Comparison of e+e− annihilation with QCD and determination of the strong coupling constant

doi:10.1016/0370-2693(80)90914-4

Physics Letters B

Volume 94, Issue 3, 11 August 1980, Pages 437-443

https://doi.org/10.1016/0370-2693(80)90914-4 Get rights and content

Abstract

We have analyzed 1113 events of the reaction e⁺e⁻ → hadrons at CM energies of 12 and 30 GeV in order to make a detailed comparison with QCD. Perturbative effects can be well separated from effects depending on the quark and gluon fragmentation parameters to yield a reliable measurement of the coupling constant α_S. At 30 GeV, the result is α_S = 0.17 ± 0.02 (statistical) ± 0.03 (systematic). QCD model predictions, using the fragmentation parameters determined along with α_S, agree with both gross properties of the final states and with detailed features of the three-jet states.

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Cited by (62)

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A simple cluster model for limited-p_t jets is developed. The formalism combines a string model description of color screening in non-perturbative QCD and an accurate parameterization of hadron production from low-mass clusters. The non-perturbative description of soft color evolution is found to provide a substantial improvement on present, purely perturbative QCD-cluster models. An extended model including hard perturbative QCD radiation is also presented. Results of this composite model are found to be in good agreement with experimental results for e⁺e⁻ annihilation over the entire energy range 3 GeV ⩽ E_CM ⩽ 35 GeV. Shortcomings in the present formalism are examined and specific suggestions for further improvements are made.
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Reconstruction of charged D^∗'s produced inclusively in e⁺e−. annihilation at CM energies near 34.4 GeV is accomplished in the decay modes $D ∗^{+} → D^{0} π^{+} → K^{−} gp^{+} π^{0} π^{+} and D ∗^{+} → D^{0} π^{+} → K^{−} gp^{+} π^{−} π^{+} π^{+}$ and their charge conjugates. Using these and previously reported $D ∗^{+} → D^{0} π^{+} → K^{−} gp^{+} π^{+} and D ∗^{+} → D^{0} π^{+} → K^{−} gp^{+} π^{+} + missing π^{0}$ channels we present evidence for hard gluon bremsstrahlung from charm quarks and show that the ratio of the quark-gluon coupling constant of charm quarks to the coupling constant obtained in the average hadronic event, $α_{s}^{c} α_{rms} = 100 ± 0.20 ± 1.20$ . Our result provides evidence that the quark-gluon coupling constant is independent of flavor.
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⁷: Supported by the Deutsches Bundesministerium für Forschung und Technologie.

⁵: Now at SLAC, Stanford, CA, USA.

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Physics Letters B

Abstract

References (19)

Phys. Rev. Lett.

DESY Report 79/80

Phys. Lett.

DESY Report 79/86

Phys. Rev.

Phys. Lett.

Phys. Lett.

Cited by (62)

Determinations of the QCD strong coupling α<inf>s</inf> and the scale Λ<inf>QCD</inf>

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A summary of experimental results from Mark J: High energy e<sup>+</sup>e<sup>-</sup> collisions at PETRA

e<sup>+</sup>e<sup>-</sup> physics at petra-the first five years

Experimental test of the flavor independence of the quark-gluon coupling constant

Semihard processes in QCD