CP violation experiment at Fermilab

The E731 experiment at Fermilab has searched for ''direct'' CP violation in K0 → ππ, which is parametrized by var-epsilon '/var-epsilon. For the first time, in 20% of the data set, all four modes of the KL,S → π+π- (π0π0) were collected simultaneously, providing a great check on the systematic uncertainty. The result is Re(var-epsilon '/var-epsilon) = -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 fine Δφ = -0.3 degrees ± 2.4 degree(stat) ± 1.2 degree(syst). Using this together with the world average φ±, we fine that the phase of the K0-bar K0 mixing parameter var-epsilon is 44.5 degree ± 1.5 degree. Both of these results agree well with the predictions of CPT symmetry. 17 refs., 10 figs