49 research outputs found

    Assessing the Forecasting Performance of a Macroeconomic Model

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    This paper contains a description of a small quarterly forecasting model for the Finnish economy. We evaluate the forecasting properties of the model by means of stochastic simulation involving both the endogenous and exogenous variables of the model. The simulations allow us to identify and quantify the main sources of forecasting uncertainty. We are also able to assess the linearity of the model. Forecasting performance is also analyzed in a conventional way by means of dynamic simulation. The important issue in these simulations is the stability of the model: how simulated values depend on the estimation period and the ordering of time periods.forecasting; macro models; simulation

    A PRECISE MEASUREMENT OF THE Z RESONANCE PARAMETERS THROUGH ITS HADRONIC DECAYS

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    A measurement of the cross section for e+e-→ hadrons using 11 000 hadronic decays of the Z boson at ten different center-of-mass energies is presented. A three-parameter fit gives the following values for the Z mass MZ, the total width ΓZ, the product of the electronic and hadronic partial widths ΓeΓh, and the unfolded pole cross section σ0: MZ = 91.171 ± 0.030 (stat.) ± 0.030 (beam) GeV, ΓZ = 2.511 ± 0.065 GeV, ΓeΓh = 0.148 ± 0.006 (stat.) ± 0.004 (syst.) GeV2, σ0 = 41.6 ± 0.7 (stat.) ± 1.1 (syst.) nb, Good agreement with the predictions of the standard model is observed. From a two-parameter fit the number of massless neutrino generations is found to be Nv = 2.91 ± 0.26. Thus the hypothesis of a fourth neutrino with mass less than 40 GeV is excluded with 95% confidence level. Combining the cross section measurements with the ratio Γl/Γh reported in another DELPHI paper [Phys. Lett. B 241 (1990) 425], the hadronic, leptonic and invisible widths are found to be Γh = 1741 ± 61 MeV, Γl = 85.1 ± 2.9 MeV, Γh/Γl = 20.45 ± 0.98, Γinv = 515 ± 54 MeV, in good agreement with the standard model.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

    Experimental study of the triple gluon vertex

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    In four-jet events from e+e-→Z0→multihadrons one can separate the three principal contributions from the triple-gluon vertex, double gluon-bremsstrahlung and the secondary quark-antiquark production, using the shape of the two-dimensional angular distributions in the generalized Nachtmann-Reiter angle 0NR* and the opening angle of the secondary jets. Thus one can identify directly the contribution from the triple-gluon vertex without comparison with a specific non-QCD model. Applying this new method to events taken with the DELPHI-detector we get for the ratio of the colour factor NC to the fermionic Casimir operator CF: NC/C F=2.55±0.55(stat.)±0.4(fragm.+models)±0.2(error in bias) in agreement with the value 2.25 expected in QCD from NC=3 and CF=4/3.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

    Study of the leptonic decays of the ZO Boson

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    Measurements are presented of the cross section ratios Rℓ = σℓ(e+e-→ℓ+ℓ -)/σhh(e+e-→hadrons) for ℓ = e, μ and τ using data taken from a scan around the Z0. The results are Re = (5.09±0.32±0.18)%, Rμ = (4.96±0.35±0.17)% and Rτ,=(4.72±0.38± 0.29)% where, for the ratio Re, the t-channel contribution has been subtracted. These results are consistent with the hypothesis of lepton universality and test this hypothesis at the energy scale s ∼ 8300 GeV2. The absolute cross sections σℓ(e+e-→ℓ +ℓ-) have also been measured. From the cross sections the leptonic partial widths Γe = (83.2±3.0±2.4) MeV, (ΓeΓμ) 1/2=(84.6±3.0±2.4) MeV and (ΓeΓτ) 1/2=(82.6±3.3±3.2) MeV have been extracted. Assuming lepton universality the ratio Γℓ/Γh=(4.89±0.20± 0.12) × 10-2 was obtained, together with Γℓ=(83.6±1.8±2.2) MeV. The number of light neutrino species is determined to be Nv=3.12±0.24±0.25. Al the data are consistent with the predictions of the standard model.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

    A Search for neutral Higgs particles in Z0 decays

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    Contains fulltext : 129376.pdf (Publisher’s version ) (Open Access

    Study of final state photons in hadronic Z0 decay and limits on new phenomena

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    The differential cross section for final state radiation from primary quarks is obtained from a study of isolated energetic photons produced in the reaction e+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 the Z0, the observed rate determines the electroweak coupling constants of up and down type quarks, i.e. {Mathematical expression} No evidence is seen for additional photon production from anomalous decays of the Z0 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 reaction e+e-→Z0→H +γ, H→hadrons, (b) an excited quark, q*→q+γ, and (c) the contribution of an anomalous decay of the Z0 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* or Z*) varies from 10 GeV/c2 to 80 GeV/c2. © 1992 Springer-Verlag0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

    SEARCH FOR THE t AND b-prime QUARKS IN HADRONIC DECAYS OF THE Z0 BOSON

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    We present a search for the third generation up type quark t and a possible fourth down type quark b' in hadronic Z0 decays observed in DELPHI at the LEP collider. For any scenario with a decay through the charged current or into a charged Higgs with a mass at least 6 GeV/c2 below the t and 3 GeVc2 below the b' mass, we set a lower limit for the t quark mass at 44.0 GeV/c2 and for the b' mass at 44.5 GeV/c2. For specific scenarios the mass limits are slightly higher, e.g. for charged current decays the limits are 44.5 and 45.0 GeV/c2 respectively, where all limits are given at a 95% confidence level. © 1990.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

    A Study of intermittency in hadronic Z0 decays

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    The correlations in rapidity in hadron production from e+e- annihilation near the Z0 resonance were studied by means of the method of factorial moments, using data taken with the DELPHI detector at LEP. The parton shower hadronization model was found to be in quantitative agreement with the data, in contrast with previous results at lower energies. © 1990.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

    The DELPHI detector at LEP

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    DELPHI is a 4π detector with emphasis on particle identification, three-dimensional information, high granularity and precise vertex determination. The design criteria, the construction of the detector and the performance during the first year of operation at the large electron positron collider (LEP) at CERN are described.0info:eu-repo/semantics/publishe

    Charged particle multiplicity distributions in Z0 hadronic decays

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    This paper presents an analysis of the multiplicity distributions of charged particles produced in Z0 hadronic decays in the DELPHI detector. It is based on a sample of 25364 events. The average multiplicity is =20.71±0.04(stat)±0.77(syst) and the dispersion D=6.28±0.03(stat)±0.43(syst). The data are compared with the results at lower energies and with the predictions of phenomenological models. The Lund parton shower model describes the data reasonably well. The multiplicity distributions show approximate KNO-scaling. They also show positive forward-backward correlations that are strongest in the central region of rapidity and for particles of opposite charge. © 1991 Springer-Verlag.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe
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