Measurement of the branching ratio and a study of CP for the leptonic decay ${\mathit{K}}_{\mathit{L}}$→${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$

We have determined the branching ratio of ${\mathit{K}}_{\mathit{L}}$→${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ based on the observation of 27 four-electron final state events with 0.36 estimated background event, B(${\mathit{K}}_{\mathit{L}}$→${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$) =[3.96±0.78(stat)±0.32(syst)]×${10}^{\mathrm{-}8}$. Using the distribution of the angle between the ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ pair decay planes, we find that the decay proceeds predominantly through the ${\mathit{K}}_2$(CP=-1) state.