Sterile neutrinos and $R_K$

TL;DR

This paper investigates how sterile neutrinos can cause violations of lepton flavor universality in light meson decays, potentially explaining deviations in decay ratios while remaining consistent with experimental bounds.

Contribution

It introduces a model with sterile neutrinos affecting meson decay ratios and demonstrates compatibility with current experimental constraints.

Findings

Sterile neutrinos can enhance decay ratio deviations at tree level.

The inverse seesaw model can saturate current experimental bounds.

Results align with existing experimental and observational constraints.

Abstract

We study the violation of lepton flavour universality in light meson decays due to the presence of non-zero mixings between the active neutrinos with new sterile states. The modified $W \ell \nu$ vertices, arising from a non-unitarity leptonic mixing matrix intervening in charged currents, might lead to a tree-level enhancement of $R_{P} = \Gamma (P \to e \nu) / \Gamma (P \to \mu \nu)$, with $P=K, \pi$. These enhancements are illustrated in the case of the inverse seesaw, showing that one can saturate the current experimental bounds on $\Delta r_{K}$ (and $\Delta r_{\pi}$), while in agreement with the different experimental and observational constraints.