Search for the lepton-flavour-violating decays $B^0 \to K^{*0} \tau^\pm e^\mp$

Abstract

A first search for the lepton-flavour-violating decays $B^0\to K^{*0}\tau^\pm e^\mp$ 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 $\cal{B}$$(B^0 \to K^{*0}\tau^-e^+)< 5.9$ $(7.1)\times 10^{-6}$ and $\cal{B}$$(B^0 \to K^{*0}\tau^+e^-)< 4.9$ $(5.9)\times 10^{-6}$ at the 90% (95%) confidence level.