Limit on the branching ratio of ${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^0$${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$

We report the results of a search for the decay ${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^0$ ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ conducted by E799 at Fermilab. The largest contribution to this decay mode is expected to be CP violating. Observations of this decay could either confirm the standard model mechanisms for CP violation or point to physics beyond the standard model. No such events were seen in our search. The 90% confidence level upper limit is determined to be B(${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^0$ ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$)<4.3×${10}^{\mathrm{-}9}$.