A. Apostolakis

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.

Experimental determination of the energy generated in nuclear cascades by a high energy beam

An already existing, sub-critical arrangement made of natural uranium and water moderator has been exposed to a low intensity (≈ 109 ppp) proton beam from CERN-PS at several kinetic energies from 600 MeV to 2.75 GeV. The energy delivered by the hadronic cascade induced by the beam in the device has been measured by the temperature rise of small sampling blocks of uranium located in several different positions inside the device and counting the fissions in thin probe foils of natural uranium. We find typically G ≈ 30 in reasonable agreement with calculations, where G is the ratio of the energy produced in the device to the energy delivered by the beam. This result opens the way to the realisation of the so-called Energy Amplifier, a practical device to produce energy from thorium or depleted uranium targets exposed to an intense high energy proton beam. Results show that the optimal kinetic is ≥ 1 GeV, below which G decreases but is still acceptable in the energy range explored

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.

Experimental verification of neutron phenomenology in lead and transmutation by adiabatic resonance crossing in accelerator driven systems

Energy and space distributions of spallation neutrons (from 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3 x 3.3 x 3 m3 lead volume and neutron capture rates on long-lived fission fragments 99 Tc and 129 I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.

Cross sections of common final states for K−p interactions at 8.25 GeV/c

Abstract Topological and channel cross sections are given for the more common final states produced in K − p interactions at 8.25 GeV/ c together with the single particle inclusive cross sections. We present cross sections for prominent resonances occurring in final states K N (nπ) and find the resonance fractions to be roughly independent of multiplicity.

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.

New experimental limits on νμ→νe oscillations

Abstract The results of an experiment which searched for ν e events arising from oscillations of a low-energy ν μ beam are presented. The BEBC heavy liquid bubble chamber, placed at a distance of 825 m from an external proton target at the CERN PS, was used as a neutrino detector. The appearance of ν e CC interactions provides a sensitive indication of ν μ → ν e oscillations. 470 ν μ CC events and 4 ν e events, with an estimated background of 3 ν c CC events, have been observed. The resulting limits on the oscillation parameters are: δm 2 ⩽0.09 eV 2 (for maximal mixing) and sin 2 θ ⩽0.013 for δm 2 =2.2 eV 2 , at the 90% confidence level.

NEW EXPERIMENTAL LIMITS ON muon-neutrino ---> electron-neutrino OSCILLATIONS

Abstract The results of an experiment which searched for ν e events arising from oscillations of a low-energy ν μ beam are presented. The BEBC heavy liquid bubble chamber, placed at a distance of 825 m from an external proton target at the CERN PS, was used as a neutrino detector. The appearance of ν e CC interactions provides a sensitive indication of ν μ → ν e oscillations. 470 ν μ CC events and 4 ν e events, with an estimated background of 3 ν c CC events, have been observed. The resulting limits on the oscillation parameters are: δm 2 ⩽0.09 eV 2 (for maximal mixing) and sin 2 θ ⩽0.013 for δm 2 =2.2 eV 2 , at the 90% confidence level.

A measurement of the S- and P-wave content of antiproton annihilation at rest into two pions in liquid deuterium

Abstract Based on our measurement of the ratio f(π − π 0 p ) f(π + π − n ) =2.07±0.05 for antiproton annihilation at rest in liquid deuterium, we find that S-wave annihilation of the antiproton on the proton or neutron into ππ is dominant. We quote a 95% confidence level upper limit of 8% for P-wave annihilation into ππ.