S. Bethke

Experimental tests of asymptotic freedom

Abstract Quantum chromodynamics (QCD), the gauge field theory of strong interaction, has specific features, asymptotic freedom and confinement, which determine the behaviour of quarks and gluons in particle reactions at high and low energy scales. QCD predicts that the strong coupling strength α s decreases with increasing energy or momentum transfer, and vanishes at asymptotically high energies. In this review, the history and status of experimental tests of asymptotic freedom are summarized. The world summary of measurements of α s is updated, leading to an unambiguous verification of the running of α s and of asymptotic freedom, in excellent agreement with the predictions of QCD. Averaging a set of measurements balanced between different particle processes and the available energy range, results in a new and improved world average of α s ( M Z 0 ) = 0.1189 ± 0.0010 .

αs at Zinnowitz 2004

A review of measurements of

Determination of ±s from a differential-jet-multiplicity distribution in e+e- collisions at ss =29 and 91 GeV

\alpha_s

World Summary of αS (2012)

is given, representing the status of April 2004. The results prove the energy dependence of

Determination of the Strong Coupling \boldmath{\as} from hadronic Event Shapes and NNLO QCD predictions using JADE Data

\alpha_s

Determination of the strong coupling αS from hadronic event shapes with \mathcal{O}(\ensuremath {\alpha _{\mathrm {S}}}^{3}) and resummed QCD predictions using JADE data

and are in excellent agreement with the expectations of Quantum Chromodynamics, QCD. Evolving all results to the rest energy of the

Tests of power corrections for event shapes in e+ e- annihilation

Z^0

A measurement of the QCD colour factors using event shape distributions at \(\sqrt{s}=14\) to 189 GeV

boson, the world average of

QCD studies at LEP

\alpha_s(M_Z)

Determination of the strong coupling constant

is determined from measurements which are based on QCD calculations in complete NNLO perturbation theory, giving