Model for Resonance Enhancement of P- and T-noninvariant Effects in Neutron Reactions

Abstract

We consider a simplified model for resonant neutron-nucleus interaction with coupled channels. An analytical solution is given for two coupled channels and arbitrary neutron orbital momentum. A case of a week channel coupling, corresponding to narrow Breit-Wigner resonance, is analyzed in details. As far as the total width of a resonance coincides with the neutron width, the model is directly appropriate only for light nuclei. We study a mixing of two narrow s- and p-wave resonances by P- and P-,T-noninvariant potentials in the first order of perturbation theory. As an example a close-lying pair of s- and p-wave resonances of the $^{35}$Cl nucleus is considered. The favorable possibilities are shown to exist on thick targets for measurements beyond the resonance widths. In particular, an interference minimum near s-wave resonance is of interest for P-odd neutron spin rotation on light spinless nuclei.