Unique forbidden beta decays at zero momentum transfer

TL;DR

This paper investigates how electromagnetic radiative corrections can enable forbidden nuclear beta decays at zero momentum transfer, significantly impacting precision tests of the Standard Model and new physics searches.

Contribution

It introduces the effect of electromagnetic corrections on forbidden beta decays, revealing a new decay channel at zero recoil not previously considered.

Findings

Electromagnetic corrections enable forbidden decays at zero momentum transfer.

The decay spectrum is significantly altered by these corrections.

Implications for precision Standard Model tests and new physics searches.

Abstract

We report an exploratory study of the $\mathcal{O}(\alpha)$ structure-dependent electromagnetic radiative corrections to unique first-forbidden nuclear beta decays. We show that the insertion of angular momentum into the nuclear matrix element by the virtual/real photon exchange opens up the decay at vanishing nuclear recoil momentum which was forbidden at tree level, leading to a dramatic change in the decay spectrum not anticipated in existing studies. We discuss its implications for precision tests on the Standard Model and searches for new physics.