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In order to test modern theories of two-nucleon bound and scattering states, we have measured the spin polarization of ejectile protons in the electrodisintegration reaction d( e → ,e′ p → )n . Compared with spin-averaged observations, these observables offer the potential of enhanced sensitivity to details of the reaction process. The experiment was carried out in quasielastic kinematics ( q μ q μ =−2m p ω=−0.38 GeV2/c2). Protons were detected at two angles corresponding to neutron recoil momenta pr of 0 and 100 MeV/c. Full nonrelativistic calculations of the polarization transfer components sl and st, including leading order relativistic contributions, describe our measurements well, but calculations of the induced polarization sn at pr=100 MeV/c underpredict the experimental result.

We report a measurement of the neutron detection efficiency for an array of neutron detectors behind a lead-steel wall consisting of 10.16 cm thick lead bricks sandwiched between 3.18 cm steel plates. The neutron detection efficiency e was obtained from the ratio of coincidence to single-arm proton cross sections using the γ + 2 1 H → p + n reaction. Knowledge of the neutron detection efficiency was necessary to extract the cross section for the exclusive 2 H(e,′e n) 1 H reaction, which we used to obtain the elastic magnetic form factor G M n of the neutron. The measurements for three different neutron energies were carried out at the MIT-Bates Linear Accelerator Center with an incident electron beam energy of 254 MeV.

We have built and tested a system that can rapidly reject focal plane polarimeter events whose scattering angle is less than some predetermined minimum value. This produces both a greater system live time and a significant enhancement in the proportion of useful events in the recorded data. The test is based on a pattern recognition scheme employing the LeCroy memory lookup unit. A system decision time of 180 ns has been achieved.