Search for the lepton-flavour-violating decays B0 → K*0τ±e∓

A bstract A first search at LHCb for the lepton-flavour-violating decays B 0 → K *0 τ ± e ∓ is presented. The analysis is performed using a sample of proton-proton collision data, collected with the LHCb detector at a centre-of-mass energy of 13 TeV between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb − 1 . No significant signal is observed, and upper limits on the branching fractions are determined to be B(B⁰→ K⁰τ⁻e⁺)<5.9(7.1)× 10⁻⁶ B B 0 → K ∗ 0 τ − e + < 5.9 7.1 × 10 − 6 and B(B⁰→ K⁰τ⁺e⁻)<4.9(5.9)× 10⁻⁶ B B 0 → K ∗ 0 τ + e − < 4.9 5.9 × 10 − 6 at the 90% (95%) confidence level. These results correspond to the current most stringent upper limits for b → sτl transitions.