A review of the latest CPLEAR results on T violation and CPT invariance in the neutral-kaon system

The CPLEAR experiment has studied the symmetries which may exist between matter and antimatter by comparing the time evolution of K 0 and K 0 . A number of measurements allowed the determination, with high precision and in a rather complete way, of the parameters of the time evolution and the related symmetry properties. T and CPT could be disentangled from CP and the first direct measurement of T violation was performed. The CPT invariance was directly tested through the parameter Re(δ), while Im(δ) was best determined from the Bell-Steinberger relation. The K 0 and K 0 mass and decay width differences were then bound to less than a few times 10 −18 GeV.