Identifying ideal nuclei in which to search for CP violating moments: Necessity to populate nuclear levels and characterize their nuclear deformation

Abstract

New sources of CP violation, beyond the known sources in the standard model (SM) via the CKM matrix, are required to explain the baryon asymmetry of the universe. Measurement of P,T violating moments, such as the electric dipole moment (EDM) or the magnetic quadrupole moment (MQM), of sub-atomic particles like the neutron or the electron as well as of atoms, serves as powerful tools with which to probe sources of CP violation. Quadrupole and octupole deformation of nuclei can significantly enhance the atomic EDM by many orders of magnitude compared to that with a spherical nucleus. In this white paper, we identify deformed isotopes in which to measure an EDM or an MQM. Furthermore, we also clearly identify a subset of these isotopes where measurements involving characterization of their level scheme and nuclear deformation parameters are necessary. (A section in the low energy white paper of the 2022 NSAC Long Range Planning exercise.)