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

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 ${\hat{I}}^2$-asymmetry parameter ($A_{\hat{I}}^2$) and the ${\hat{I}}^2-\hat{I}½$ angular correlation ($a_{{\hat{I}}^2\hat{I}½}$). The recoil-order correction is calculated with the well-known Holstein formalism using the impulse approximation to evaluate experimentally inaccessible form factors. For the ${\hat{I}}^2-\hat{I}½$ angular correlation previously unpublished, semi-analytical radiative correction values are tabulated.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.

16 pages, 10 figures