Search for the Lepton-Flavor-Violating Decays B 0 s → e ± μ ∓ and B 0 → e ± μ ∓

Abstract

A search for the lepton-flavor-violating decays B 0 s → e ± μ ∓ and B 0 → e ± μ ∓ is performed with a data sample, corresponding to an integrated luminosity of 1.0

fb − 1 of p p collisions at √ s = 7

TeV , collected by the LHCb experiment. The observed number of B 0 s → e ± μ ∓ and B 0 → e ± μ ∓ candidates is consistent with background expectations. Upper limits on the branching fractions of both decays are determined to be B ( B 0 s → e ± μ ∓ ) < 1.1 ( 1.4 ) × 10 − 8 and B ( B 0 → e ± μ ∓ ) < 2.8 ( 3.7 ) × 10 − 9 at 90% (95%) confidence level (C.L.). These limits are a factor of 20 lower than those set by previous experiments. Lower bounds on the Pati-Salam leptoquark masses are also calculated, M LQ ( B 0 s → e ± μ ∓ ) > 101

TeV / c 2 and M LQ ( B 0 → e ± μ ∓ ) > 126

TeV / c 2 at 95% C.L., and are a factor of 2 higher than the previous bounds.