$α_s$ at Zinnowitz 2004

TL;DR

α_s is reviewed with status up to April 2004, confirming its energy-scale dependence in agreement with QCD. The paper compiles results from DIS, e+e− annihilation, and hadron colliders, emphasizing NNLO calculations and a careful world-average methodology. A world average of α_s(M_Z) = 0.1182 ± 0.0027 is reported, with Λ_MS̄ values provided for different flavor counts, illustrating consistency across processes. The findings reinforce the QCD prediction for the running of α_s and deliver a precise global value for future phenomenology.

Abstract

A review of measurements of $α_s$ is given, representing the status of April 2004. The results 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 world average of $α_s(M_Z)$ is determined from measurements which are based on QCD calculations in complete NNLO perturbation theory, giving $α_s(M_Z) = 0.1182 \pm 0.0027 .$

Figures (4)

• Figure 1: $\alpha_{\rm s} (E^{jet}_T )$ values determined from QCD fits of the measured $d \sigma \over dE^{jet}_T$ from ZEUS zeus03. The solid line corresponds to the central value of $\alpha_{\rm s}(M_{\rm Z^0})$ determined in zeus03, the dashed line represents the world average as2002.
• Figure 2: Summary of measurements of $\alpha_{\rm s} (Q^2 )$ from electroweak precision measurements (filled symbols; in NNLO QCD) and from jet and event shape observables (open symbols; in resummed NLO QCD) in ${\rm e^+\rm e^-}$ annihilation. The dashed curves represent the world average of $\alpha_{\rm s}(M_{\rm Z^0})$lepqcd04.
• Figure 3: Summary of measurements of $\alpha_{\rm s} (Q^2 )$. Results which are based on fits of $\alpha_{\rm s}(M_{\rm Z^0})$ 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 $\alpha_{\rm s}(M_{\rm Z^0})$, see Figure 4 and Table 1.
• Figure 4: Summary of measurements of $\alpha_{\rm s}(M_{\rm Z^0})$. Filled symbols represent results based on complete NNLO QCD calculations.