25th European Conference on Few-Body Problems in Physics

Constraining fundamental physics from ab initio nuclear theory

Not scheduled

20m

AudiMax (Alte Mensa)

Poster Presentation Poster Session

Speaker

Michael Gennari (University of Victoria)

Description

Recent global analysis of Fermi decays within a dispersion relation framework and the corresponding $V_{ud}$ determination have revealed tension with the Standard Model (SM) expectation of Cabibbo-Kobayashi-Maskawa (CKM) matrix unitarity, theoretical confirmation of which would indicate a deficiency within the SM weak sector. Extracting $V_{ud}$ requires electroweak radiative corrections (EWRC) from theory to be applied to the experimentally obtained $ft$-values. Novel calculations of the pieces sensitive to hadronic structure, i.e., the $\gamma W$-box, are at the heart of the recent tension. Moreover, to further improve on the extraction of $V_{ud}$, a modern and consistent treatment of the two nuclear structure dependent corrections is critical. These corrections are (i) ${\delta }_C$, the isospin symmetry breaking correction (ii) ${\delta }_{NS}$, the EWRC representing evaluation of the $\gamma W$-box on a nucleus. Preliminary estimations of ${\delta }_{NS}$ have been made in the dispersion relation framework, however the approach cannot include effects from low-lying nuclear states which require a true many-body treatment. Via collaboration with C.Y. Seng and M. Gorshteyn and use of the Lanczos continued fraction method, these corrections are now calculable within the ab initio no-core shell model (NCSM). The NCSM is a nonrelativistic quantum many-body theory for describing low-lying bound states of $s$- and $p$-shell nuclei starting solely from nuclear interactions. We will present preliminary results for ${\delta }_{NS}$ and ${\delta }_C$ determined in the NCSM for the ${}^{10}\text{C}\to {}^{10}\text{B}$ beta transition, with the eventual goal of extending the calculations to ${}^{14}\text{O}\to {}^{14}\text{N}$ and ${}^{18}\text{Ne}\to {}^{18}\text{F}$.