Review of the NA48 CP violation measurements with neutral and charged kaons

The main results on the CP violation measurements with neutral and charged kaons from the NA48 experiment at the CERN SPS are reviewed in this paper. The direct CP violating parameter Re(ε′/ε) has been measured by NA48 from the decay rates of neutral kaons into pion pairs. The final result, based on the data collected in 1997, 1998, 1999 and 2001, clearly established the existence of direct CP violation. NA48 also measured the CP violation parameter |η+−|, defined as the amplitude ratio of CP violating to CP conserving neutral kaon decays into two charged pions: |η+−| = A(KL → ππ)/A(KS → ππ). The CP violating decay KS →πππ has been studied by the NA48/1 experiment, using the data taken in 2000 and 2002 with a KS beam at high intensity. Only direct CP violation occurs in charged kaon decays, since mixing is not allowed. NA48/2 measured the Dalitz plot asymmetry of K →3π decays from the data collected in 2003 and 2004, setting a new limit on the asymmetry in the decay matrix slope parameters. Based on the same data sample, the result on the search for direct CP violation in the decay rate asymmetry in K →ππ γ processes is also presented.