CP-conserving and -violating contributions to ${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$νν¯

We study both CP-conserving and -violating contributions to the decay ${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^{+}$ ${\mathrm{\pi }}^{\mathrm{-}}$νν¯. We find that the decay branching ratio is dominated by the CP-conserving part. In the standard CKM model, we estimate that for ${\mathit{m}}_{\mathit{t}}$∼174 GeV, the branching ratio due to the CP-conserving (-violating) contributions can be as large as 4.4×${10}^{\mathrm{-}13}$ (1.0×${10}^{\mathrm{-}14}$).