Overall systematic error is 2.3 pct.
Overall systematic error is 2.6 pct.
Overall systematic error is 2.8 pct.
We report on the measurement of the leptonic and hadronic cross sections and leptonic forward-backward asymmetries at theZ peak with the L3 detector at LEP. The total luminosity of 40.8 pb−1 collected
Results from 1990 data. Additional systematic uncertainty of 0.3 pct.
Results from 1991 data. Additional systematic uncertainty of 0.15 pct.
Results from 1992 data. Additional systematic uncertainty of 0.15 pct.
The decays η → γγ and η ′ → ηπ + π − have been observed in hadronic decays of the Z produced at LEP. The fragmentation functions of both the η and η ′ have been measured. The measured multiplicities for x > 0.1 are 0.298±0.023±0.021 and 0.068±0.016 for η and η ′ respectively. While the fragmentation function for the η is fairly well described by the JETSET Monte Carlo, it is found that the production rate of the η ′ is a factor of four less than the corresponding prediction.
No description provided.
Additional 7 pct systematic error.
Additional 23 pct systematic error.
The search for an additional heavy gauge boson Z′ is described. The models considered are based on either a superstring-motivated E 6 or on a left-right symmetry and assume a minimal Higgs sector. Cross sections and asymmetries measured with the L3 detector in the vicinity of the Z resonance during the 1990 and 1991 running periods are used to determine limits on the Z-Z′ gauge boson mixing angle and on the Z′ mass. For Z′ masses above the direct limits, we obtain the following allowed ranges of the mixing angle, θ M at the 95% confidence level: −0.004 ⪕ θ M ⪕ 0.015 for the χ model, −0.003 ⪕ θ M ⪕ 0.020 for the ψ model, −0.029 ⪕ θ M ⪕ 0.010 for the η model, −0.002 ⪕ θ M ⪕ 0.020 for the LR model,
Data taken during 1990.
Data taken during 1991.
Data taken during 1990.
We report on the properties of theZ resonance from 62 500Z decays into fermion pairs collected with the ALEPH detector at LEP, the Large Electron-Positron storage ring at CERN. We findMZ=(91.193±0.016exp±0.030LEP) GeV, ΓZ=(2497±31) MeV, σhad0=(41.86±0.66)nb, and for the partial widths Γinv=(489±24) MeV, Γhad(1754±27) MeV, Γee=(85.0±1.6)MeV, Γμμ=(80.0±2.5) MeV, and Γττ=(81.3±2.5) MeV, all in good agreement with the Standard Model. Assuming lepton universality and using a lepton sample without distinction of the final state we measure Γu=(84.3±1.3) MeV. The forward-backward asymmetry in leptonic decays is used to determine the vector and axial-vector weak coupling constants of leptors,gv2(MZ2)=(0.12±0.12)×10−2 andgA2(MZ2)=0.2528±0.0040. The number of light neutrino species isNν=2.91±0.13; the electroweak mixing angle is sin2θW(MZ2)=0.2291±0.0040.
Hadronic cross section from the charged track selection trigger.
Hadronic cross section from the calorimeter selection trigger.
Averaged hadronic cross section.
We present a study of the inclusive ω and η′ production based on 3.1 million hadronic Z decays recorded with the L3 detector at LEP during 1991–1994. The production rates per hadronic Z decay have been measured to be 1.17±0.17 ω mesons and 0.25±0.04 η′ mesons. The production rates and the differential cross sections have been compared with predictions of the JETSET and the HERWIG Monte Carlo models. We have observed that the differential cross sections can be described by an analytical quantum chromodynamics calculation.
Final production rates per hadronic Z0 decay.
Corrected production rates from the omega --> pi+ pi- p0 decay mode. Extrapolation to full x range.
Corrected production rates from the etaprime --> pi+ pi- eta decay mode. Extrapolation to full x range.
This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -> ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.
Measured cross sections and forward-backward asymmetries for non-radiative E+ E- --> E+ E- events.
Differential cross sections for non-radiative E+ E- --> E+ E- events at centre of mass energy 189 GeV.
Differential cross sections for non-radiative E+ E- --> E+ E- events at centre of mass energy 192 GeV.
We report on measurements of e + e − annihilation into hadrons and lepton pairs. The data have been taken with the L3 detector at LEP at center-of-mass energies between 161 GeV and 172 GeV. In a data sample corresponding to 21.2 pb −1 of integrated luminosity 2728 hadronic and 868 lepton-pair events are selected. The measured cross sections and leptonic forward-backward asymmetries agree well with the Standard Model predictions.
No description provided.
No description provided.
No description provided.
We have performed a high-statistics measurement of Bhabha scattering and of the production of hadrons in electron-positron annihilation at PETRA energies (12 GeV<~s<~36.7 GeV). Combining the results with measurements of μ+μ− and τ+τ− production enables us to compare our results with electroweak theory. We find sin2θw=0.27±0.08. This is in good agreement with the value obtained from neutrino experiments which were carried out in entirely different kinematic regions.
ASYMMETRY WAS USED.
OVERALL FIT USED.
No description provided.
Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its flavour independence, tests of the SU(3) gauge structure of QCD, study of coherence effects, and measurements of single-particle inclusive distributions and two-particle correlations for many identified baryons and mesons.
Charged particle sphericity distribution.
Charged particle aplanarity distribution.
Charged particle Thrust distribution.
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