The structure of hadronic events fromZ0 decay is studied by measuring event shape variables, factorial moments, and the energy flow distribution. The distributions, after correction for detector effects and initial and final state radiation, are compared with the predictions of different QCD Monte Carlo programs with optimized parameter values. These Monte Carlo programs use either the second order matrix element or the parton shower evolution for the perturbative QCD calculations and use the string, the cluster, or the independent fragmentation model for hadronization. Both parton shower andO(α2s matrix element based models with string fragmentation describe the data well. The predictions of the model based on parton shower and cluster fragmentation are also in good agreement with the data. The model with independent fragmentation gives a poor description of the energy flow distribution. The predicted energy evolutions for the mean values of thrust, sphericity, aplanarity, and charge multiplicity are compared with the data measured at different center-of-mass energies. The parton shower based models with string or cluster fragmentation are found to describe the energy dependences well while the model based on theO(α2s calculation fails to reproduce the energy dependences of these mean values.
Unfolded Thrust distribution. Statistical error includes statistical uncertainties of the data as well as of the unfolding Monte Carlo Sample. The systematic error combines the uncertainties of measurements and of the unfolding procedure.
Unfolded Major distribution where Major is defined in the same way as Thrust but is maximized in a plane perpendicular to the Thrust axis.
Unfolded Minor distribution where the minor axis is defined to give an orthonormal system.
From the measured ratio of the invisible and the leptonic decay widths of theZ0, we determine the number of light neutrino species to beNv=3.05±0.10. We include our measurements of the forward-backward asymmetry for the leptonic channels in a fit to determine the vector and axial-vector neutral current coupling constants of charged leptons to theZ0. We obtain\(\bar g_V=- 0.046_{ - 0.012}^{ + 0.015}\) and\(\bar g_A=- 0.500 \pm 0.003\). In the framework of the Standard Model, we estimate the top quark mass to bemt=193−69+52±16 (Higgs) GeV, and we derive a value for the weak mixing angle of sin2θW=1−(MW/MZ)2=0.222 ± 0.008, corresponding to an effective weak mixing angle of\(\sin ^2 \bar \theta _W= 0.2315\pm0.0025\).
Additional systematic uncertainty of 0.4 pct.
Acceptance corrected cross section for cos(theta)<0.8 and for extrapolation to full solid angle. Additional systematic uncertainty of 0.8 pct.
Acceptance corrected cross section for cos(theta)<0.7 and for extrapolation to full solid angle. Additional systematic uncertainty of 2.1 pct.
We present a study of energy-energy correlations based on 83 000 hadronic Z 0 decays. From this data we determine the strong coupling constant α s to second order QCD: α s (91.2 GeV)=0.121±0.004(exp.)±0.002(hadr.) −0.006 +0.009 (scale)±0.006(theor.) from the energy-energy correlation and α s (91.2 GeV)=0.115±0.004(exp.) −0.004 +0.007 (hadr.) −0.000 +0.002 (scale) −0.005 +0.003 (theor.) from its asymmetry using a renormalization scale μ 1 =0.1 s . The first error (exp.) is the systematic experimental uncertainly, the statistical error is negligible. The other errors are due to hadronization (hadr.), renormalization scale (scale) uncertainties, and differences between the calculated second order corrections (theor.).
Statistical errors are equal to or less than 0.6 pct in each bin. There is also a 4 pct systematic uncertainty.
ALPHA_S from the EEC measurement.. The first error given is the experimental error which is mainly the overall systematic uncertainty: the first (DSYS) error is due to hadronization, the second to the renormalization scale, and the third differences between the calculated and second order corrections.
ALPHA_S from the AEEC measurement.. The first error given is the experimental error which is mainly the overall systematic uncertainty: the first (DSYS) error is due to hadronization, the second to the renormalization scale, and the third differences between the calculated and second order corrections.
We have measured the cross section for e + e − →hadrons over the center of mass energy range of the Z 0 peak, from 88.22 to 95.03 GeV. We determine the Z 0 mass M z =91.164±0.013 (experiment) ±0.030 (LEP) GeV. Within the framework of the standard model we determine the invisible width, Γ invisible =0.502±0.018 GeV, and the number of light neutrino species, N ν =3.01±0.11. We exclude the existence of a supersymmetric scalar neutrino having a mass less than 31.4 GeV, at the 95% confidence level. We performed a model independent combined fit to the e + e − →hadrons and e + e − → μ + μ − data to determine total width, leptonic width and hadronic width of the Z 0 .
Cross sections from 1990 data. Additional systematic error 1.5 pct.
Cross sections from 1989 data. This data has been rescaled by 0.96 from original publication PL B237 (90) 136. Additional systematic error 2.0 pct.
We present a study of jet multiplicities based on 37 000 hadronic Z 0 boson decays. From this data we determine the strong coupling constant α s =0.115±0.005 ( exp .) −0.010 +0.012 (theor.) to second order QCD at √ s =91.22GeV.
Errors are combined statistical and systematic uncertainties.
No description provided.
We have made a precise measurement of the cross section for e + e − →Z 0 →hadrons with the L3 detector at LEP, covering the s range from 88.28 to 95.04 GeV. From a fit to the Z 0 mass, total width, and the hadronic cross section to be M Z 0 =91.160 ± 0.024 (experiment) ±0.030(LEP) GeV, Γ Z 0 =2.539±0.054 GeV, and σ h ( M Z 0 )=29.5±0.7 nb. We also used the fit to the Z 0 peak cross section and the width todetermine Γ invisible =0.548±0.029 GeV, which corresponds to 3.29±0.17 species of light neutrinos. The possibility of four or more neutrino flavors is thus ruled out at the 4σ confidence level.
No description provided.
Total hadronic cross section.
We report the results of first physics runs of the L3 detector at LEP. Based on 2538 hadron events, we determined the mass m z 0 and the width Γ z 0 of the intermediate vector boson Z 0 to be m z 0 =91.132±0.057 GeV (not including the 46 MeV LEP machine energy uncertainty) and Γ z 0 =2.588±0.137 GeV. We also determined Γ invisible =0.567±0.080 GeV, corresponding to 3.42±0.48 number of neutrino flavors. We also measured the muon pair cross section and determined the branching ratio Γ μμ = Γ h =0.056±0.006. The partial width of Z 0 →e + e − is Γ ee =88±9±7 MeV.
No description provided.
Using the Mark-J detector at the high-energy e+e− collider PETRA, we compare the data from hadron production with the complete second-order QCD calculation over the energy region 22 to 46.78 GeV. We determine the QCD parameter Λ=100±30−45+60 MeV which yields the strong-coupling constant αs=0.12±0.02 for s=44 GeV.
No description provided.
Axis error includes +- 0.0/0.0 contribution (DUE TO FRAGMENTATION MODEL).
With use of the MARK-J detector at s=34.7 GeV 21 000 e+e−→hadron events have been collected. By measurement of the asymmetry in angular energy correlations the strong coupling constant αs=0.13±0.01 (statistical)±0.02 (systematic) is determined, in complete second order, and independent of the fragmentation models and QCD cutoff values used.
DATA REQUESTED FROM THE AUTHORS.
No description provided.
The strong interaction coupling constant α s has been measured with a new method, the planar triple energy correlation in the reaction e + e - → hadrons at center-of-mass energies ranging from 14 GeV to 46.78 GeV. A complete second-order perturbative QCD calculation was used. Λ MS = 110 ± 30 −55 +70 MeV is found.
No description provided.
No description provided.
No description provided.
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