Radiative corrections to Gamow-Teller decays

TL;DR

This paper discusses an additional radiative correction to Gamow-Teller decays, affecting CKM unitarity tests and the extraction of the V_{ud} element, with implications for new physics and lattice QCD comparisons.

Contribution

It introduces a new radiative correction to Gamow-Teller form factors, analyzing its impact on neutron and mirror decays and refining V_{ud} measurements.

Findings

Significant effects on V_{ud} extraction from mirror decays.

Implications for right-handed current limits.

Enhanced understanding of radiative corrections in weak decays.

Abstract

Radiative corrections in the electroweak sector constitute an essential component in the ability to disentangle Beyond Standard Model physics from experimental data. This is particularly relevant for strongly bound systems undergoing weak decays such as nuclear $\beta$ decay, where its contribution to top-row CKM unitarity tests is essential. In this Letter we note the need for an additional radiative correction to the Gamow-Teller form factor in allowed decays. It concerns a combination of electrostatic final state interactions and QCD-induced currents. We review the basic derivation and report analytical results. Due to differences in their theoretical treatment in the literature, effects on the neutron and mirror systems are distinct. Significant consequences appear for a comparison of the former with lattice QCD, while changes occur in the $|V_{ud}|$ extraction in the latter. We discuss new limits on right-handed currents and provide a new value for $|V_{ud}|$ from mirror decays.