T and CPT violation in the neutral-kaon system

The CPLEAR experiment measured decay rates of initially pure strangeness-tagged neutral kaons into hadronic and semileptonic final states. From these decay rates, parameters describing T and CPT violation have been measured to a high precision: Analysing semileptonic decays makes it possible to tag the kaon strangeness at the decay time and thus to compare K/sup 0/ to K/sup 0/ and K/sup 0/ to K/sup 0/ transition rates. The observed failure of this detailed balance is a direct measurement of the time-reversal asymmetry. CPT- violation parameters are also measured directly from semileptonic decays. A global fit using the Bell-Steinberger unitarity relation gives an even more stringent limit on possible CPT violation in the neutral-kaon system and confirms that the observed asymmetry is a pure T-violation effect. (12 refs).