O. Behnke

First direct observation of time-reversal non-invariance in the neutral-kaon system

Abstract We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of K 0 transforming into K0 and K0 into K 0 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 time t=0 was tagged by the kaon charge in the reaction p p → K ± π ∓ K 0 ( K 0 ) at rest, whereas the strangeness of the kaon at the decay time t=τ was tagged by the lepton charge in the final state. An average decay-rate asymmetry 〈 R( K 0 t=0 → e + π − ν t=τ )−R( K 0 t=0 → e − π + ν t=τ ) R( K 0 t=0 → e + π − ν t=τ )+R( K 0 t=0 → e − π + ν t=τ ) 〉=(6.6±1.3 stat ±1.0 syst )×10 −3 was measured over the interval 1 τ S τ S , thus leading to evidence for time-reversal non-invariance.

An EPR experiment testing the non-separability of the wave function

Abstract The EPR-type strangeness correlation in the K0 K 0 system produced in the reaction p p → K 0 K 0 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 factorisation at creation (CL >99.99%).

Tests of CPT symmetry and quantum mechanics with experimental data from CPLEAR

Abstract We use fits to recent published CPLEAR data on neutral kaon decays to π + π − and πeν 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.

Physics at CPLEAR

LEAR offered unique opportunities to study the symmetries which exist between matter and antimatter. At variance with other approaches at this facility, CPLEAR was an experiment devoted to the study of , and symmetries in the neutral-kaon system. A variety of measurements allowed us to determine with high precision the parameters which describe the time evolution of the neutral kaons and their antiparticles, including decay amplitudes, and the related symmetry properties. Limits concerning quantum-mechanical predictions (EPR, coherence of the wave function) or the equivalence principle of general relativity have been obtained. An account of the main features of the experiment and its performances is given here, together with the results achieved.

\(\mathrm{\cal T}\)-violation and \(\mathrm{\cal CPT}\)-invariance measurements in the CPLEAR experiment: a detailed description of the analysis of neutral-kaon decays to \(\mathrme \pi \nu\)

Abstract. A detailed description of the analysis of neutral kaons decaying to

Evaluation of the phase of the CP violation parameter η+− and the KL - KS mass difference from a correlation analysis of different experiments

mathrme pi nu

Measurement of the neutral kaon regeneration amplitude in carbon at momenta below 1 GeV/c

is given, based on the complete set of data collected with the CPLEAR experiment. Using a novel approach involving initially strangeness-tagged

CPLEAR results on the CP parameters of neutral kaons decaying to π+π−π0

mathrm{K^0}

Experimental measurement of the KSKSKSKL ratio in antiproton annihilations at rest in gaseous hydrogen at 15 and 27 bar

and

An upper limit for the branching ratio of the decay K

mathrm{overline{K}}{}^0