Possible Tests of Time Reversal Invariance in Beta Decay
Possible Tests of Time Reversal Invariance in Beta Decay
复制标题
Beta 衰变中时间反转不变性的可能测试
DOI：
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发表时间：
1957
期刊：
影响因子：
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通讯作者：
H. Wyld
中科院分区：
文献类型：
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作者：
J. Jackson;S. Treiman;H. Wyld
现在已经建立了β衰变过程在空间反射和电荷共轭下的不变性。然而，时间反转下的不变性仍然是一个悬而未决的问题。我们在这里讨论几种可能的检验这种对称运算有效性的方法。给出了三种实验情况下分布函数的一般表达式，这三种情况有可能在时间反转下探测到不变的允许β衰变项：(A)原子核定向并测量电子和中微子动量；(B)原子核没有取向，但观察到反冲动量、电子动量和极化；(C)原子核定向并测量电子动量和极化。得到的分布函数忽略了库仑扭曲效应和核子的相对论修正，但在其他方面是完全的。这样的实验应该允许，除了检测在时间反转下不变的项之外，还应该开始确定现在表征β衰变的十个复杂耦合常数。还发现了另一个令人惊讶的结果。如果Lee和Yang的两分量中微子理论是正确的，如果关于各种耦合常数的相对大小的某些可能合理的假设是有效的，那么即使是来自无取向核的允许β衰变中的电子的纵向极化也应该几乎是完全的(具体地说，等于c/c1)。
Noninvariance under space reflection and charge conjugation has now been established for beta decay processes. Invariance under time reversal remains an open question, however. We discuss here several possible tests for the validity of this symmetry operation. General expressions are given for the distribution function in three experimental situations, which have the possibility of detecting terms in allowed beta decay that are not invariant under time reversal: (a) experiments in which the nuclei are oriented and electron and neutrino momenta are measured; (b) experiments in which the nuclei are not oriented, but the recoil momentum and electron momentum and polarization are observed; (c) experiments in which the nuclei are oriented and the electron momentum and polarization are measured. The distribution functions obtained omit Coulomb distortion effects and relativistic corrections for the nucleons, but are otherwise complete. Such experiments should permit, in addition to the detection of terms which are not invariant under time reversal, the beginnings of a determination of the ten complex coupling constants which now characterize beta decay. An additional, somewhat surprising, result is found. If the two-component neutrino theory of Lee and Yang is correct, and if certain perhaps reasonable assumptions concerning the relative magnitudes of the various coupling constants are valid, then the longitudinal polarization of electrons in allowed beta decay even from unoriented nuclei should be almost complete (specifically, equal to c/cl.