$α_s$ 2002

TL;DR

This paper updates measurements of the strong coupling constant $α_s$ using data from deep inelastic scattering, $e^+e^-$ annihilation, hadron collisions, and lattice QCD, highlighting NNLO calculations and four-loop running. It confirms the energy dependence of $α_s$ in agreement with QCD and derives a new world average $\overline{α_s}(M_Z) = 0.1183 \pm 0.0027$ by combining NNLO results with optimized correlations, also reporting $\Lambda_{\overline{MS}}$ values for $N_f=3,4,5$. The analysis discusses challenges in averaging non-Gaussian theoretical uncertainties and stresses the importance of correlation-aware methods. Collectively, the work strengthens confidence in the running of $α_s$ and establishes a precise benchmark at the $Z$ mass.

Abstract

An update of measurements of the strong coupling constant $α_s$ is given, representing the status of September 2002. The results convincingly prove the energy dependence of $α_s$ 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 $α_s(M_Z)$ is determined from measurements which are based on QCD calculations in complete NNLO perturbation theory, giving $$ α_s(M_Z) = 0.1183 \pm 0.0027 . $$

Figures (2)

• Figure 1: Summary of measurements of $\alpha_{\rm s} (Q^2 )$. Results which are based on fits of $\alpha_{\rm s}(M_{\rm Z})$ to data in $ranges$ of $Q$, assuming the QCD running of $\alpha_{\rm s}$, are not shown here but are included in the overall summary of $\alpha_{\rm s}(M_{\rm Z})$, see Fig. 2 and Tab. 1 .
• Figure 2: Summary of measurements of $\alpha_{\rm s}(M_{\rm Z})$. Filled symbols represent results based on complete NNLO QCD calculations .