Study of $K_{e4}$ decays in the NA48/2 experiment at CERN

Large samples of kaon decays have been collected in 2003-2004 by the NA48/2 collaboration in the charged $(K^{±} \to \pi^+ \pi^- e^{±} \nu)$ and neutral $(K^{±} \to \pi^0 \pi^0 e^{±} \nu)$ $K_{e4}$ modes. In the charged mode, form factors have been extensively studied from a sample of more than one million decays and a preliminary branching ratio measurement is reported here. In the neutral mode, a sample of 44 000 decays has been analyzed and provides a new branching ratio value with 1-2% precision, a factor of ten improvement with respect to the current knowledge. Both modes contribute to the study of low energy QCD and are powerful tests of Chiral Perturbation Theory predictions.