Showing papers by "Claude Leroy published in 1991"
TL;DR: In this article, the authors show the context of analysis and the first results of a research on media temporalities of the elderly, showing that the global relation of the autonomous elderly persons to the media can evolve when confronted to their new temporal framework and the new program offer, whereas their representations and use of the media remain quite stable.
146 citations
TL;DR: In this article, an improved measurement of the mass of the Z0 boson, its total width and its partial decay widths into hadrons and leptons, as well as the effective axial vector and vector couplings to charge lepton was presented.
Abstract: We report on an improved measurement of the mass of theZ0 boson, its total width and its partial decay widths into hadrons and leptons, as well as the effective axial vector and vector couplings to charged leptons. These measurements are based on a data set of approximately 160 000 hadronicZ0 decays and 18 000 decays into electrons, muons and taus, recorded by the OPAL experiment at centre of mass energies near the mass of theZ0. The total width and the partial widths to visible final states, derived from the measured cross sections, are used to extract the invisible width. The effective couplings of theZ0 to charged leptons are studied using measurements of the lepton pair cross sections and forward-backward asymmetries at the different centre of mass energy points of theZ0 scan. The implications of our results in the context of the Standard Model are discussed.
66 citations
TL;DR: In this paper, Bose-Einstein correlations between like-sign charged track pairs have been studied in e + e − annihilation hadronic events at centre-of-mass energies around the Z 0 peak as a function of Q, the four-momentum difference of the pair.
63 citations
TL;DR: In this article, the average τ polarization at the Z° resonance is measured to be −0.22 ± 0.04 and a value for the weak mixing angle of sin 2 θ W = 0.07.
58 citations
TL;DR: In this article, a symmetry under transposition of the energies and directions of a quark and gluon jet was selected for e+e−three-jet events at LEP using lepton tagging of quark jets through observation of semi-leptonic charm and bottom quark decays.
48 citations
TL;DR: In this paper, the authors investigated the production of K0 mesons in e+e− interactions at center of mass energies in the region of the Z0 mass with the OPAL detector at LEP.
45 citations
TL;DR: In this paper, the authors measured the fraction of events containing semi-leptonic decays of b flavoured hadrons using the shape of the momentum and transverse momentum distributions of the muon candidates.
40 citations
TL;DR: In this article, the authors used the semi-leptonic decays of charm and bottom quarks to identify quarks and gluons in 3-jet events from hadronic Z0 decays.
36 citations
33 citations
TL;DR: In this paper, a factorial moment analysis has been performed on the differential multiplicity distributions of hadronic final states of the Z 0 recorded with the OPAL detector at LEP.
29 citations
TL;DR: In this article, an investigation of the production of D ∗ ± mesons produced in e + e − collisions at energies around the Z 0 pole is presented, and the properties of D∗ mesons generated in the reaction Z 0 → c c c are studied.
TL;DR: In this paper, the production rate of final state photons in hadronic Z0 decays is measured as a function of ycut = Mij2/Ecm2 the jet resolution parameter and minimum mass of the photon-jet system.
TL;DR: In this paper, the authors measured the photon yield in lepton pair events recorded by the OPAL detector in a data sample corresponding to an integrated luminosity of 7.1 pb−1 at centre-of-mass energies between 88 GeV and 94 GeV.
TL;DR: In this paper, a sample of approximately 45 reconstructed J ψ mesons was measured to be Br(Z0→J/ψ + X) = (4.5±0.8± 0.6) × 10−3, where the first error is statistical, the second systematic, and the third error is due to the uncertainty in the leptonic decay rate of the Jψ.
01 Mar 1991-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a detailed study of neutron irradiated n-type silicon detectors was carried out including leakage current measurements after first and second irradiation, annealing procedures optimization, deep level transient spectroscopy (DLTS), and thermally stimulated currents (TSC) analyses of the produced defects in the bulk of the detectors.
Abstract: A detailed study of neutron irradiated n-type silicon detectors was carried out including leakage current measurements after first and second irradiation, annealing procedures optimization, deep level transient spectroscopy (DLTS), and thermally stimulated currents (TSC) analyses of the produced defects in the bulk of the detectors.
TL;DR: In this paper, the OPAL detector at LEP is used to measure the branching ratio of the Z0 into invisible particles by measuring the cross section of single photon events ine+e− collisions at centre-of-mass energies near theZ0 resonance.
Abstract: The OPAL detector at LEP is used to measure the branching ratio of theZ0 into invisible particles by measuring the cross section of single photon events ine+e− collisions at centre-of-mass energies near theZ0 resonance. In a data sample of 5.3 pb−1, we observe 73 events with single photons depositing more than 1.5 GeV in the electromagnetic calorimeter, with an expected background of 8±2 events not associated with invisibleZ0 decay. With this data we determine theZ0 invisible width to be 0.50±0.07±0.03 GeV, where the first error is statistical and the second systematic. This corresponds to 3.0±0.4±0.2 light neutrino generations in the Standard Model.
01 Jul 1991
TL;DR: In this article, the compensation condition (e/ π = 1) for the silicon calorimeters used at the next generation of hadronic colliders (LHC, UNK, SSC) is discussed.
Abstract: The compensation condition (e/ π = 1) is discussed. It mainly determines the performances of the silicon calorimeters to be used at the next generation of hadronic colliders (LHC, UNK, SSC).
01 Jul 1991
TL;DR: In this paper, a thorough study of lateral shower profiles has been undertaken to improve the precision of the measurement of the absolute electromagnetic response, and the main features of the local hardening effect as a function of the thickness of low-Z material were explained by a 1/E distribution of ionizing particles inside the shower, while those of the lateral profile are explained by an exponential radial distribution.
Abstract: In silicon sampling calorimeters, a local hardening effect occurs when inserting a small thickness of low-Z material next to the thin active layer. This effects, which modifies appreciably the electromagnetic response, allows the control of the relative responses to hadronic and electromagnetic showers. A thorough study of lateral shower profiles has been undertaken to improve the precision of the measurement of the absolute electromagnetic response. The main features of the local hardening effect as a function of the thickness of low-Z material are explained by a 1/E distribution of ionizing particles inside the shower, while those of the lateral profile are explained by an exponential radial distribution.
01 Jul 1991
TL;DR: In this paper, a fast monolithic preamplifier was employed at hadron calorimeters for noise as a function of the expected leakage current in an SSC/LCH silicon calorimeter.
Abstract: For experiments with future hadron colliders involving multi-TeV proton beams, such as the LHC and SSC, sampling calorimeters with silicon as active medium satisfy the special experimental conditions. Defect formation processes and electrical behavior of neutron irradiated p + -n ion implanted silicon detectors were studied. A fast monolithic preamplifier to be employed at hadron calorimeters was investigated for noise as a function of the expected leakage current in an SSC/LCH silicon calorimeter.
TL;DR: In this article, three jet variables constructed from multi-hadronic events produced by Z0 decays are compared to theoretical calculations assuming a vector gluon or a hypothetical scalar gluons.
Abstract: Three-jet variables constructed from multi-hadronic events produced byZ0 decays are compared to theoretical calculations assuming a vector gluon or a hypothetical scalar gluon. The data yield conclusive direct evidence for the former case. The distributions of the reduced energy of the second-most energetic jet and of the cosine of the Ellis-Karliner angle are chosen to demonstrate this effect.
TL;DR: In this article, a combination of low-Z and high-Z materials for the absorber allows the reduction of the calorimeter response to the electromagnetic component of the incoming hadronic showers (the local hardening effect).
Abstract: In an Si/U hadron calorimeter, using a combination of low-Z and high-Z materials for the absorber allows the reduction of the calorimeter response to the electromagnetic component of the incoming hadronic showers (the local hardening effect). As a result, a ratio varying from e/ pi >1 to e/ pi >
02 Nov 1991
TL;DR: In this article, a combination of low-Z and high-Z materials as absorbers enables the transformation of the electron energy distribution of the incident showers in two media with different critical energies via the filtering effect.
Abstract: In a calorimeter with silicon readout, the use of a combination of low-Z (Fe) and high-Z (Pb) materials as absorbers enables the transformation of the electron energy distribution of the incident showers in two media with different critical energies via the filtering effect. As a result, the electromagnetic energy and consequently the e/MIP ratio value can be substantially reduced as a function of the thickness of high-Z (Pb) material present in the absorber, making it possible to tune the e/ pi ratio and making possible the achievement of the compensation condition e/ pi =1. >