Superallowed Fermi transitions in RPA with a relativistic point-coupling energy functional

TL;DR

This paper uses a relativistic RPA approach with a point-coupling energy functional to evaluate isospin symmetry-breaking corrections in superallowed Fermi transitions, testing CKM matrix unitarity with high precision.

Contribution

It introduces a self-consistent relativistic RPA method with a point-coupling functional to calculate symmetry-breaking corrections in Fermi transitions, impacting CKM unitarity tests.

Findings

Calculated symmetry-breaking corrections are consistent across different functionals.

Sum of CKM matrix elements deviates from unitarity by about 0.1%.

Method provides a reliable framework for precision tests of the Standard Model.

Abstract

The self-consistent random phase approximation (RPA) approach with the residual interaction derived from a relativistic point-coupling energy functional is applied to evaluate the isospin symmetry-breaking corrections {\delta}c for the 0+\to0+ superallowed Fermi transitions. With these {\delta}c values, together with the available experimental ft values and the improved radiative corrections, the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is examined. Even with the consideration of uncertainty, the sum of squared top-row elements has been shown to deviate from the unitarity condition by 0.1% for all the employed relativistic energy functionals.