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

Understand

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.