The Strong Coupling Constant from Hadron Structure Phenomenology

TL;DR

This paper explores the behavior of the strong coupling constant across different energy scales in QCD, highlighting experimental evidence for a smooth transition and proposing methods to extract an effective coupling from scattering data.

Contribution

It introduces an approach to extract an effective coupling constant from experimental data, bridging perturbative and nonperturbative QCD regimes.

Findings

Experimental data shows a smooth transition of the coupling constant across scales.

Effective coupling constant can be extracted from electron-proton scattering data.

Proposes a method to match nonperturbative models with perturbative QCD.

Abstract

We present recent developments on the role of the running coupling constant at the intersection of perturbative and nonperturbative QCD. A number of experiments show a smooth transition from small to large scales given by the four-momentum transfer in the reactions. This is at variance with perturbative QCD where the running coupling constant becomes infinite when the scale equals $\Lambda_{{\tiny QCD}}$. Approaches using an effective coupling constant could help interpret the opposite trend of data as compared to standard perturbative QCD predictions. We give an overview of the role of the coupling constant in the procedure to match nonperturbative hadronic model to perturbative QCD and we propose an extraction of an effective coupling constant from inclusive electron proton scattering data at large Bjorken x.