Parity and Time Reversal Test in Slow Neutron Absorption

慢中子吸收中的宇称和时间反转测试

基本信息

批准号：
04044082
负责人：
MASAIKE Akira
金额：
$ 3.71万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

The interaction of epithermal neutrons with nuclei consists of elastic scattering by optical potential of nuclei and resonance absorption. The compound resonances are well resolved each other in the epithermal energy region, whereas the resonances are overlapped in higher energy region for heavy nuclei. Small contribution of p-wave resonances is observed although s-wave contribution is dominant in the case that the resonances are well resolved. Parity violating effect can be accumulated during the life time of compound resonances. The enhancement of parity-violation is explained as the result of the interference between two opposite parity amplitudes, e.g. s- and p-wave amplitudes. The study of parity-violating enhancement mechanism is very important for possible T-violation experiments.P-violating asymmetries with respect to the helicity of incident neutrons were measured by the neutron transmission method in p-wave resonances of uranium, thorium, indium, silver and niobium at LAMPF, Los Alamos as an International Scientific Research Program.At Los Alamos a longitudinal polarized proton filter which consists of NH_3 beads were used to obtain longitudinally polarized neutron beams. ^<10>B loaded liquid scintillator was used in order to detect neutrons at very high counting rate in the energy region of a few hundred eV.A method to measure the capture gamma-rays was also used to detect small p-wave resonances with sufficient accuracy at Los Alamos. Gamma-ray detectors of CsI, BaF_2 and GSO were constructed and places 60m apart from the neutron source in order to minimize the background from the neutron source.P-violating asymmetries were successfully observed at the level of 10^<-4> in p-wave resonances of various nuclei. The results gave us information on a systematics of the enhancement mechanism which depends upon the nuclear mass number and resonance character.

超热中子与原子核的相互作用包括原子核光学势的弹性散射和共振吸收。复合共振在超热能区域中彼此很好地解析，而重核的共振在较高能量区域中重叠。尽管在共振得到很好解析的情况下，横波贡献占主导地位，但观察到 p 波共振的贡献很小。宇称破坏效应可以在复合共振的寿命期间累积。奇偶校验违规的增强被解释为两个相反奇偶校验幅度之间干扰的结果，例如s 波和 p 波振幅。宇称破缺增强机制的研究对于可能的T破缺实验非常重要。通过中子传输法在铀、钍、铟、银的p波共振中测量了入射中子螺旋性的P破缺不对称性洛斯阿拉莫斯 LAMPF 的国际科学研究计划中使用了铌。在洛斯阿拉莫斯，使用了由 NH_3 珠组成的纵向偏振质子过滤器以获得纵向偏振中子束。使用装载^<10>B的液体闪烁体以便在几百eV的能量区域中以非常高的计数率检测中子。还使用测量捕获伽马射线的方法来检测小的p波共振洛斯阿拉莫斯有足够的精度。为了最小化中子源的背景，建造了CsI、BaF_2和GSO的伽马射线探测器，并将其放置在距中子源60m的地方。在p中10^<-4>水平成功地观察到了P破缺不对称性。 -各种原子核的波共振。结果为我们提供了有关取决于核质量数和共振特性的增强机制的系统学信息。