Benchmarking isosopin symmetry breaking in ab initio nuclear theory via the isobaric multiplet mass equation in T = 1 superallowed β decay systems

Abstract

Searching for physics Beyond the Standard Model (BSM) has become a central focus in physics research over the past few decades. One way to do this is through precision measurements of superallowed 0+ → 0+ Fermi β decay. These decays give the most precise measurements of the vector coupling constant of the weak interaction, an important step in calculating the up-down element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. CKM unitarity, if broken, would imply significant physics BSM. However, the extraction of the vector coupling constant assumes perfect isospin symmetry in nuclei, requiring theoretical isospin symmetry breaking (ISB) corrections to be applied. The ISB corrections can be calculated using ab initio nuclear many body methods using interactions from chiral effective field theory. However, before these corrections can be used reliably for BSM physics searches, they must be benchmarked against known results. In this Thesis, ab initio methods are used to calculate the coefficients of the isobaric multiplet mass equation (IMME) for T = 1 superallowed 0+ → 0+ Fermi β decay systems. The implications of the IMME coefficients to ISB corrections are also discussed.