Angular Distribution of Prompt Gamma-rays for the Study of the Breaking of Discrete Symmetries in Compound Neutron Resonance

The weak interaction contained in the nuclear interaction can be observed as the P-violating asymmetry of the neutron capture cross section. The discovery of large enhancement of the P-violating asymmetry in p-wave compound resonances led to a systematic survey in 1990's. The largest enhancement is almost 10$^{\mathrm{6}}$ compared with the nucleon-nucleon P-violating effect and the enhancement is explained as the interference between incident s- and p-wave amplitude. The mechanism of the P-violation has been proposed theoretically to be applicable to enhance the experimental sensitivity to breaking of the symmetry under the time-reversal operation. The enhancement of T-violation is given as $\Delta \sigma_{\mathrm{cp}}=\kappa $(j) ($\omega $/$\upsilon )$ $\Delta \sigma_{\mathrm{p}}$ where $\Delta \sigma_{\mathrm{cp}}$ and $\Delta \sigma _{\mathrm{p}}$ are the CP- and P-violation cross section, $\upsilon $ and $\omega $ are the weak and CP-violating interaction matrix elements between compound resonances with opposite parities, and $\kappa $(j) is the ratio of the spin dependent factor of CP- and P-violation. The determination of $\kappa $(j) is necessary to estimate the experimental sensitivity to T-violation. Therefore we measured the gamma ray angular distribution of radiative decay from compound resonances and evaluated the $\kappa $(j).