Showing papers by "Manolis Dris published in 1992"
TL;DR: In this article, the Bose-Einstein correlation between pairs of like-sign charged particles produced in e + e − annihilations near the Z 0 peak has been studied using data taken with the DELPHI detector at LEP.
73 citations
01 Dec 1992-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The Barrel Ring Imaging CHerenkov (BRICH) detector as mentioned in this paper is a photoensitive gas-filled drift chamber where the photoelectrons drift to a MWPC of special construction.
Abstract: A short explanation is given of the Barrel Ring Imaging CHerenkov (BRICH) detector and its performance. We discuss in brief some of the requirements to run this detector. Special attention is paid to the functioning of the Cherenkov photon detector — a photosensitive gas-filled drift chamber where the photoelectrons drift to a MWPC of special construction. We illustrate the BRICH performance with some preliminary results.
61 citations
TL;DR: A classifier based on a feed-forward neural network has been used for separating a sample of about 123 500 selected hadronic decays of the Z0, collected by DELPHI during 1991, into three classes according to the flavour of the original quark pair.
44 citations
TL;DR: In this paper, an analysis of the production of strange particles from the decays of the Z 0 boson into multihadronic final states is presented based on about 90 000 selected hadronic Z 0 decays collected by the DELPHI detector at LEP in 1990.
42 citations
TL;DR: In this paper, seven unambiguous events out of a sample of 270 000 Z0 decays, contain in the same jet a Ds meson and a muon at large transverse momentum relative to the jet axis.
36 citations
TL;DR: In this paper, the weak mixing angle has been measured from the charge asymmetry of hadronic events with two different approaches using the DELPHI detector at LEP, both methods are based on a momentum-weighted charge sum to determine the jet charge in both event hemispheres.
31 citations
TL;DR: In this paper, the strong coupling constant αs is derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions, based on second order perturbation theory and using two hadronization corrections, one computed with a parton shower model and the other with a QCD matrix element model.
Abstract: Distributions of event shape variables obtained from 120600 hadronicZ decays measured with the DELPHI detector are compared to the predictions of QCD based event generators Values of the strong coupling constant αs are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions The final result, αs(M
Z), is based on second order perturbation theory and uses two hadronization corrections, one computed with a parton shower model and the other with a QCD matrix element model
29 citations
TL;DR: In this article, the search in DELPHI data for neutral Higgs bosons is described, and no candidate for the Standard Model Higgs is seen in Z0 decays to H 0 ν ν, H 0 μ + μ − or H 0τ+τ− after selections that proved efficient for finding simulated H0.
29 citations
TL;DR: In this article, the authors measured the final state radiation from primary quarks in the DELPHI detector at the CERN LEP collider and obtained upper limits on the production cross section times branching fraction of the Higgs boson in the reaction.
Abstract: The differential cross section for final state radiation from primary quarks is obtained from a study of isolated energetic photons produced in the reactione+e−→Z0→hadrons+γ, as measured in the DELPHI detector at the CERN LEP collider. When combined with the measurement of the total hadronic width of theZ0, the observed rate determines the electroweak coupling constants of up and down type quarks, i.e.,
$$v_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-
ulldelimiterspace} 3}}^2 + a_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-
ulldelimiterspace} 3}}^2 = 1.13 \pm 0.29 and v_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-
ulldelimiterspace} 3}}^2 + a_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-
ulldelimiterspace} 3}}^2 = 1.65 \pm 043.$$
No evidence is seen for additional photon production from anomalous decays of theZ0 or from decays of new particles. This measurement leads to upper limits on the production cross section times branching fraction of (a) the Higgs boson in the reactione+e−→Z0→H +γ,H→hadrons, (b) an excited quark,q*→q+γ, and (c) the contribution of an anomalous decay of theZ0 into a photon and hadrons. These limits, all at the 95% confidence level, vary from 3 to 10pb as the mass of the intermediate state (H,q* orZ*) varies from 10 GeV/c2 to 80 GeV/c2.
22 citations
TL;DR: In this paper, the authors search for possible fourth family heavy neutrinos, pair produced in Z0 decays, in a sample of about 112 000 hadronic Z0 final states collected with the DELPHI detector.
22 citations
TL;DR: In this article, the authors used the spectra of prompt electrons and muons from the semi-leptonic decays of heavy hadrons produced in Z 0 decays to measure the coupling of the Z 0 -turb quarks weighted by the B hadrons mean semi leptonic branching fraction.
Abstract: The spectra of prompt electrons and muons from the semi-leptonic decays of heavy hadrons produced inZ
0 decays have been used to measure the coupling of theZ
0 tob quarks weighted by theB hadrons mean semi-leptonic branching fraction, giving a value:
$$BR_{sl}^b *{{\Gamma _{b\bar b} } \mathord{\left/ {\vphantom {{\Gamma _{b\bar b} } {\Gamma _H }}} \right. \kern-
ulldelimiterspace} {\Gamma _H }} = 0.0221 \pm 0.0015$$
. The data has also been used to measure the value of the fragmentation parameter, defined in the context of the LUND PS Model, version 7.2, giving:
$$\varepsilon (b) = \left( {8\begin{array}{*{20}c} { + 5} \\ { - 3} \\ \end{array} \pm 2} \right)10^{ - 3} $$
. The corresponding value of the mean fraction of the beam energy taken by aB hadron in the fragmentation of ab quark is:
$$\overline {X_E^b } = 0.69\begin{array}{*{20}c} { + 0.02} \\ { - 0.03} \\ \end{array} \pm 0.01$$
. If the values of
$$\Gamma _{b\bar b} $$
andΓ
H
are taken from the Standard Model, the following value is obtained for the mean semi-leptonic braching fraction ofB hadrons: BR
sl
=(10.1±0.7)%. Taking the value of
$${{\Gamma _{b\bar b} } \mathord{\left/ {\vphantom {{\Gamma _{b\bar b} } {\Gamma _{\rm H} }}} \right. \kern-
ulldelimiterspace} {\Gamma _{\rm H} }}$$
from an independent analysis of DELPHI data based on the use of the boosted sphericity product, a value: BR
sl
=(10.1±1.3)% is obtained.
TL;DR: In this paper, the orientation of three-jet events from e + e − → Z 0 → multi-hadrons is studied, in particular the polar angle distributions of the thrust axis and of the normal to the threejet plane, and the azimuthal correlations between the hadron plane and the one defined by the beam and thrust axes.
TL;DR: In this article, a search was performed for the production of excited charged leptons decaying into an ordinary lepton and one photon, and the pair production of lepton-photon particles of mass below 45 GeV/c2 was excluded.
Abstract: Using a data sample of 115000 hadronicZ
0 decays, a search was performed for the production of excited charged leptons decaying into an ordinary lepton and one photon. Pair production of excited leptons of mass below 45 GeV/c2 is excluded. From an analysis of the lepton-photon mass spectra this experiment is also able to exclude single production of these particles for masses that reach up to 85 GeV/c2, if the compositeness scale is below 1 TeV.
TL;DR: In this article, a strong increase of the mean transverse momentum with the number of charged particles nch is observed in e+e- annihilations into hadrons at LEP energies.