Influence of the recoil-order and radiative correction on the beta decay correlation coefficients in mirror decays

TL;DR

This paper analyzes how recoil-order and radiative corrections affect beta decay correlation coefficients, providing calculations and tables to improve the precision of experimental tests of the Standard Model in mirror decays.

Contribution

It offers a detailed calculation of recoil-order and radiative corrections for beta decay correlations, including new semi-analytical radiative correction tables for mirror decays.

Findings

Recoil-order corrections vary among isotopes up to A=45.

Radiative corrections are tabulated for the first time for the beta-nu angular correlation.

Comparison of corrections across isotopes aids future experimental planning.

Abstract

Measurements of the beta decay correlation coefficients in nuclear decay aim for a precision below $1\%$ and theoretical predictions should follow this trend. In this work, the influence of the two dominant Standard Model correction terms, i.e. the recoil-order and the radiative correction, are studied for the most commonly measured beta correlations, i.e. the $\beta$-asymmetry parameter ($A_{\beta}$) and the $\beta-\nu$ angular correlation ($a_{\beta \nu}$). The recoil-order correction is calculated with the well-known Holstein formalism using the impulse approximation to evaluate experimentally inaccessible form factors. For the $\beta-\nu$ angular correlation previously unpublished, semi-analytical radiative correction values are tabulated. Results are presented for the mirror beta decays up to $A=45$. We examine the effect of both corrections and provide a comparison between different isotopes. This comparison will help planning, analysing, and comparing future experimental efforts.