Kaon physics at CERN: Recent results by NA48/2 experiment

NA48/2 is devoted to study direct CP violation in three charged pions kaon decay. A novel design for the beam line and an upgrade of the NA48 detector are adopted to allow the simultaneous detection of decays from $K^{+}/K^{−}$ unseparated beams. The first preliminary measurement of the direct CP violating parameter Ag is presented. A value for the charge asymmetry in the $K^{\pm} \rightarrow \pi^{\pm}\pi^{+}\pi^{-}$ of Ag $= (0.5 \pm 3.8) \times 10^{−4}$ has been measured using using 1.6 billions $K^{+}/K^{−}$ decays. The analysis of the charge asymmetry in the “neutral” channel $K^{\pm} \rightarrow \pi^{\pm}\pi^{0}\pi^{0}$ and a new method to extract the $\pi\pi$ scattering length studying accurately the Dalitz Plot in the “neutral” mode are also shortly discussed. The future program on kaon physics at CERN is briefly outlined.