Search for the lepton-flavour violating decays $B^{+}\to \ddot{I}{€}^{+}\hat{I}{¼}^{\pm }{e}^{\mp }$

Abstract

The first search for the lepton-flavour violating decays $B^{+}\to \ddot{I}{€}^{+}\hat{I}{¼}^{\pm }{e}^{\mp }$ in proton-proton collisions is presented, using data collected by the LHCb experiment between 2011 and 2018, corresponding to an integrated luminosity of 9 fb${}^{-1}$. No significant signal is observed and an upper limit on the branching fraction is set at $\mathcal{B}(B^{+}\to \ddot{I}{€}^{+}\hat{I}{¼}^{\pm }{e}^{\mp })<1.8\times 10^{-9}$ at the $90\%$ confidence level, two orders of magnitude more restrictive than the current world average. This is the first constraint on lepton-flavour violating $b\to d$ quark transitions at the LHC and also sets the most stringent upper limits to date on $b\to d\hat{I}{¼}^{\pm }{e}^{\mp }$ transitions. Limits on left-handed and scalar scenarios beyond the Standard Model are also reported.

All figures and tables, along with any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/6012/ (LHCb public pages)