Hughlock, B.W.
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A Study of Jet Production Rates and a Test of QCD on the Z0 Resonance

The OPAL collaboration Akrawy, M.Z. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 235 (1990) 389-398, 1990.
Inspire Record 283783 DOI 10.17182/hepdata.29753

Relative production rates of multijet hadronic final states of Z 0 boson decays, observed in e + e − annihilation around 91 GeV centre of mass energy, are presented. The data can be well described by analytic O( α s 2 ) QCD calculations and by QCD shower model calaculations with parameters as determined at lower energies. A first judgement of Λ MS and of the renormalization scale μ 2 in O( α s 2 ) QCD results in values similar to those obtained in the continuum of e + e − annihilations. Significant scaling violations are observed when the 3-jet fractions are compared to the corresponding results from smaller centre of mass energies. They can be interpreted as being entirely due tot the energy dependence of α s , as proposed by the nonabelian nature of QCD, The possibility of an energy independent coupling constant can be excluded with a significance of 5.7 standard deviations.

1 data table
Table 1

Data are corrected for final acceptance and resolution of the detector. No explicit corrections for hadronisation effects are applied.


Measurement of the Z0 Mass and Width with the OPAL Detector at LEP

The OPAL collaboration Akrawy, M.Z. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 231 (1989) 530-538, 1989.
Inspire Record 282821 DOI 10.17182/hepdata.29757

We report an experimental determination of the cross section for e + e − → hadrons from a scan around the Z 0 pole. On the basis of 4350 hadronic events collected over seven energy points between 89.26 GeV and 93.26 GeV we obtain a mass of m z =91.01±0.05±0.05 GeV, and a total decay width of Γ z =2.60±0.13 GeV. In the context of the standard model t these results imply 3.1 ± 0.4 neutrino generations.

1 data table
Table 1

No description provided.


Determination of the Number of Light Neutrino Species

The ALEPH collaboration Decamp, D. ; Deschizeaux, B. ; Lees, J.P. ; et al.
Phys.Lett.B 231 (1989) 519-529, 1989.
Inspire Record 282904 DOI 10.17182/hepdata.29758

The cross-section for e + e − → hadrons in the vicinity of the Z boson peak has been measured with the ALEPH detector at the CERN Large Electron Positron collider, LEP. Measurements of the Z mass, M z = (91.174±0.070) GeV, the Z width Γ z =(2.68±0.15) GeV, and of the peak hadronic cross-section, σ had peak =(29.3±1.2) nb, are presented. With the constraints of the standard electroweak model, the number of light neutrino species is found to be N v =3.27±0.30. this results rules out of the possibility of a fourth type of light neutrino at 98% CL.

2 data tables
Table 1

Selection from TPC tracks.

Table 2

Selection by calorimeters.