${\alpha }_s$ 2002

Abstract

An update of measurements of the strong coupling constant ${\alpha }_s$ is given, representing the status of September 2002. The results convincingly prove the energy dependence of ${\alpha }_s$ and are in excellent agreement with the expectations of Quantum Chromodynamics, QCD. Evolving all results to the rest energy of the $Z^0$ boson, the new world average of ${\alpha }_s(M_Z)$ is determined from measurements which are based on QCD calculations in complete NNLO perturbation theory, giving $${\alpha }_s(M_Z)=0.1183\pm \mathrm{0.0027.}$$

Comments: Talk presented at the QCD 02 High-Energy Physics International Conference in Quantum Chromodynamics, Montpellier (France), July 2-9, 2002; 8 pages, 2 figures