Research on Violation of Space-Time Symmetires with Slow Neutrons

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The study of parity-violating processes in hadronic interactions is useful to obtain information on the weak flavor conserving force between hadrons.The parity non-conserving effect was investigated in low energy (n.gamma) reactions for several nuclei with mass number of -100. The longitudinal asymmetries (A_L) were measured in p-wave resonances. It was found to be independent of the gamma-ray energy thresholds. The A 's were measured for the targets of ^<81>Br, ^<93>Nb, ^<108>Pd, ^<111>Cd, ^<124>Sn and ^<139>La. The obtained non-zero values are A_L=(9.8 0.3)%, (2.1 0.1)% and -(1.3+0.7-0.4)% for ^<139>La (E_n=0.734 eV), ^<81>Br(E_n=0.88 eV) and ^<111>Cd(E_n=4.53 eV), respectively. The results can be explained in terms of the interference between two amplitudes of s- and p-wave incident neutrons.The sigma^^*_n.K^^*_<gamma> correction term for ^<139>La has been also measured. The result suggests the existence of exit-channel parity-mixing in a single gamma-ray transitions.In addition, we have carried out a test of the measurement of the neutron spin rotation due to the interaction with the ^<139>La nuclei. It was found that the parity violation effect could be observed in the p-wave resonance region. For T-violation experiments, a triple correlation among the neutron spin, the neutron momentum and the target nuclear spin has to be observed. We have found sizable polarization of ^<139>La in crystals of LaF_3and LaA1O_3. It is the first step of the T-violation measurement.Polarization experiments of the ^3He and the proton in room temperature have been carried out using laser beams. These are quite useful for the polarizer and the polarization analyzer of neutrons in future.