CP violation experiment at Fermilab

This paper reports on the E731 experiment at Fermilab that has searched for direct CP violation in K0 → ππ, which is parametrized by ε'/ε. For the first time all four of the KL,S → ππ modes were collected simultaneously for 20% of the data sample, provided great check on the systematic uncertainty. The result is Re(ε'/ε) = -0.0004 ± 0.0014(stat) ± 0.0006(syst), which provides no evidence for direct CP violation. The CPT symmetry has also been tested by measuring the phase difference Δφ = φ00 - φ+- between the two CP violating parameters η00 and η+-. We find Δφ = 0.3 degrees ± 2.4 degrees(stat) ± 1.2 degrees(syst). Using this together with the world average φ+-, we find that the phase of the K0 - bar K0 mixing parameter ε is 44.5 degrees ± 1.5 degrees. Both of these results agree well with the predictions of CPT symmetry