On the Coulomb corrections in nuclear beta decay

TL;DR

This paper develops a Lorentz-invariant framework for calculating Coulomb corrections in nuclear beta decay, updating known results and exploring new contributions from non-standard interactions, with implications for T-odd correlations.

Contribution

It introduces a novel on-shell amplitude method for beta decay, enabling precise calculations of Coulomb corrections and T-odd correlations, including subleading effects and non-standard interactions.

Findings

Updated numerical values for Coulomb contributions to the D parameter.

Calculated new subleading contributions in the presence of non-standard interactions.

Identified additional T-odd correlation coefficients generated in the Standard Model.

Abstract

We propose a Lorentz invariant and little group covariant description of beta decay amplitudes relying on on-shell amplitude methods and the spinor variables for massive particles. The framework is employed to calculate Coulomb corrections to the decay amplitude and their contribution to T -odd correlation coefficients, including the D parameter. In the SM limit we recover the known results for the Coulomb contributions to D and update their numerical values. We also calculate new subleading contributions to D in the presence of non-standard scalar and tensor interactions. We also point out that two other T -odd correlation coefficients are generated in the SM at the same order as the D parameter, and provide their numerical values for selected transitions.