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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The quantum efficiency (QE) curves of five Philips XP2020Q photomultiplier tubes (PMTs) , one H amama t su R2059 PMT, and a Na-Salicylate coated glass window were determined using a calibrated Thorn EM1 9426 P M T as a reference. The QE of XP2020Q PMTs a t wavelengths smaller than 230 nm appears much better than the values specified by the manufacturer. Consequently, the often reported photon yield of 2000 photons/MeV for the fast component of the scintillation pulses from pure BaFz crystals determined with this tube is overestimated. Our results, obtained by means of calibrated equipment and using 662 keV-prays, yield a value of 1400 photons/hfeV.