Search for the rare decays ${\mathit{K}}_{\mathit{L}}^0$→μe and ${\mathit{K}}_{\mathit{L}}^0$→ee

A search for the rare decays ${\mathit{K}}_{\mathit{L}}^0$→μe and ${\mathit{K}}_{\mathit{L}}^0$→ee was performed at the KEK 12-GeV Proton Synchrotron. No event was observed in the fiducial region for the decay ${\mathit{K}}_{\mathit{L}}^0$→μe. There was one event in the fiducial region for the decay ${\mathit{K}}_{\mathit{L}}^0$→ee, which was indistinguishable from the background. The upper limits on the branching ratios at 90% confidence level were B(${\mathit{K}}_{\mathit{L}}^0$→μe)<9.4×${10}^{\mathrm{-}11}$ and B(${\mathit{K}}_{\mathit{L}}^0$→ee)<1.6×${10}^{\mathrm{-}10}$.