Isospin-symmetry-breaking corrections to superallowed Fermi beta decay: Formalism and schematic models

TL;DR

This paper develops a formalism to incorporate isospin-symmetry-breaking corrections in superallowed Fermi beta decay analysis, showing no first-order corrections and refining previous models with schematic assessments.

Contribution

It introduces a new formalism for isospin-symmetry-breaking corrections and evaluates existing models using schematic nuclear models.

Findings

No first-order isospin-symmetry-breaking corrections to nuclear matrix elements.

Refined corrections to Towner and Hardy's treatment.

Assessment of corrections with increasing schematic model complexity.

Abstract

We study the formalism to include isospin-symmetry-breaking corrections when extracting the up-down Cabibbo-Kobayashi-Maskawa matrix element from superallowed 0+ -> 0+ nuclear beta decay. We show that there are no first order isospin-symmetry-breaking corrections to the relevant nuclear matrix elements. We find corrections to the treatment of Towner and Hardy, and assess these using schematic models of increasing complexity.