Analyzing power measurements of the n-p final-state interaction in the n-d breakup reaction

Abstract

Recently we have made kinematically incomplete and complete measurements of the vector analyzing powers Ay(8) for the n-p final-state interaction (FSI) in the n-d breakup reaction at 12 MeV. The kinematitally incomplete (KI) experimental arrangement, measuring the momentum of one outgoing neutron and the energy of the proton, permitted us to measure several breakup processes simultaneously to a high statistical aCCUracy and was therefore favored over the kinematically complete (KC) arrangement in which both outgoing neutrons were detected. Consequently, the KC measurements were conducted by parasiting on the KI experiment by adding a pair of neutron detectors at forward angles to detect the Second outgoing neutron. The incentives for performing the measurements are multiple. The investigation of polarization effects in the n-d breakup processes Should provide unique information about various aspects of the nuclear force acting in this three-nucleon system. As is well known, the predictions of Ay(e) for n-d elastic scattering at low energies are strongly Sensitive to the inclusion of the Pand D-wave interactions, while in Contrast, the description of the dlfferentlal cross section ~(8) data displays only slight sensitivity to the Pand D-wave interactions.l, 2 Because of the sensitivities observed in the Ay(8) data for elastic Scattering, it is likely that the Ay(8) data for the breakup processes Wlll exhibit sensitlvlties to aspects of the nuclear force that are SUpPressed in the a(8) data. Also, effects due to the three-nucleon force and charge-symmetry breaking might be revealed in such polarization data. The technique employed in these measurements used the pulsed polar~zed beam facilities at Triangle University Nuclear Laboratory (TUNL). The experimental setup is shown in Fig. I. The polarized neutrons were ~roduced via the 2H(~,~) source reaction, using the neutrons emerging at 0o. The incident deuteron beam was pulsed to enable the use of