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，即弱相互作用和电磁相互作用结合的有效性，提供重要的信息。温伯格-萨拉姆理论（标准模型）预测原子中的粒子、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，在一个比宇称守恒大得多的背景下，搜索一个非常微小的明显违反宇称的效应。电子和原子核之间的弱中性电流的影响可以在原子序数较大的原子中检测到，因为发现这种影响大致与Z^3成正比。我们测量了铊和铅原子在光跃迁中的宇称非守恒旋光度。结果与目前基于标准模型的计算结果一致。此外，对更小的与自旋相关的核旋转振幅设定了限制。这也与包括核模拟矩贡献的理论估计相一致。我们正在研究Rb原子超精细结构中宇称不守恒对微波跃迁的影响。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，在标准模型之外对物理进行限制。

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.