The final result on direct CP violation from the NA48 experiment

The NA48 experiment at CERN has recently obtained the final result on the $\epsilon '/\epsilon$ parameter, that quantifies direct CP violation in the $K^{0}-\bar{K^{0}}$ system. The total data sample, acquired during five years of data-taking, corresponds to 5.3 million $K_{L} \to \pi^{0}\pi^{0}$ decays. The result, $\Re(\epsilon '/\epsilon) =(14.7 \pm 2.2) \times 10^{-4}$, confirms unambiguously the occurrence of direct CP violation. Converting this number in a precision test of the standard model picture of CP violation is an open challenge for nonperturbative QCD calculations. (6 refs).