Search for the lepton-flavour violating decays B (s) 0 → e ± μ ∓

Abstract

A search for the lepton-flavour violating decays B0 s → e ±µ ∓ and B0 → e ±µ ∓ is performed based on a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 , collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yields are consistent with the background-only hypothesis. Upper limits on the branching fraction of the B0 s → e ±µ ∓ decays are evaluated both in the hypotheses of an amplitude completely dominated by the heavy eigenstate and by the light eigenstate. The results are B(B0 s → e ±µ ∓) < 6.3 (5.4) × 10−9 and B(B0 s → e ±µ ∓) < 7.2 (6.0) × 10−9 at 95% (90%) confidence level, respectively. The upper limit on the branching fraction of the B0 → e ±µ ∓ decay is also evaluated, obtaining B(B0 → e ±µ ∓) < 1.3 (1.0) × 10−9 at 95% (90%) confidence level. These are the strongest limits on these decays to date