Ultrahigh-Sensitivity Search for an Electric Dipole Moment of^<129>Xe atom by Means of Nuclear Spin Maser with Artificial Feedback

CP不变性的破坏，在中性K衰变中已经存在了40多年，最近在B衰变中也得到了证实，仍然是当代粒子物理学的重要课题之一。标准模型（SM）在K- m矩阵元素中以复相的形式包含CP违逆，并很好地代表了观察到的改变味道的K和B衰变，但从未提供可检测大小的永久电偶极矩（EDM）。另一方面，在SM之外提出的模型，如超对称模型，预测了相当大的电火花加工值，从而使电火花加工成为超越SM的物理探索的独特地位。本研究旨在开发一种能够精确测定自旋进动频率的核自旋脉泽新方案，为在^<129>Xe原子中超高灵敏度地寻找EDM铺平道路。利用光抽运铷蒸气的自旋交换，成功地极化了22 mm直径玻璃池中Xe气体的^<129>Xe核自旋，用探针激光检测了它们的进动，并首次观察到人工反馈的自维持进动。观测到的频率精度随着测量时间T的变化Δv∝1/T^<1.5>，直到T = 3000 s才趋于平缓。根据这一结果，我们在设置上进行了一些改进，包括磁屏蔽、磁电流稳定、激光操作和波长稳定以及电池温度控制，最终在测量时间T = 30000 s内达到Δv = 9.3 hz（相当于EDM灵敏度Δd ~ 9×10^<-28> ecm）。此外，还发现了一些对v精度有决定性影响的问题，这些问题绝对值得进一步改进。因此，我们得出结论，本工作证实了新方法在原子电火花加工搜索中的有效性，并明确了实现期待已久的电火花加工精度的方向。

Violation of CP invariance, known for more than 40 years in neutral K decay and recently confirmed also in B decay, remains one of vital subjects in contemporary particle physics. The standard Model (SM) includes the CP violation in a form of complex phase in the K-M matrix elements and well represents the observed flavor-changing K and B decays, but never provide a permanent electric dipole moment (EDM) of detectable size. On the other hand, models proposed beyond the SM, such as supersymmetric one, predict sizeable values for EDM, thus rendering EDM an exclusive position as a probe of physics beyond the SM. The present research has aimed at development of new scheme of nuclear spin maser that enables precision determination of spin precession frequency, in order to pave a route for ultrahigh-sensitivity search for an EDM in a ^<129>Xe atom.^<129>Xe nuclear spins of Xe gas contained in a 22 mm-diameter glass cell were successfully polarized by spin exchange with optically pumped Rb vapor, their precession was detected by probe Laser light, and a self-sustaining precession by means of an artificial feedback was observed for the first time. The observed precision in frequency proved to improve as Δv ∝ 1/T^<1.5> as a function of the measurement time T until T = 3000 s, and then tended to be flattened. Following this result, we worked out several improvements in the setup, including the magnetic shielding, magnet current stabilization, Laser operation and wavelength stabilization, and cell temperature control, and finally attained Δv = 9.3 nHz (amounting to EDM sensitivity of Δd 〜 9×10^<-28> ecm) in a measurement time T = 30000 s. Also, a number of issues were identified that have decisive effects on the v precision and definitely deserve further work for improvement. We thus conclude that the present work has confirmed effectiveness of novel method for the atomic EDM search, and has clarified the directions that should enable the long awaited EDM precision.