High precision study of K+- --> 3pi+- decays by NA48/2

Preliminary results of study of K ± → 3� ± decays by the NA48/2 experiment at CERN SPS are presented. They include a precise measurement of the direct CP violating charge asymmetry of Dalitz plot linear slope parameters Ag = (g + −g )/(g + + g ), and a measurement of the Dalitz plot slope parameters (g,h,k) themselves. Due to the design of the experiment, and a large data set collected, unprecedented precisions were achieved.