Gluon mass and freezing of the QCD coupling

TL;DR

This paper derives gauge-invariant, infrared-finite solutions for the gluon propagator in QCD, revealing a dynamical gluon mass that causes the strong coupling to freeze at low energies, indicating an infrared fixed point.

Contribution

It presents a novel gauge-invariant approach to solving the Schwinger-Dyson equation, showing the gluon mass drops asymptotically and leads to a frozen coupling in QCD.

Findings

Gluon propagator solutions are infrared finite and fit by a massive propagator.

The effective gluon mass decreases as inverse square of momentum transfer.

The strong coupling freezes at a finite value in the infrared.

Abstract

Infrared finite solutions for the gluon propagator of pure QCD are obtained from the gauge-invariant non-linear Schwinger-Dyson equation formulated in the Feynman gauge of the background field method. These solutions may be fitted using a massive propagator, with the special characteristic that the effective mass employed drops asymptotically as the inverse square of the momentum transfer, in agreement with general operator-product expansion arguments. Due to the presence of the dynamical gluon mass the strong effective charge extracted from these solutions freezes at a finite value, giving rise to an infrared fixed point for QCD.