1211.3052 (A. Abada et al.)

Tree-level lepton universality violation in the presence of sterile
neutrinos: impact for $R_K$ and $R_π$    [PDF]

A. Abada, D. Das, A. M. Teixeira, A. Vicente, C. Weiland

We consider a tree-level enhancement to the violation of lepton flavour universality in light meson decays arising from modified $W \ell \nu$ couplings in the standard model minimally extended by sterile neutrinos. Due to the presence of additional mixings between the active (left-handed) neutrinos and the new sterile states, the deviation from unitarity of the 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 $P=K, \pi$. We illustrate these enhancements in the case of the inverse seesaw model, 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.

View original: http://arxiv.org/abs/1211.3052