New NA48/2 Results on Rare Kaon Decays

NA48/2 results related to ChPT testing are presented. The most precise measurement of the charged kaon semileptonic form factors has been obtained from $4.4 \times 10^6$ the $K^{\pm} \rightarrow \pi^0e^{\pm}\nu_e (K^{\pm}_{e3})$ and $2.91 \times 10^6$ the $K^{\pm} \rightarrow \pi^{0} \mu^{\pm}\nu_{\mu} (K^{\pm}_{\mu 3})$ events collected in 2004. In addition, the branching ratio of the $K^{\pm} \rightarrow \pi^{\pm}\pi^0e^+e^-$ decay, that has not been observed so far, has been obtained from a sample of 4919 decay candidates with 4.9% background. The branching ratio in the full kinematic region is measured to be $(4.24 \pm 0.15) \times 10^{-6}$, which is in agreement with ChPT predictions.