ε′ε results from NA48 and KTeV E832 Original Research Article

After more than 25 years of intense experimental effort, the parameter View the MathML source which characterizes direct CP violation in the neutral kaon system has been accurately measured by both the Fermilab KTeV E832 and the Cern NA48 experiments. The latest results presented here demonstrate unambiguosly the existence of direct CP violation. The experimental challenge is reviewed, and the techniques used to extract the parameter are discussed. The current situation is given and future propects are briefly sketched.