Speaker
Description
Precision $\beta$-decay measurements are a highly sensitive probe of beyond Standard Model (BSM) physics that aim to constrain non-standard charge changing weak currents at TeV scales. With the level of accuracy being approach by current experiments, it is important to have comparably accurate theoretial predictions of observable quantities within the Standard Model. Thus, one requires an accurate understanding of the underlying nuclear dynamics as well as of recoil corrections arising to the small momentum dependence of the nuclear matrix elements. We aim to achieve such an understanding by approaching the problem of nuclear $\beta$-decay with quantum Monte Carlo (QMC) methods, which allow one to solve the many-body Schrödinger equation while retaining the full complexity of the nuclear system. In this talk, I will provide an overview of {\it ab initio} calculations of $\beta$-decay using QMC and the Norfolk local chiral interaction (NV2+3) plus its consistent electroweak currents. In particular, I will discuss validation of the NV2+3 via the calcultion of Gamow-Teller matrix elements and strengths. After presenting this validation, I will detail a recent calculation of the $^6$He beta decay spectrum with the NV2+3 that retains the important recoil corrections. Within the NV2+3 model uncertainty and the parameter space presently allowed by experimental analyses, next-generation experiments would have a sensitivity to signatures from BSM charge-changing weak currents and from sterile neutrinos with masses near 1 MeV.
