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

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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.