Parity-nonconserving Effects in n?p Capture at Thermal Energies

Abstract

The circular polarization and asymmetry, about the incident neutron spin direction, of the photon released in the reaction n + p -+ d + y at thermal neutron energies are consequences of parity violation in the n-p interaction. A formalism is developed which expresses the polarization and asymmetry in terms of the half-off-shell transition matrix, and calculations are performed for several models of the weak parity-nonconserving N-N interaction. The results indicate that the polarization is sensitive to the choice of both the strong N-N interaction and weak N-N interaction while the asymmetry is sensitive mainly to the latter. The observed polarization is of the same sign and rather larger than that calculated with the conventional weak N-N potential. Difficulties in the present method indicate that this discrepancy cannot be regarded as significant.