Search for lepton flavor-violating decay modes $B^0\to K^{\ast 0}\ddot{I}{„}^{\pm }{\ell }^{\mp }$ ($\ell =e,\hat{I}¼$) with hadronic B-tagging at Belle and Belle II

Abstract

We present the results of a search for the charged-lepton-flavor violating decays $B^0\to K^{\ast 0}\ddot{I}{„}^{\pm }{\ell }^{\mp }$, where ${\ell }^{\mp }$ is either an electron or a muon. The results are based on 365 fb${}^{-1}$ and 711 fb${}^{-1}$ datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic $B$-tagging technique, and search for a signal decay in the system recoiling against a fully reconstructed $B$ meson. We find no evidence for $B^0\to K^{\ast 0}\ddot{I}{„}^{\pm }{\ell }^{\mp }$ decays and set upper limits on the branching fractions in the range of $(2.9-6.4)\times 10^{-5}$ at 90% confidence level.

19 pages, 4 figures