World Summary of $\alpha_s$ (2012)

TL;DR

This paper summarizes various measurements of the strong coupling constant, $oldsymbol{ ext{α}_s}$, and provides a new world average value at the Z boson mass scale, consolidating results from multiple experimental and theoretical methods.

Contribution

It introduces a new method of pre-averaging results within classes of measurements to determine a precise world average of $oldsymbol{ ext{α}_s}$ at $oldsymbol{M_Z}$ scale, updating the 2009 value.

Findings

The world average of $oldsymbol{ ext{α}_s(M_Z)}$ is 0.1184 ± 0.0007.

The value of $oldsymbol{ ext{α}_s(M_Z)}$ remains unchanged since 2009.

Multiple measurement methods are combined for a comprehensive summary.

Abstract

Determinations of the strong coupling strength, $\alpha_s$, are summarised and a new world average value of $\alpha_s (M_Z)$ is determined, using a new method of pre-averaging results within classes of measurements like hadronic $\tau$ decays, deep inelastic scattering processes, lattice calculations, electron-positron annihilation processes and electro-weak precision fits. The overall result is $$\alpha_s (M_Z) = 0.1184 \pm 0.0007,$$ unchanged from the value obtained in 2009. This presentation is an excerpt from the QCD review section of the 2012 Review of Particle Physics (RPP) of the Particle Data Group.