A precision measurement of direct CP violation in the decay of neutral kaons into two pions

The direct CP violation parameter $\Re(\epsilon '/ \epsilon)$ has been measured from the decay rates of neutral kaons into two pions using the NA48 detector at the CERN SPS. The 2001 running period data was collected under varied conditions compared to earlier years (1997-99). The new data result is $\Re(\epsilon '/ \epsilon) = (13.7 \pm 3.1) \times 10^{-4}$. The overall value of $\Re(\epsilon '/ \epsilon) = (14.7 \pm 2.2) \times 10^{-4}$ is obtained from the complete NA48 data set. (5 refs)