KL → π0ηη experiment at KEK12-GeV PS — E391a

Abstract The K L → π 0 η η decay is one of the most attractive phenomena for the study of the CP violation. The branching ratio can be calculated with a small theoretical ambiguity, which will provide a clean determination of a basic parameter of the present particle physics. It will also play an important role for the search of the new physics as well as for the fundamental unerstanding of the CP-violation. We will start a kind of pilot experiment using a present 12-GeV proton synchrotron (PS) at KEK from early 2004, which is the first dedicated experiment searching for the K L → π 0 η η decay.