Search for  \(B{}^0_s \rightarrow \ell ^{\mp } \tau ^{\pm }\) ( \(\ell = e,\mu \) ) with the Semi-leptonic Tagging Method at Belle

We present a search for the lepton flavor violating decays \(B{}^0_s \rightarrow \ell ^{\mp }\tau ^{\pm }\) ; \(\ell = e,\mu \) using the full data sample of 121.4 \(fb^{-1}\) of data recorded on \(\Upsilon (5S)\) resonance with the Belle detector at the KEKB asymmetric energy \(e^+e^-\) collider. We use events in which one \(B_{s}^{0}\) meson is reconstructed in a semileptonic decay mode and another meson is reconstructed in the signal mode. For this search, the \(\tau \) lepton is reconstructed from \(\tau ^+ \rightarrow e^+ \overline{\nu }_{\tau } \nu _{e}\) and \(\tau ^+ \rightarrow \mu ^+ \overline{\nu }_{\tau } \nu _{\mu }\) decay channels. We will set an upper limit on the branching fraction \(\mathcal {B}(UL)\) of these decays.