Perturbative treatment of parity nonconservation in neutron-nucleus scattering within the optical model

The question of parity nonconservation in compound nuclear reactions is treated within the optical model. This model supplies a description of average cross section spin polarization, spin rotation, and the parity nonconservation direct testing quantity, the longitudinal asymmetry. Taking for the optical model potential a sum of a parity conserving strong complex potential and a parity nonconserving (PNC) weak potential, the above physical quantities are then evaluated, with the PNC potential treated with perturbation theory. The compound elastic, absorption, and total components of all the measurable quantities are discussed. Application is then made to the recent TRIPLE data on the n${+}^{232}$Th systems at thermal neutrons energies.