Search for the lepton-flavour violating decays B 0 → K *0 μ ± e ∓ and Bs0 → ϕμ ± e ∓

Abstract

A search for the lepton-flavour violating decays B0 → K∗0µ ±e ∓ and B0 s → φµ±e ∓ is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of 9 fb−1 . No significant signals are observed and upper limits of B(B 0→ K∗0µ +e −) < 5.7 × 10−9 (6.9 × 10−9 ), B(B 0→ K∗0µ −e +) < 6.8 × 10−9 (7.9 × 10−9 ), B(B 0→ K∗0µ ±e ∓) < 10.1 × 10−9 (11.7 × 10−9 ), B(B 0 s → φµ±e ∓) < 16.0 × 10−9 (19.8 × 10−9 ) are set at 90% (95%) confidence level. These results constitute the world’s most stringent limits to date, with the limit on the decay B0 s → φµ±e ∓ the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.