A detailed analysis of neutral kaons decaying to (cid:25) + (cid:25)(cid:0)(cid:25) 0 is presented based on the complete data set containing half a million events. Time-dependent decay rate asymmetries are measured between initially tagged K 0 and K 0 and for different regions of the phase space. These asymmetries, resulting from the interference between the CP-conserving decay amplitude of K L and the decay amplitude of K S – either CP-violating or CP-conserving – allow the determination of the K S parameters (cid:17)+ (cid:0) 0 (CP-violating) and (cid:21) (CP-conserving), and also of the main isospin components of the K S decay amplitude. The branching ratio of K S ! (cid:25) + (cid:25)(cid:0)(cid:25) 0 (CP-conserving) is deduced directly from (cid:21) . In addition, we extract the slope parameters describing the energy dependence of the K L ! (cid:25) + (cid:25)(cid:0)(cid:25) 0 Dalitz plot. The whole set of our results fits well within the current phenomenological picture of the neutral-kaon system including CP violation and Chiral Perturbation Theory (ChPT).

Ultra-High Energy Cosmic Rays (UHECR) (E ≥ 5 × 1019 eV ) are detected through Extensive Air Showers that are created when a primary cosmic ray particle interacts with the atmosphere of the Earth. The energy of the primary particle can be estimated experimentally based on simulations. In this paper, we attempt to estimate the energy of UHECR gamma ray photons by applying a Monte Carlo simulation code and we compare the results with the ones derived in our previous papers for hadron initiated showers. The scenario of simulations is adapted to the P. Auger Observatory site.

We summarize here the results of the TARC experiment whose main purpose is to demonstrate the possibility of using Adiabatic Resonance Crossing (ARC) to destroy efficiently Long-Lived Fission Fragments (LLFFs) in accelerator-driven systems and to validate a new simulation developed in the framework of the Energy Amplifier programme. An experimental set-up was installed in a CERN PS proton beam line to study how neutrons produced by spallation at relatively high energy (En⩾1MeV) slow down quasi-adiabatically with almost flat isolethargic energy distribution and reach the capture resonance energy of an element to be transmuted where they will have a high probability of being captured. Precision measurements of energy and space distributions of spallation neutrons (using 2.5 and 3.5 GeV/c protons) slowing down in a 3.3 m×3.3 m×3 m lead volume and of neutron capture rates on LLFFs 99Tc, 129I, and several other elements were performed. An appropriate formalism and appropriate computational tools necessary for the analysis and understanding of the data were developed and validated in detail. Our direct experimental observation of ARC demonstrates the possibility to destroy, in a parasitic mode, outside the Energy Amplifier core, large amounts of 99Tc or 129I at a rate exceeding the production rate, thereby making it practical to reduce correspondingly the existing stockpile of LLFFs. In addition, TARC opens up new possibilities for radioactive isotope production as an alternative to nuclear reactors, in particular for medical applications, as well as new possibilities for neutron research and industrial applications.

R. Adler a, T. Alhalel b A. Angelopoulos c, A. Apostolakis c, E. Aslanides d,b G. Backenstoss a, C.P. Bee d,e, j. Bennet e, J.K. Bienlein f, P. Bloch d, Ch. Bula g, G. Burgun h, p. Carlson i, J. Carvalho J, E. Cawley e, S. Charalambous k, M. Chardalas k, G. Chardin h, H. Cobbaert J, S. Dedoussis k, M. Dejardin h, j. Derre h, M. Dodgson e, J.C. Dousse ~, J. Duclos h, A. Ealet b, B. Eckart a, L. Faravel ~, P. Fassnacht b, J.L. Faure h, C. Felder a, R. Ferreira-Marques J, W. Fetscher f, M. Fidecaro d, A. Filip6i6 m, D. Francis h, J.R. Fry ~, C. Fuglesang i, E. Gabathuler e, R. Garnet d.~, D. Garreta h, T. Geralis b, H.-J. Gerber f, A. Go °, P. Gumplinger f.l, C. Guyot h, P.F. Harrison e,2, p.j. Hayman ~, W.G. Heyes d.3, R.W. Hollander o, K. Jansson i, H.U. Johner ~, K. Jon-And i, A. Kerek i, j. Kern ~, P.-R. Kettle g, C. Kochowski h, p. Kokkas P, R. Kreuger o, T. Lawry n, R. Le Gac q, E. Machado j,d, p. Maley ¢, N. Manthos P, G. Marel d.h, M. Miku~ m, j.p. Miller n, F. Montanet b, T. Nakada g, A. Onofre J, B. Pagels ", P. Pavlopoulos d.4, F. Pelucchi b, j. Pinto da Cunha J, A. Policarpo J, G. Polivka a, H. Postma o, R. Rickenbach a, B.L. Roberts n, E. Rozaki c, T. Ruf f, L. Sacks e, L. Sakeliou c, P. Sanders e, C. Santoni a, K. Sarigiannis c~4, M. Sch~ifer f, L. Schaller ~, A. Schopper d, P. Schune h, U. Seljak m, S. Szilagyi i, L. Tauscher a, C. Thibault q, F. Touchard q, C. Touramanis k, F. Triantis P, D.A. Troester a.5, E. Van Beveren J, M. Van den Putte o, C.W.E. Van Eijk o, G. Varner ", S. Vlachos ~, P. Weber f, C. Witzig f.6, C. Yeche h, D. Zavrtanik m and D. Zimmerman "

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 CP, T and CPT 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.

Using strangeness tagging at production time, CPLEAR measures time-dependent decay rate asymmetries between $K^0$ and $\bar{K}^0$, for picnic and semileptonic decays. Parameters describing CP, T, and CPT violation can be obtained with high precision. In the semileptonic channels neutral kaons are strangeness tagged also at the decay time, by the lepton charge, thus allowing the difference between the transition rates of $\bar{K}^0 \to K^0$ and $K^0 \to \bar{K}^0$ to be measured. In this way CPLEAR obtains the first direct measurement of T violation. By fitting the semileptonic rates under the constraint of the unitarity relation, we prove that in the reported measurement T violation is not mocked by CPT-violation effects in the decay amplitudes. Other CPLEAR measurements, only in part reported here, contribute to the experimental accuracy of the unitarity relation.

Using its unique capability of strangeness tagging at K-0 production in p (p) over bar --> K(-/+)pi K-+/-(0)(K-0) and at decay with the lepton charge in semileptonic decays, CPLEAR measured the semileptonic decay-rate asymmetryR(K-0 --> e(+) pi (-)nu) - R(K-0 --> e(-) pi (+)<()over bar>)/R(K-0 --> e(+)pi (-)nu) + R(K-0 --> e(-) pi (+<()over bar>))The asymmetry, fitted over the eigentime interval 1-20 tau (S), yielded a non-zero result of (6.6 +/- 1.3(stat) +/- 1.1syst) x 10(-3). A thorough phenomenological analysis identifies T violation in K-0 mixing and/or CPT violation in semileptonic decays as possible interpretations. A confrontation with world data on neutral kaon decays, however, excludes the latter with sufficient precision to establish the result as the first direct observation of time reversal non-invariance.

Neutral-kaon decays to pi e nu were analysed to determine the q(2) dependence of the K-e3(0), electroweak form factor f(+). Based on 365612 events, this form factor was found to have a linear dependence on q(2) with a slope lambda(+) = 0.0245 +/- 0.0012(stat) +/- 0.0022(syst). (C) 2000 Published by Elsevier Science B.V. All rights reserved.

A home-made, low cost, high speed, etched track detector measuring system, equipped with automatic track counting and classification procedures, was developed to measure and analyse quickly and accurately CR-39 etched track detectors used in indoor radon concentration surveys. The system provides increased detector throughput along with high measuring accuracy and it can therefore serve as a platform for the large scale measurements of the creek National Radon Survey that will take place in the near future. In this context, pilot measurements of indoor radiation were performed in selected Greek regions. Indoor radon concentrations were found in the range of 4 to 583 Bq.m(-3) with the highest levels observed near the water springs of Ikaria island. The indoor absorbed dose rate in air due to external irradiation from terrestrial sources was measured simultaneously, using thermoluminescence dosemeters (LiF TLD-100), and was found to be in the range of 19 to 107 nGy.h(-1) with an arithmetic mean value equal to 49 +/- 22 (1 sigma) nGy.h(-1), in good agreement with our previous study.

Data from the CPLEAR experiment, together with the most recent world averages for some of the neutral-kaon parameters, were constrained with the Bell-Steinberger (or unitarity) relation, allowing the T-violation parameter Re(epsilon) and the CPT-violation parameter Im(delta) of the neutral-kaon mixing matrix to be determined with an increased accuracy: Re(epsilon)=(164.9 +/- 2.5) x 10(-5), Im(delta)=(2.4 +/- 5.0) x 10(-5). Moreover, the constraint allows the CM-violation parameter for the neutral-kaon semileptonic decays, Re(), to be determined for the first time. The Delta S not equal Delta Q parameters Re(x_) and Im(x(+)) are given with an increased accuracy. The quantity Re(y + x_), which enters the T-violation CPLEAR asymmetry previously published, is determined to be (- 0.2 +/- 0.3) x 10(-3). The value obtained for Re(delta) is in agreement with the one resulting from a previous unconstrained fit and has a slightly smaller error. (C) 1999 Elsevier Science B.V, All rights reserved.

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

We test the Principle of Equivalence for particles and antiparticles, using CPLEAR data on tagged K0 and K0bar decays into pi^+ pi^-. For the first time, we search for possible annual, monthly and diurnal modulations of the observables |eta_+-| and phi_+-, that could be correlated with variations in astrophysical potentials. Within the accuracy of CPLEAR, the measured values of |eta_+-| and phi_+- are found not to be correlated with changes of the gravitational potential. We analyze data assuming effective scalar, vector and tensor interactions, and we conclude that the Principle of Equivalence between particles and antiparticles holds to a level of 6.5, 4.3 and 1.8 x 10^-9, respectively, for scalar, vector and tensor potentials originating from the Sun with a range much greater than the distance Earth-Sun. We also study energy-dependent effects that might arise from vector or tensor interactions. Finally, we compile upper limits on the gravitational coupling difference between K0 and K0bar as a function of the scalar, vector and tensor interaction range.

The CPT-violation parameters Re(delta) and Im(delta) determined recently by CPLEAR are used to evaluate the K-0-(K) over bar(0) mass and decay-width differences, as given by the difference between the diagonal elements of the neutral-kaon mixing matrix (M - i Gamma/2). The results - (M-K0K0 - M<(($)over bar>0 ($) over bar 0)) = (- 1.5 +/- 2.0) x 10(-18) GeV and (Gamma(K0K0) - Gamma(($) over bar 0 ($) over bar 0)) = (3.9 +/- 4.2) x 10(-18) GeV - are consistent with CPT invariance. The CPT invariance is also shown to hold within a few times 10(-3)-10(-4) for many of the amplitudes describing neutral-kaon decays to different final states. (C) 1999 Elsevier Science B.V. All rights reserved.

We study ππ correlations in the exclusive reaction \(\bar pp \to 2\pi ^ + 2\pi ^ - \pi ^0 \) at rest with complete reconstruction of the kinematics for each event. Inclusive and differential distributions properly normalized show an enhancement for small invariant masses M ++,M -- of like-pion pairs. An even stronger enhancement is seen for the double differential distributions for low pion-pair masses. The signal is strongest when the π0 energy is large and much weaker when this energy is small. Dynamical models with resonances in the final state are confronted with the data. For the kinematic situation where the ρ3π channel is important the simulation predicts a large pion correlation for the double differential density, qualitatively explaining the observed bahaviour. The stochastic HBT mechanism is not supported by these findings for the exclusive annihilation reaction studied.

We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of (K) over bar(0) transforming into K-0 and K-0 into (K) over bar(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 --> K (+/-) pi (+/-) K-0 ((K) over bar(0)) at rest, whereas the strangeness of the kaon at the decay time t = tau was tagged by the lepton charge in the final state. An average decay-rate asymmetry[R((K) over bart=00 --> e+pi-nut=tau) - R(Kt=00 --> e-pi+<(nu)over bar>t=tau)/R((K) over bart=00 --> e+pi-nut=tau) + R(Kt=00 --> e-pi+<(nu)over bar>t=tau)] = (6.6 +/- 1.3stat +/- 1.0syst) X 10-3was measured over the interval 1 tau(S) < tau < 20 tau(S), thus leading to evidence for time-reversal non-invariance. (C) 1998 Elsevier Science B.V. All righs reserved.