Speaker
Description
Radiative corrections from nuclear structure effects are a key theoretical input to precision extractions of $V_{ud}$ from superallowed $0^{+}\hspace{-2pt}\rightarrow 0^{+}$ beta decays, and currently limit the sensitivity of CKM unitarity tests to new physics. We present a formalism to compute two-body transition densities in medium-mass nuclei using deformed coupled-cluster theory and its extensions, enabling ab initio calculations of the nuclear-structure-dependent correction $\delta_{\mathrm{NS}}$ across all relevant superallowed emitters with stable daughter nuclei. These calculations incorporate two-body currents derived consistently from chiral effective field theory, and are benchmarked against quantum Monte Carlo results in light nuclei. We discuss how this approach supports efforts to better quantify theoretical uncertainties in $\delta_{\mathrm{NS}}$, and its broader utility for electroweak processes involving two-body operators, including $0\nu\beta\beta$ decay.
