Parity violation in 232Th neutron resonances above 250 eV
Abstract
The analysis of parity nonconservation PNC measurements performed on 232Th by the TRIPLE Collaboration has been extended to include the neutron energy range of 250 to 1900 eV. Below 250 eV all ten statistically significant parity violations have the same sign. However, at higher energies PNC effects of both signs were observed in the transmission of longitudinally polarized neutrons through a thick thorium target. Although the limited experimental energy resolution precluded analysis in terms of the longitudinal asymmetry, parity violations were observed and the cross section differences for positive and negative neutron helicities were obtained. For comparison, a similar analysis was performed on the data below 250 eV, for which longitudinal asymmetries were obtained previously. For energies below 250 eV, the p-wave neutron strength functions for the J51/2 and J53/2 states were extracted: S1/2 1 5(1.6860.61)31024 and S3/2 1 5(0.7560.18) 31024. The data provide constraints on the properties of local doorway states proposed to explain the PNC sign effect in thorium.