Precise Penning Trap Measurements to Aid Searches for Ultra-low Q Value Beta-decay Candidates

Central Michigan University, Mount Pleasant MI

Investigators

Abstract

The neutrino is a very light and weakly interacting particle. Nevertheless, its characteristics are of great interest to fields as diverse as particle physics and cosmology. The exact mass of the neutrino is currently unknown, but is needed to help develop a complete theoretical description of the fundamental particles that exist in nature, and to determine how the neutrino has affected the evolution of the cosmos. There are several experiments underway that aim to determine the mass of the neutrino via the beta-decay of an unstable parent isotope to a daughter isotope. In this research, the PI and team of students will identify additional isotopes that could be used for these experiments. The isotopes that the PI’s team is searching for have very low energy (Q-value) decays. The decay energies can be calculated using known energy levels in the daughter isotope and the atomic mass of the parent and daughter isotopes. However, in many cases where a so-called ultra-low Q value decay might be possible, the mass of the parent and daughter isotopes are often not known precisely enough to determine whether the decay is actually energetically allowed. The PI’s team will perform precise mass measurements to enable the identification of potential ultra-low Q value decay candidates. As part of this project, the PI will invite a cohort of six high school students to CMU each summer for a two-week summer school in which they will learn the basic concepts of experimental nuclear physics and work with undergraduate students to become involved in the team’s research projects. Weak decay processes such as nuclear beta-decay have provided significant contributions to our understanding of nuclear, atomic and particle physics. Very rare weak decay processes, such as ultra-low Q value beta-decays, which are the focus of this project, could be important for investigating the mass scale of the neutrino, and for testing theoretical descriptions of nuclear beta-decay. In this project, the PI and team of students will perform precise measurements of Q values for potential ultra-low Q value beta-decay candidates using Penning trap mass spectrometry facilities at National Laboratories, such as LEBIT at the Facility for Rare Isotope Beams (FRIB) and the Canadian Penning Trap at Argonne National Laboratory (ANL). These decays 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 determination experiments, and are also 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 undergraduate students at CMU, providing opportunities for training at a world leading research facility. This 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.