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A Global determination of alpha-s (M(z0)) at LEP

The OPAL collaboration Acton, P.D. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 55 (1992) 1-24, 1992.
Inspire Record 333079 DOI 10.17182/hepdata.14606

The value of the strong coupling constant,$$\alpha _s (M_{Z^0 } )$$, is determined from a study of 15 d

16 data tables
Table 1

Differential jet mass distribution for the heavier jet using method T. The data are corrected for the finite acceptance and resolution of the detector and for initial state photon radiation.

Table 2

Differential jet mass distribution for the jet mass difference using methodT. The data are corrected for the finite acceptance and resolution of the detec tor and for initial state photon radiation.

Table 3

Differential jet mass distribution for the heavier jet using method M. The data are corrected for the finite acceptance and resolution of the detector and for initial state photon radiation.

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Measurement of the longitudinal cross-section using the direction of the thrust axis in hadronic events at LEP.

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Alexander, G. ; et al.
Phys.Lett.B 440 (1998) 393-402, 1998.
Inspire Record 474666 DOI 10.17182/hepdata.49354

In the process e+e- to hadrons, one of the effects of gluon emission is to modify the 1+cos(theta)**2 form of the angular distribution of the thrust axis, an effect which may be quantified by the longitudinal cross-section. Using the OPAL detector at LEP, we have determined the longitudinal to total cross-section ratio to be 0.0127+-0.0016+-0.0013 at the parton level, in good agreement with the expectation of QCD computed to Order(alpha_s**2) Comparisions at the hadron level with Monte Carlo models are presented. The dependence of the longitudinal cross-section on the value of thrust has also been studied, and provides a new test of QCD.

2 data tables
Table 1

Values of SIG(C=L) integrated over all Thrust.

Table 2

Measured values of the differential cross section, and the corresponding ratio of longitudinal to total cross sections, corrected to the hadron level.


rivet Analysis
Measurement of event shape distributions and moments in e+ e- --> hadrons at 91-GeV - 209-GeV and a determination of alpha(s).

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Eur.Phys.J.C 40 (2005) 287-316, 2005.
Inspire Record 669402 DOI 10.17182/hepdata.48652

We have studied hadronic events from e+e- annihilation data at centre-of-mass energies from 91 to 209 GeV. We present distributions of event shape observables and their moments at each energy and compare with QCD Monte Carlo models. From the event shape distributions we extract the strong coupling alpha_s and test its evolution with energy scale. The results are consistent with the running of alpha_s expected from QCD. Combining all data, the value of alpha_s(M_Z) is determined to be alpha_s(M_Z) = 0.1191 +- 0.0005 (stat.) +- 0.0010 (expt.) +- 0.0011 (hadr.) +- 0.0044 (theo.). The energy evolution of the moments is also used to determine a value of alpha_s with slightly larger errors: alpha_s(M_Z) = 0.1223 +- 0.0005 (stat.) +- 0.0014 (expt.) +- 0.0016 (hadr.) +0.0054 -0.0036 (theo.).

27 data tables
Table 1

Measured normalized differential distribution for 1-THRUST.

Table 2

Measured normalized differential distribution for HEAVY-JET-MASS.

Table 3

Measured normalized differential distribution for C-PARAMETER.

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