Search for the lepton flavour violating decay B⁺ → K⁺μ^-τ⁺ using B^*0_s2 decays

A search is presented for the lepton flavour violating decay B$^{+}$ → K$^{+}$μ$^{−}$τ$^{+}$ using a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb$^{−1}$. The τ leptons are selected inclusively, primarily via decays with a single charged particle. The four-momentum of the τ lepton is determined by using B$^{+}$ mesons from $ {B}_{s2}^{\ast 0}\to {B}^{+}{K}^{-} $ decays. No significant excess is observed, and an upper limit is set on the branching fractionℬ(B$^{+}$ → K$^{+}$μ$^{−}$τ$^{+}$) < 3.9 × 10$^{−5}$ at 90 %  confidence level.The obtained limit is comparable to the world-best limit.[graphic not available: see fulltext]