Measurement of effective analyzing powers for the NTOF polarimeter at LAMPF and DLL(0 degree) for Gamow-Teller transitions in p-shell nuclei

Measurements of neutron polarization from (rvec p,rvec n) reactions can provide valuable clues toward understanding the isovector nucleon-nucleus interaction. A neutron time-of-flight polarimeter has been constructed at the Los Alamos Meson Physics Facility to perform such measurements, but before the polarimeter can be used, its effective analyzing powers must be determined. This is accomplished by using the 14C(rvec p,rvec n)14N reaction at a bombarding energy of 494 MeV to produce a beam of neutrons with known polarization, illuminating the detector with these neutrons, and measuring the azimuthal asymmetries after scattering from a hydrogenous analyzer fluid within the detector. Secondary measurements are made using the 2H(rvec p,rvec n)2p reaction with bombarding energies of 318 and 494 MeV to produce a polarized neutron beam. The results from (rvec np) analyzing reactions within the detector agree with values anticipated from free nucleon-nucleon analyzing powers, but the results from (rvec np) analyzing reactions display a more than 33% reduction from the anticipated values. Additionally, measurements are made of the polarization transfer coefficient DLL(0 degree) for rvec p,rvec n Gamow-Teller reactions on 2H, 7Li12C, and 14C targets. For a purely central interaction, one would expect that DLL(0 degree) ∼ -1/3 in the plane wave limit, but a simple average of the Jπ = 0+ → 1+ results at a bombardment energy of 494 MeV gives DLL(0 degree) = -0.689 ± 0.044. Thus, the measurements indicate that the nucleon-nucleus interaction -- which is largely central at 200 MeV -- has strong tensor contributions at higher energy