Measurement of Parity Nonconservation in Ytterbium

镱宇称不守恒的测量

• 批准号: 0758031
• 负责人: Dmitry Budker
• 金额: $ 48.3万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2012-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0758031&HistoricalAwards=false
• 关键词: Measurement; Parity; Nonconservation; Ytterbium

The study of parity nonconservation (PNC) in ytterbium is motivated by the opportunity to probe physics within the atomic nucleus using modern table-top laser-spectroscopy techniques. Atomic PNC experiments are a unique and powerful tool for the study of fundamental nuclear and particle interactions. This is exemplified by the discovery of the nuclear anapole moment (an electromagnetic multipole that violates parity) and the measurement of the parity violating electron-nucleon interaction in cesium to 0.35% accuracy. In atomic ytterbium, the PNC amplitude is enhanced by two orders of magnitude compared to that in cesium. This facilitates measurements of the anapole moments of two nonzero-nuclear-spin isotopes of ytterbium. Furthermore, the broad range of stable ytterbium isotopes is attractive for measuring the variation of neutron radii along an isotopic chain. This project aims at measuring PNC effect in ytterbium to an accuracy exceeding that obtained for cesium.The intellectual merit of this project is that it may resolve inconsistencies between the theory and measurements of the parity violating weak nuclear interactions and will provide complementary information that is exceedingly difficult to access by other means. These experiments will also yield information on variation of the mean-square neutron radii in a chain of isotopes, which in addition to being a fundamental test of nuclear theory, pins down the density dependence of the symmetry energy of neutron-rich nuclear matter which has impacts on neutron star structure and heavy ion collisions. Importantly, neither the anapole-moment measurement nor the neutron-distribution measurement relies on high-precision theory, although atomic calculations accurate to better than 15% are required to extract the nuclear anapole. The broader impact of an ytterbium PNC experiment extends to a variety of different fields besides atomic, nuclear and particle physics. The theoretical and experimental tools developed for the PNC experiment have an essential significance for projects employing ytterbium for studies of quantum degenerate gases and novel optical frequency standards. New experiments using ultra-cold ytterbium atoms to search for the nuclear electric dipole moment would benefit from the information obtained in this work. A broad international collaboration within this project established between the UC Berkeley group and a number of universities in Europe, Russia, Australia, and India will contribute to new advances in this field and to exchange of new ideas and development of novel experimental techniques. As in the ongoing work, several graduate and undergraduate students will continue to play key roles in the research and collaborations.

研究镱的宇称不守恒（PNC）的动机是利用现代桌面激光光谱技术探测原子核内的物理。原子PNC实验是研究基本核与粒子相互作用的一种独特而有力的工具。举例来说，核拟极矩（违反宇称的电磁多极矩）的发现，以及对铯中违反电子-核子相互作用的宇称的测量，精度达到0.35%。在原子镱中，PNC振幅比在铯中提高了两个数量级。这有助于测量两种非零核自旋同位素的拟极点矩。此外，稳定的镱同位素范围广泛，对于测量沿同位素链的中子半径变化具有吸引力。本项目旨在测量镱中的PNC效应，使其精度超过铯。这个项目的智力价值在于，它可以解决违反弱核相互作用的宇称的理论和测量之间的不一致，并将提供通过其他方式极其难以获得的补充信息。这些实验还将获得同位素链中均方中子半径变化的信息，这除了是核理论的基本测试外，还确定了富含中子的核物质的对称能对中子星结构和重离子碰撞的影响的密度依赖性。重要的是，模拟极矩测量和中子分布测量都不依赖于高精度理论，尽管提取核模拟极需要精确到15%以上的原子计算。一个镱PNC实验的更广泛的影响延伸到各种不同的领域，除了原子，核和粒子物理。为PNC实验开发的理论和实验工具对利用镱研究量子简并气体和新型光学频率标准的项目具有重要意义。利用超冷镱原子寻找原子核电偶极矩的新实验将受益于这项工作中获得的信息。在这个项目中，加州大学伯克利分校与欧洲、俄罗斯、澳大利亚和印度的一些大学建立了广泛的国际合作，这将有助于在这一领域取得新的进展，并促进新思想的交流和新实验技术的发展。在正在进行的工作中，一些研究生和本科生将继续在研究和合作中发挥关键作用。