Precise Q Values for Ultra-Low Energy and Highly Forbidden Beta Decays Using Penning Trap Mass Spectrometry

对物理科学中极端现象的研究往往提供了新的发现和见解。在这个项目中，PI将研究放射性衰变的一个极端极限：以非常低的能量发生的贝塔衰变。这些衰变很有趣，因为它们可以在实验中用来确定中微子(也在β衰变中发射的轻的中性粒子)的质量，还因为它们需要对原子电子对核衰变过程的影响进行更详细的理论描述。到目前为止，只观察到了一次超低能量的β衰变(铟-115)。还有许多其他潜在的候选者，但母核和子核的原子质量还不够精确，无法确定所提出的衰变是否真的会发生。在这个项目中，PI将使用彭宁陷阱质谱仪对低能β衰变系统进行精确的原子质量测量。这项技术包括用磁场和电场限制离子，然后测量陷阱中的离子回旋频率；根据回旋频率可以确定原子质量。实验将在密歇根州立大学和中央密歇根大学(CMU)进行，为CMU的本科生和博士生提供实验核物理技术培训。核β衰变等弱衰变过程对我们理解核物理、原子和粒子物理做出了重大贡献。它们继续有助于我们理解天体物理过程、核结构、基本对称性和中微子的性质。非常罕见的弱衰变过程，如高度禁忌、超低Q值和双β衰变，对于研究中微子的粒子性质和质量标度，模拟和理解甚低计数率实验的背景，以及检验核β衰变的理论描述都是重要的。在拟议的工作中，PI将使用稀有同位素束设施(FRIB)的LEBIT对潜在的超低能量β衰变系统的Q值进行精确测量。感兴趣的衰变发生在母体核素的基态和子体的激发态之间，能量为1keV。拟议的测量将有助于确定可能出现超低Q值衰变的同位素。这些同位素可以用于未来的中微子质量实验，也将对这些极端衰变的核理论进行有意义的测试，在这些极端衰变中，原子干扰效应预计将发挥重要作用。这项工作将由博士和本科生完成。该奖项反映了NSF的法定使命，并通过使用基金会的学术价值和更广泛的影响审查标准进行评估，被认为值得支持。

The study of extreme phenomena in the physical sciences has often provided new discoveries and insights. In this project the PI will investigate one extreme limit of radioactive decays: beta-decays that occur with very low energy. These decays are interesting because they can be used in experiments to determine the mass of the neutrino (the light, neutral particle that is also emitted in beta-decay) and because they require the development of a more detailed theoretical description of the effect of atomic electrons on the nuclear decay process. To date, only one ultra-low energy beta decay has been observed (that of Indium-115). There are many other potential candidates, but the atomic masses of the parent and daughter nuclei are not known precisely enough to determine whether the proposed decay can actually occur. In this project the PI will perform precision atomic mass measurements of low energy beta decay systems using Penning trap mass spectrometry. The technique involves confining ions with magnetic and electric fields and then measuring the ion cyclotron frequency in the trap; from which atomic mass can be determined. Experiments will take place at Michigan State University and at Central Michigan University (CMU), providing training in experimental nuclear physics techniques for undergraduate and Ph.D. students at CMU.Weak decay processes such as nuclear beta-decay have provided significant contributions to our understanding of nuclear, atomic and particle physics. They continue to be of interest to aid our understanding of astrophysical processes, nuclear structure, fundamental symmetries, and properties of the neutrino. Very rare weak decay processes, such as highly forbidden, ultra-low Q value, and double-beta decays are important for investigating the particle nature and mass scale of the neutrino, modelling and understanding the background in very low count rate experiments, and for testing theoretical descriptions of nuclear beta-decay. In the proposed work, the PI will perform precise measurements of Q values for potential ultra-low energy beta-decay systems using LEBIT at the Facility for Rare Isotope Beams (FRIB). The decays of interest occur between the ground state of the parent nuclide and an excited state in the daughter with an energy of 1 keV. The proposed measurements will help to identify isotopes that are potential candidates for ultra-low Q value decays. These isotopes could be used in future neutrino mass experiments and will also be important for enabling meaningful tests of nuclear theory for these extreme decays where atomic interference effects are expected to play a significant role. The work will be performed by Ph.D. and undergraduateThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.