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

Abstract

A search for the lepton-flavour violating decays B 0 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 B 0 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 \( \frac{@}{@}\mathrm{\mathcal{B}}\left({B}_s^0\to {e}^{\pm }{\mu}^{\mp}\right)<6.3(5.4)\times 1{0}^{-9} \) and \( \frac{@}{@}\mathrm{\mathcal{B}}\left({B}_s^0\to {e}^{\pm }{\mu}^{\mp}\right)<7.2(6.0)\times 1{0}^{-9} \) at 95% (90%) confidence level, respectively. The upper limit on the branching fraction of the B0e±μ decay is also evaluated, obtaining \( \frac{@}{@}\mathrm{\mathcal{B}}\left({B}^0\to {e}^{\pm }{\mu}^{\mp}\right)<1.3(1.0)\times 1{0}^{-9} \) at 95% (90%) confidence level. These are the strongest limits on these decays to date.

A preprint version of the article is available at ArXiv.

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