Improved limit on the 225Ra electric dipole moment
Improved limit on the 225Ra electric dipole moment
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DOI：
10.1103/physrevc.94.025501
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发表时间：
2016-08-03
影响因子：
3.1
通讯作者：
Dietrich, Matthew R.
中科院分区：
文献类型：
--
作者：
Bishof, Michael;Parker, Richard H.;Dietrich, Matthew R.
背景：八极形变的原子核，如Ra-225，有望放大核介质中时间反转和宇称破坏相互作用产生的可观察到的原子电偶极矩。2015年，我们报道了第一次对Ra-225原子EDM的“原理证明”测量。目的：这项工作是几次实验升级中的第一次，以数量级提高我们的Ra-225 EDM测量的统计灵敏度，并评估有助于当前和未来实验灵敏度水平的系统效应。方法：激光冷却和捕获的Ra-225原子被保存在磁屏蔽环境中心的超高真空室中的两个高压电极之间。我们使用依赖于核自旋的激光光散射来观察均匀磁场中的Larmor进动，并寻找与外加电场成正比的相移，这表明EDM的存在。结果：我们对Ra-225原子EDM的测量结果小于1.4×10(-23)e cm(95%置信度上限)，比之前的结果提高了36倍。结论：我们对系统效应的评估表明，这种测量完全受到统计不确定度的限制。将这种测量技术与计划中的实验升级相结合，我们预计在1×10(-28)e厘米水平上具有统计灵敏度，在4×10(-29)e cm水平上具有总的系统不确定度。
Background: Octupole-deformed nuclei, such as that of Ra-225, are expected to amplify observable atomic electric dipole moments (EDMs) that arise from time-reversal and parity-violating interactions in the nuclear medium. In 2015 we reported the first "proof-of-principle" measurement of the Ra-225 atomic EDM.Purpose: This work reports on the first of several experimental upgrades to improve the statistical sensitivity of our Ra-225 EDM measurements by orders of magnitude and evaluates systematic effects that contribute to current and future levels of experimental sensitivity.Method: Laser-cooled and trapped Ra-225 atoms are held between two high-voltage electrodes in an ultrahigh-vacuum chamber at the center of a magnetically-shielded environment. We observe Larmor precession in a uniform magnetic field using nuclear-spin-dependent laser light scattering and look for a phase shift proportional to the applied electric field, which indicates the existence of an EDM. The main improvement to our measurement technique is an order-of-magnitude increase in spin-precession time, which is enabled by an improved vacuum system and a reduction in trap-induced heating.Results: We have measured the Ra-225 atomic EDM to be less than 1.4 x 10(-23) e cm (95% confidence upper limit), which is a factor of 36 improvement over our previous result.Conclusions: Our evaluation of systematic effects shows that this measurement is completely limited by statistical uncertainty. Combining this measurement technique with planned experimental upgrades, we project a statistical sensitivity at the 1 x 10(-28) e cm level and a total systematic uncertainty at the 4 x 10(-29) e cm level.