Search for the lepton-flavour violating decays $B^+ \to K^+ {\mu}^{\pm} e^{\mp}$

TL;DR

This study searches for lepton-flavour violating decays of B+ mesons into K+ and mixed muon-electron pairs using LHCb data, setting new upper limits that surpass previous constraints by over tenfold.

Contribution

It provides the most stringent upper limits to date on the branching fractions of B+ to K+ muon-electron decays, using proton-proton collision data at 7 and 8 TeV.

Findings

No significant signal observed.

Upper limits on branching fractions are set.

Results improve previous limits by over an order of magnitude.

Abstract

A search for the lepton-flavour violating decays $B^+ \to K^+ {\mu}^{\pm} e^{\mp}$ is performed using a sample of proton-proton collision data, collected with the LHCb experiment at centre-of-mass energies of $7$ and $8~{\rm TeV}$ and corresponding to an integrated luminosity of 3$\rm~fb^{-1}$. No significant signal is observed, and upper limits on the branching fractions are set as $\mathcal{B}(B^+ \to K^+ {\mu}^- e^+) < 7.0~(9.5) \times 10^{-9}$ and $\mathcal{B}(B^+ \to K^+ {\mu}^+ e^-) < 6.4~(8.8) \times 10^{-9}$ at 90 (95) % confidence level. The results improve the current best limits on these decays by more than one order of magnitude.