Survey of deformation in nuclei in order to estimate the enhancement of sensitivity to atomic EDM

TL;DR

This survey identifies promising octupole-deformed nuclei, including isotopes like $^{229}$Pa, as potential candidates for atomic EDM experiments to explore CP-violation beyond the Standard Model.

Contribution

It provides a comprehensive list of long-lived, octupole-deformed nuclei suitable for future EDM measurements, expanding the options beyond previously studied isotopes like $^{225}$Ra.

Findings

Identified several viable isotopes for EDM experiments, including $^{229}$Pa and $^{223,225}$Rn.

Highlighted the importance of nuclear deformation in enhancing EDM sensitivity.

Pointed out the need for measuring parity doublet energy differences in certain isotopes.

Abstract

The observed baryon asymmetry of the universe (BAU) cannot be explained by the known sources of charge-parity (CP)-violation in the Standard Model (SM). A non-zero permanent electric-dipole-moment (EDM) for fundamental particles, nuclei or atoms, violates CP. Measuring a non-zero EDM allows us to gain a handle on additional sources of CP-violation required to explain the observed BAU. The EDM of an atom with an octupole and quadrupole deformed nucleus is enhanced. Therefore, the search for such atoms has become important in the quest to measure an EDM. Viability of EDM searches in $^{225}$Ra atoms with a deformed nucleus have already been demonstrated. We have performed a comprehensive survey for possible EDM candidates from a list of octupole deformed nuclei predicted by various theoretical models. Our search of long-lived isotopes with nuclear deformations comparable to or better than $^{225}$Ra results in a handful of viable candidates for future atomic EDM experiments based out of the Facility for Rare Isotope Beams (FRIB): $^{221}$Rn, $^{221,223,227}$Fr, $^{221,223,225}$Ra, $^{223,225,227}$Ac, $^{229}$Th, and particularly $^{229}$Pa. Furthermore, nuclei of $^{223,225}$Rn, $^{225}$Fr and $^{226}$Ac are also highly quadrupole and octupole deformed, but their ground state parity doublet energy difference has not yet been measured.