Test of Chiral Perturbation Theory in kaon decays

This paper presents results obtained by the CERN experiment NA48/2. Sample of 7146K±→π±e+e− decays, of 1164K±→π±γγ events and of 120K±→π±γe+e− events have been collected with small background contamination. Branching ratio and form factors for three different models have been obtained for K±→π±e+e−, plus a model-independent branching ratio. In addition, the first measurement of the direct CP violating asymmetry has been performed. A measurement of the branching ratio has been obtained for K±→π±γγ, and kinematic distributions have been compared to ChPT expectations. Finally, the branching ratio of K±→π±γe+e− has been measured in the kinematically accessible region, representing the first observation of such a decay.