Fundamental symmetry tests with the francium laser trap facility at ISAC

使用 ISAC 的钫激光陷阱设施进行基本对称性测试

• 批准号: SAPPJ-2018-00027
• 负责人: Gwinner, Gerald
• 金额: $ 12.38万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=693970
• 关键词: Fundamental; symmetry; tests; francium; laser

The fundamental forces of nature are one of the fascinating subjects that can be studied at ISAC, Canada's radioactive beam facility at TRIUMF. In particular, the weak force, causing the beta-decay of nuclei, is unique in exhibiting the phenomenon of parity-violation: The mirror images of physical processes mediated by the weak force are not observed in nature. ISAC offers a unique possibility to study atomic parity non-conservation in francium (Fr), an element combining a very heavy nucleus (Z=87) with the simple, essentially hydrogenlike, valence structure of an alkali. Fr nuclei are the least stable among the first 103 elements in the periodic table, the longest-lived isotope decays in only 23 minutes. To make optimum use of the minute sample, the Fr atoms are slowed down with laser light and captured into a magneto-optic laser trap, suspended in free space at temperatures millions of times colder than room temperature. Together with researchers from the United States and Mexico, including 3 graduate students, one postdoctoral fellow, and several undergraduate research students, we have established a francium trapping facility at ISAC and have carried out first measurements with trapped Fr atoms, concerning the distribution of magnetization inside the nucleus in a string of isotopes. In a next step, we are now setting up experiments using precise laser and microwave spectroscopy to ultimately study atomic parity non-conservation in francium. The microwave experiment will measure a parity non-conserving effect inside the nucleus known as the anapole moment. To date, only measurements in one isotope of cesium and thallium each have been performed, and more data is crucial for a better understanding of hadronic parity non-conservation in nuclear matter. The laser experiment will search for 'new' physics outside the - so far very successful - Standard Model of particle physics by measuring nuclear-spin independent atomic parity non-conservation in francium. The project offers outstanding opportunities for the broad training of highly qualified personnel.

自然的基本力是可以在 ISAC（加拿大 TRIUMF 的放射性束设施）研究的引人入胜的课题之一。特别是，引起原子核β衰变的弱力在表现宇称破坏现象方面是独一无二的：在自然界中没有观察到由弱力介导的物理过程的镜像。 ISAC 为研究钫 (Fr) 中的原子宇称不守恒提供了独特的可能性，钫是一种将非常重的原子核 (Z=87) 与简单的、本质上类似氢的碱金属价结构结合在一起的元素。 Fr 原子核是元素周期表前 103 种元素中最不稳定的，寿命最长的同位素仅在 23 分钟内衰变。为了充分利用微小样品，Fr 原子被激光减速并捕获到磁光激光陷阱中，悬浮在比室温低数百万倍的自由空间中。我们与来自美国和墨西哥的研究人员（包括 3 名研究生、1 名博士后研究员和几名本科生）一起在 ISAC 建立了钫捕获设施，并对捕获的 Fr 原子进行了首次测量，涉及一系列同位素中原子核内磁化强度的分布。下一步，我们正在使用精确的激光和微波光谱进行实验，以最终研究钫的原子宇称不守恒性。微波实验将测量原子核内的宇称非守恒效应，称为阿纳极矩。迄今为止，仅对铯和铊的一种同位素进行了测量，更多的数据对于更好地理解核物质中的强子宇称不守恒至关重要。激光实验将通过测量钫中与核自旋无关的原子宇称不守恒性，在迄今为止非常成功的粒子物理标准模型之外寻找“新”物理。该项目为高素质人才的广泛培训提供了绝佳的机会。