Research on Violation of Space-Time Symmetires with Slow Neutrons

研究强子相互作用中破坏宇称的过程有助于获得强子之间弱味道守恒力的信息。研究了几个质量数为-100的核反应中的宇称非守恒效应。用P波共振法测量了晶体的纵向不对称性(A_L)。它被发现与伽马射线能量阈值无关。测定了81&gt；BR；93&gt；Nb；108&gt；Pd；Cd；124&gt；Sn和139&gt；La等靶材的A‘S。得到的非零值分别为：^&lt；139&gt；La(E_n=0.734 eV)、^&lt；81&gt；Br(E_n=0.88 eV)和^&lt；111&gt；Cd(E_n=4.53 eV)的A_L=(9.8±0.3)%、(2.1±0.1)%和-(1.3+0.7-0.4)%。这一结果可以用S入射中子和入射P波中子的两个振幅之间的干涉来解释。还测量了^&lt；139&gt；La的γ&gt；修正项。结果表明，在单次伽马射线跃迁中存在出射通道宇称混合现象。此外，我们还进行了与^&lt；139&gt；La原子核相互作用引起的中子自旋旋转的测量。结果表明，在p波共振区可以观察到宇称破坏效应。对于T破坏实验，必须观察到中子自旋、中子动量和靶核自旋之间的三重关联。我们在LaF_3和LaAl_2O_3晶体中发现了相当大的偏振态。这是T破坏测量的第一步。用激光在室温下对~3He和质子进行了极化实验。这对今后的中子偏振器和偏振分析器都是非常有用的。

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.