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arXiv · 2608.22845

$\Delta$ resonance contributions to QED radiative corrections in neutron and inverse beta decay

Oleksandr Tomalak·Yi-Bo Yang
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Abstract

We incorporate the $\Delta(1232)$ resonance into pion-induced QED radiative corrections to neutron decay and inverse beta decay (IBD). Within the framework of heavy-baryon chiral perturbation theory with explicit $\Delta$ degrees of freedom, we compute additional contributions and study their impact on IBD cross sections and on the renormalization of the nucleon isovector vector and axial-vector charges. $\Delta$ resonance does not renormalize the vector charge. For the axial-vector charge, including the $\Delta$ resonance restores power counting and significantly reduces the QED radiative correction to the experiment-over-lattice-QCD ratio $g_A/\left(g^\mathrm{QCD}_A g_V\right)$, bringing it to zero within radiative-correction uncertainties. $\Delta$ resonance increases the pion-induced QED radiative corrections to IBD by a factor $1.2$-$1.3$.

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Oleksandr Tomalak, Yi-Bo Yang. 2026-08-24. $\Delta$ resonance contributions to QED radiative corrections in neutron and inverse beta decay. https://arxiv.org/abs/2608.22845

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