UNC-CH Physics and Astronomy Thesis Proposal Presentation

Evan Ney

“Improving the global description of beta decay.”

The study of astrophysical processes like supernovae explosions and element formation in the rapid neutron capture processes (r-process) requires reliable nuclear data for medium mass and heavy nuclei. In particular, reliable beta decay half-lives are highly desired as they play a dominant role in these processes. However, many of these exotic nuclei are too unstable to be produced in a lab and contain too many degrees of freedom to be computationally tractable for ab-initio nuclear theory.

Nuclear density functional theory (DFT) is one of the few theoretical methods which allows for self-consistent, microscopic calculations of nuclear properties across the entire nuclear chart. I will present my results for a new global DFT calculation of beta decay half-lives for almost 4000 neutron rich nuclei where odd-A and odd-odd nuclei are treated self-consistently in what is known as the equal filling approximation. I will then discuss how we can improve our global calculations by incorporating a more realistic account of the strong interaction during the beta decay. This can be accomplished using chiral effective field theory to expand the nuclear current, where at higher orders we obtain two-body currents accounting for pion exchange. It was recently shown that these two-body currents account for the majority of the quenching of the axial vector coupling, answering a long outstanding question in nuclear physics. I will explain how I plan to incorporate these two-body terms into our global beta decay calculations and what we can learn from doing so.