Extraction of $\alpha_s$ from deep inelastic scattering at large $x$

TL;DR

This paper analyzes the effective strong coupling constant in QCD by extracting it from high-x deep inelastic scattering data, revealing a smooth transition between perturbative and nonperturbative regimes and explaining parton-hadron duality.

Contribution

It introduces a unified approach to describe the running coupling at low scales by extracting it from experimental data, bridging perturbative and nonperturbative QCD.

Findings

Effective coupling exhibits freezing at low scales.

Parton-hadron duality can be explained with nonperturbative effects.

Smooth transition from perturbative to nonperturbative QCD observed.

Abstract

We present an analysis of the role of the running coupling constant at the intersection of perturbative and nonperturbative QCD. Although the approaches that have been considered so far in these two regimes appear to be complementary to each other, a unified description might derive through the definition of the effective coupling, as they both provide ways of analyzing its freezing at low values of the scale. We extract the effective coupling from all available experimental data on the unpolarized structure function of the proton, $F_2^p$, at large values of Bjorken $x$, including the resonance region. We suggest that parton-hadron duality observed in this region can be explained if nonperturbative effects are included in the coupling constant. The outcome of our analysis is a smooth transition from perturbative to nonperturbative QCD physics, embodied in the running of the coupling constant at intermediate scales.