Search for direct CP violation in charged kaon decays by NA48/2

After firmly establishing direct CP Violation in two pions decays of neutral kaons, the NA48 experiment at CERN-SPS has collected more than 1.6 billion of charged kaon decays into three charged pions, using a unique double beam technique which allows a high level of control on systematic effects.A preliminary result is presented on the direct CP violation Dalitz plot linear slope asymmetry parameter Ag, that corresponds to more than an order of magnitude improvement in precision with respect to previous experiments.