CP-violating decayKL0→π0νν¯

The process $K_L^0$→${\pi }^0$νν¯ offers perhaps the clearest window yet proposed into the origin of CP violation. The largest expected contribution to this decay is a direct CP-violating term at ≊few×${10}^{\mathrm{-}12}$. The indirect CP-violating contribution is some 3 orders of magnitude smaller, and CP-conserving contributions are also estimated to be extremely small. Although this decay has never been directly probed, a branching ratio upper limit of ∼1% can be extracted from previous data on $K_L^0$→2${\pi }^0$. This leaves an enormous range in which to search for new physics. If the Kobayashi-Maskawa (KM) model prediction can be reached, a theoretically clean determination of the KM product sin${\theta }_2$sin${\theta }_3$sinδ can be made.