Speaker
Description
Searching for a low-lying doublet state to calibrate the new physics sensitivity of protactinium-229: New sources of charge-parity (CP) violation are thought to be needed in order to explain the absence of antimatter in the visible universe. The observation of a non-zero nuclear Schiff moment would be a sign of both parity and time-reversal violation, and therefore CP-violation as well, via the CPT theorem. Pear-shaped nuclei, such as Ra-225, enhance the observable effect of symmetry violations by a factor of 1,000 or more compared to relatively non-deformed nuclei like Hg-199. Pa-229 is also thought to be pear-shaped and may have a low-lying excited state on the order of 100 eV above the ground state. If this doublet state exists and has opposite parity but the same spin as the ground state, it could enhance the sensitivity to symmetry violations by a factor of over 1,000,000 compared to Hg-199. I will review the nuclear structure status of Pa-229 and outline our plans to search for the parity doublet state using two complementary methods: internal conversion (IC) electron spectroscopy and low-energy gamma spectroscopy. The IC electron spectroscopy involves the use of a spectrometer adapted from the design of another spectrometer that was successfully used to measure an 8.4 eV state in Th-229. The gamma spectroscopy technique involves an extreme ultraviolet optic coupled to a superconducting tunnel junction sensor in order to selectively detect only low-energy gammas. Both techniques require a U-229 beam that will eventually be available at the Facility for Rare Isotope Beams at Michigan State University. This work is supported by the PCLB Foundation. This work is also supported by the Gordon and Betty Moore Foundation, grant DOI 10.37807/GBMF13799. This material is also based upon work supported by the Department of Energy National Nuclear Security Administration through the Nuclear Science and Security Consortium under Award Number(s) DE-NA0003996.