Determination of the Strong Coupling Constant by the ALPHA Collaboration

TL;DR

This paper presents a high-precision determination of the strong coupling constant at the Z-mass scale using lattice QCD simulations and innovative renormalization schemes, bridging low-energy experimental data with high-energy perturbative results.

Contribution

It introduces a novel renormalization scheme based on an improved gradient flow for non-perturbative scale dependence analysis in lattice QCD.

Findings

Consistent determination of the strong coupling constant at the Z-mass scale.

Agreement with world averages by FLAG and PDG.

Validation of the novel gradient flow scheme at low and intermediate energies.

Abstract

A high precision determination of the strong coupling constant in the MS-bar scheme at the Z-mass scale, using low energy quantities, namely pion/kaon decay constants and masses, as experimental input is presented. The computation employs two different massless finite volume renormalization schemes to non-perturbatively trace the scale dependence of the respective running couplings from a scale of about 200 MeV to 100 GeV. At the largest energies perturbation theory is reliable. At high energies the Schroedinger-Functional scheme is used, while the running at low and intermediate energies is computed in a novel renormalization scheme based on an improved gradient flow. Large volume Nf=2+1 QCD simulations by CLS are used to set the overall scale. The result is compared to world averages by FLAG and the PDG.