Search for the rare decay \[{{{B} ^+}} \!\rightarrow {\mu ^+} {\mu ^-} {\mu ^+} {{\upnu } _\mu } \]

Abstract

A search for the rare leptonic decay \[{{{B} ^+}} \!\rightarrow {\mu ^+} {\mu ^-} {\mu ^+} {{\upnu } _\mu } \] is performed using proton-proton collision data corresponding to an integrated luminosity of \[4.7 \, {\hbox {fb}}^{-1}\] collected by the LHCb experiment. The search is carried out in the region where the lowest of the two \[{\mu ^+\mu ^-} \] mass combinations is below \[980 {\mathrm {\,MeV\!/}c^2} \]. The data are consistent with the background-only hypothesis and an upper limit of \[1.6 \times 10^{-8}\] at 95% confidence level is set on the branching fraction in the stated kinematic region.