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arXiv · 2604.03090

The form factor expansion in the precision $\beta$ decay era

Leendert Hayen
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Abstract

Precision tests of the Standard Model using $\beta$ decay have always relied on a careful choice of transition to minimize residual nuclear structure uncertainties. Following breakthroughs in nucleon-level radiative corrections in the last decade, however, corrections due to nuclear structure are once more a limiting factor in several scenarios. Progress in ab initio nuclear theory provides a path forward, but common recoil-order approximations in traditional formalisms often go unnoticed. Here, we critically examine their origin and address recently resolved and identify open questions.

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Leendert Hayen. 2026-04-03. The form factor expansion in the precision $\beta$ decay era. https://arxiv.org/abs/2604.03090

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