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

A first search at LHCb for the lepton-flavour-violating decays B⁰ → K^∗0τ^±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 → K^∗0τ⁻e⁺) < 5.9 (7.1) × 10⁻⁶ and B(B⁰ → K^∗0τ⁺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.