Studies on Parity Non-conservation in Atomic Microwave Transitions

很明显，原子上的激光实验可以为基本粒子物理学中最关键的问题之一提供重要的信息，即，弱相互作用和电磁相互作用相结合的有效性。Weinberg-Salam理论（标准模型）预言了原子中的粒子、电子、质子和中子之间存在额外的弱相互作用。弱相互作用破坏宇称，而电磁相互作用保持宇称，因此，有可能建立一个实验，在比宇称守恒背景大得多的情况下，寻找一个非常微小的显式宇称破坏效应。在原子序数Z较大的原子中，电子与原子核之间的弱中性电流效应可以被探测到，因为这种效应与Z ^[3]大致成正比。我们测量了铊和铅原子光学跃迁的宇称非守恒旋光。这一结果与目前基于标准模型的计算结果一致。此外，限制已经设置在更小的核自旋相关的旋转振幅。这也与理论估计相一致，其中包括核的anapole moment.We现在正在研究宇称非守恒效应的超精细结构中的Rb原子的微波跃迁。此外，当实验结果与相关的原子计算相结合时，可以得出Zo玻色子的质量值，或者通过同位旋守恒参数S对标准模型之外的物理学进行限制。

It is clear that laser experiments on atoms can provide important information on one of the most crucial questions of elementary particle physics, i.e., the validity of combining weak interactions and electro-magnetic interactions. The Weinberg-Salam theory (Standard Model) predicts the existence of additional weak interactions between the particles, electrons, protons and neutrons which from an atom. The weak interaction violates parity while the Electro-magnetic interaction conserves it. Therefore, it is possible to set up an experiment to search a very tiny explicitly parity violating effect in the presence of a very much larger than parity conserving backgrounds. The effect of weak neutral currents between electrons and the atomic nucleus could be detected in atoms with large atomic numbers, Z,since the effect was found to be roughly proportional to Z^3.We measured parity nonconserving (PNC) optical rotation on the optical transition in atomic thalium and lead. The result is consistent with current calculations based on the standard model. Moreover, limits have been set on the much smaller nuclear spin-bependent rotation amplitude. This is also consistent with theoretical estimates which include a nuclear anapole moment contribution.We are now investigating parity nonconservation effect on the microwave transition in hyperfine structures of Rb atom. Furthermore, the experimental results, when combined with the relevant atomic calculations, lead to a value for the mass of the Zo boson or, alternatively, place a limit on physics beyond the standard model through the isospin-conserving parameter, S.