Schachter, M.J.
DSIGMA/DCHI
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A Measurement of energy correlations and a determination of alpha-s (M2 (Z0)) in e+ e- annihilations at s**(1/2) = 91-GeV

The OPAL collaboration Akrawy, M.Z. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 252 (1990) 159-169, 1990.
Inspire Record 298707 DOI 10.17182/hepdata.29525

From an analysis of multi-hadron events from Z 0 decays, values of the strong coupling constant α s ( M 2 Z 0 )=0.131±0.006 (exp)±0.002(theor.) and α s ( M z 0 2 ) = −0.009 +0.007 (exp.) −0.002 +0.006 (theor.) are derived from the energy-energy correlation distribution and its asymmetry, respectively, assuming the QCD renormalization scale μ = M Z 0 . The theoretical error accounts for differences between O ( α 2 s ) calculations. A two parameter fit Λ MS and the renormalization scale μ leads to Λ MS =216±85 MeV and μ 2 s =0.027±0.013 or to α s ( M 2 Z 0 )=0.117 +0.006 −0.008 (exp.) for the energy-energy correlation distribution. The energy-energy correlation asymmetry distribution is insensitive to a scale change: thus the α s value quoted above for this variable includes the theoretical uncertainty associated with the renormalization scale.

3 data tables
Table 1

Data are at the hadron level, unfolded for initial-state radiation and for detector acceptance and resolution. Note that the systematic errors between bins are correlated.

Table 2

Alpha-s determined from the EEC measurements. The systematic error is an error in the theory.

Table 3

Alpha-s determined from the AEEC measurements. The systematic error is an error in the theory.


Energy-energy correlations in hadronic final states from Z0 decays

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adami, F. ; et al.
Phys.Lett.B 252 (1990) 149-158, 1990.
Inspire Record 300161 DOI 10.17182/hepdata.29534

We have studied the energy-energy angular correlations in hadronic final states from Z 0 decay using the DELPHI detector at LEP. From a comparison with Monte Carlo calculations based on the exact second order QCD matrix element and string fragmentation we find that Λ (5) MS =104 +25 -20 ( stat. ) +25 -20( syst. ) +30 00 ) theor. ) . MeV, which corresponds to α s (91 GeV)=0.106±0.003(stat.)±0.003(syst.) +0.003 -0.000 (theor). The theoretical error stems from different choices for the renormalization scale of α s . In the Monte Carlo simulation the scale of α s as well as the fragmentation parameters have been optimized to described reasonably well all aspects of multihadron production.

2 data tables
Table 1

Data requested from the authors.

Table 2

Values of LAMBDA-MSBAR(5) and ALPHA-S(91 GeV) deduced from the EEC measurements. The second systematic error is from the theory.