NA48∕2 Results and NA62 Perspectives

Abstract

Recent results on rare and radiative Κ± decays from the NA48/2 experiment are reported. Among many rare decay modes, the analysis of Κ±→π+π−e±ν (Κe4) decays allows a quasi model‐independent approach to the study of low energy ππ scattering. With more than 1 million Κe4 decays the form factors and their energy dependence are measured with an improved precision. In the channel Κ±→π±π0γ more than 1 million decays were reconstructed, leading to the first measurement of the interference between direct photon emission and inner bremsstrahlung contributions as well as new limits on CP violation. For Κ±→π±γγ, a precise measurement of the branching fraction was performed, based on more than 1000 events. In addition the perspectives of NA62 to measure the branching ratio of the very rare kaon decay Κ+→π+νν¯ at the CERN SPS are described.