Process-independent effective coupling. From QCD Green's functions to phenomenology

TL;DR

This paper introduces a process-independent QCD effective charge derived from Green's functions, compares it to a process-dependent charge, and applies it to proton form factor calculations, offering a new approach to QCD phenomenology.

Contribution

It proposes a novel, process-independent QCD effective charge based on Green's functions, utilizing the pinch technique and background field method, and demonstrates its application to proton form factors.

Findings

Effective charge closely matches the process-dependent Bjorken sum rule charge.

The effective charge provides a consistent framework for QCD phenomenology.

Application to proton form factors shows promising results.

Abstract

This article reports on a very recent proposal for a new type of process-independent QCD effective charge [Phys.Rev.D96(2017)054026] defined, as an anologue of the Gell-Mann-Low effective charge in QCD, on the ground of nothing but the knowledge of the gauge-field two-point Green's function, albeit modified within a particular computational framework; namely, the combination of pinch technique and background field method which makes possible a systematic rearranging of classes of diagrams in order to redefine the Green's function and have them obey linear QED-like Slavnov-Taylor identities. We have here calculated that effective charge, shown how strikingly well it compares to a process-dependent effective charge based on the Bjorken sum rule; and, finally, employed it in an exploratory calculation of the proton electromagnetic form factor in the hard scattering regime.