to achieve a specified statistical uncertainty will be a minimum when a kinematic figure--of--merit is a maximum. The minimum time occurs for large electron scattering angles. Even though the cross section increases with decreasing scattering angle, a maximum at large angles in the polarization--transfer coefficient or the beam--target asymmetry causes the kinematic figure--of--merit to maximize at large scattering angles.

maintained by Publications Manager