Search for Lepton-Flavor Violating Decays B^{+}→K^{+}μ^{±}e^{∓}.

A search for the lepton-flavor violating decays B + → K + μ ± e ∓ is performed using a sample of proton-proton collision data, collected with the LHCb experiment at center-of-mass energies of 7 and 8 TeV and corresponding to an integrated luminosity of 3     fb − 1 . No significant signal is observed, and upper limits on the branching fractions are set as B ( B + → K + μ − e + ) < 7.0 ( 9.5 ) × 10 − 9 and B ( B + → K + μ + e − ) < 6.4 ( 8.8 ) × 10 − 9 at 90% (95)% confidence level. The results improve the current best limits on these decays by more than one order of magnitude.