# Majorana neutrinos with effective interactions in B decays

## TL;DR

This paper explores how Majorana neutrinos could influence B meson decays within an effective interaction framework, providing new bounds on their properties from LHCb and Belle data, and improving constraints on related new physics models.

## Contribution

It introduces a comprehensive effective interaction analysis of Majorana neutrinos in B decays, deriving more stringent bounds than previous studies, especially for higher neutrino masses.

## Key findings

- Stronger bounds on Majorana neutrino interactions from B decay data.
- Identification of the impact of Majorana neutrinos on leptonic number violation signals.
- Enhanced constraints on new physics models like Left-Right symmetric models.

## Abstract

We investigate the possible contribution of Majorana neutrinos to $B$ meson decays in an effective interaction formalism, in the mass range $0.5$ GeV $<m_N<5 $ GeV. We study the decay of the $B^-$ meson via $B^- \to \mu^- \mu^- \pi^+$ at LHCb, which is a signal for leptonic number violation and the presence of Majorana neutrinos, and put bounds on different new physics contributions, characterized by their Dirac-Lorentz structure. We also study the bounds imposed by the radiative $B$ decay ($B^- \rightarrow \mu^- \nu \gamma$) results from Belle. The obtained bounds are more restrictive than previous values found for dimension 6 four-fermion contact vectorial and scalar Majorana neutrino interactions in the context of the Left-Right symmetric model for higher Majorana masses at the LHC, showing that the direct calculation of the effective $N$ interactions contribution to different processes can help to put more stringent bounds to different UV-complete models parameterized by an effective Lagrangian.