Comprehensive analysis of beta decays within and beyond the Standard Model

TL;DR

This paper provides a comprehensive review and analysis of nuclear and neutron beta decays, updating the values of fundamental parameters and setting new limits on exotic interactions within and beyond the Standard Model.

Contribution

It introduces new global fits incorporating mirror beta decay data, refining the understanding of beta decay interactions and constraining new physics beyond the Standard Model.

Findings

Confirmed the V-A structure of weak interactions

Updated values for V_ud and g_A at the 10^{-4} level

Set new limits on exotic neutrino couplings

Abstract

Precision measurements in allowed nuclear beta decays and neutron decay are reviewed and analyzed both within the Standard Model and looking for new physics. The analysis incorporates the most recent experimental and theoretical developments. The results are interpreted in terms of Wilson coefficients describing the effective interactions between leptons and nucleons (or quarks) that are responsible for beta decay. New global fits are performed incorporating a comprehensive list of precision measurements in neutron decay, superallowed $0^+\rightarrow 0^+$ transitions, and other nuclear decays that include, for the first time, data from mirror beta transitions. The results confirm the $V$-$A$ character of the interaction and translate into updated values for $V_{ud}$ and $g_A$ at the $10^{-4}$ level. We also place new stringent limits on exotic couplings involving left-handed and right-handed neutrinos, which benefit significantly from the inclusion of mirror decays in the analysis.