First results on the running coupling in QCD with two massless flavours

TL;DR

This paper presents the first non-perturbative calculation of the running coupling in two-flavour QCD using the Schrödinger functional scheme, highlighting the importance of non-perturbative methods for accurate Lambda-parameter estimation.

Contribution

It provides the initial non-perturbative results for the running coupling in two-flavour QCD within the Schrödinger functional scheme, connecting high-energy and low-energy scales.

Findings

Non-perturbative evolution of the coupling is crucial for accurate Lambda-parameter estimation.

The study establishes a framework for relating the Lambda-parameter to low-energy observables.

Results demonstrate the necessity of non-perturbative methods in QCD coupling calculations.

Abstract

We report on the non-perturbative computation of the running coupling of two-flavour QCD in the Schr"odinger functional scheme. The corresponding Lambda-parameter, which describes the coupling strength at high energy, is related to a low energy scale which still remains to be connected to a hadronic ``experimentally'' observable quantity. We find the non-perturbative evolution of the coupling indispensable to avoid untolerable errors in the estimated Lambda-parameter.