The EPR-type strangeness correlation in the K K system produced in the reaction pp ™ K K at rest has been tested using the CPLEAR detector. The strangeness was tagged via strong interaction with absorbers away from the creation point. The results are consistent with the QM non-separability of the wave function and exclude a spontaneous wave-function Ž . factorisation at creation CL ) 99.99% . q 1998 Elsevier Science B.V.

We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of K 0 0 0 transforming into K and K into K as a function of the neutral-kaon eigentime t. The comparison is based on the analysis of the neutral-kaon semileptonic decays recorded in the CPLEAR experiment. There, the strangeness of the neutral kaon at ". 0 0 was measured over the interval 1 tt-20 t , thus leading to evidence for time-reversal non-invariance.

We use ts to recent published CPLEAR data on neutral kaon decays to + and e to constrain the CPT{violation parameters appearing in a formulation of the neutral kaon system as an open quantum-mechanical system. The obtained upper limits of the CPT{violation parameters are approaching the range suggested by certain ideas concerning quantum gravity.

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