Lattice-motivated holomorphic nearly perturbative QCD

TL;DR

This paper develops a new holomorphic QCD coupling model consistent with lattice results, perturbative behavior, and tau decay data, improving the precision of low-momentum QCD predictions.

Contribution

It introduces a lattice-motivated, holomorphic QCD coupling that matches low- and high-momentum behaviors and accurately reproduces tau decay observables.

Findings

The new coupling goes to zero at low momenta, aligning with lattice results.

It accurately reproduces the tau decay rate and spectral functions.

It yields more precise estimates of gluon and higher-twist condensates.

Abstract

Newer lattice results indicate that, in the Landau gauge at low spacelike momenta, the gluon propagator and the ghost dressing function are finite nonzero. This leads to a definition of the QCD running coupling, in a specific scheme, that goes to zero at low spacelike momenta. We construct a running coupling which fulfills these conditions, and at the same time reproduces to a high precision the perturbative behavior at high momenta. The coupling is constructed in such a way that it reflects qualitatively correctly the holomorphic (analytic) behavior of spacelike observables in the complex plane of the squared momenta, as dictated by the general principles of Quantum Field Theories. Further, we require the coupling to reproduce correctly the nonstrange semihadronic decay rate of tau lepton which is the best measured low-momentum QCD observable with small higher-twist effects. Subsequent application of the Borel sum rules to the V+A spectral functions of tau lepton decays, as measured by OPAL Collaboration, determines the values of the gluon condensate and of the V+A 6-dimensional condensate, and reproduces the data to a significantly higher precision than the usual MSbar running coupling.