Search for the lepton number violating decays $B^{+}\to \pi^- \mu^+ \mu^+$ and $B^{+}\to K^- \mu^+ \mu^+$

TL;DR

This paper reports a search for lepton number violating decays of B+ mesons into a negatively charged hadron and two muons, setting new upper limits that significantly improve previous constraints, with no signal observed.

Contribution

First search for these specific lepton number violating decays using LHCb data, establishing the most stringent limits to date.

Findings

No evidence of the decays was found.

Upper limits on branching fractions were set at 5.4×10⁻⁸ and 5.8×10⁻⁸.

Limits improved by factors of 40 and 30 over previous results.

Abstract

A search is performed for the lepton number violating decay $B^{+}\to h^- \mu^+ \mu^+$, where $h^-$ represents a $K^-$ or a $\pi^-$, using data from the LHCb detector corresponding to an integrated luminosity of $36pb^{-1}$. The decay is forbidden in the Standard Model but allowed in models with a Majorana neutrino. No signal is observed in either channel and limits of $B(B^{+} \to K^- \mu^+ \mu^+) < 5.4\times 10^{-8}$ and $B(B^{+} \to \pi^- \mu^+ \mu^+) < 5.8\times 10^{-8}$ are set at the 95% confidence level. These improve the previous best limits by factors of 40 and 30, respectively.