The Curvature of F_2^p(x, Q^2) as a Probe of Perturbative QCD Evolutions in the small-x Region

TL;DR

This paper investigates the behavior of the proton structure function F_2^p at very small x using NLO and NNLO perturbative QCD, showing good agreement with experimental data and highlighting positive curvature as a key test of QCD validity.

Contribution

It demonstrates that perturbative QCD predictions for F_2^p at small x are stable across schemes and match recent measurements, emphasizing curvature as a perturbative test.

Findings

Perturbative QCD accurately describes F_2^p at small x.

F_2^p exhibits positive curvature increasing with decreasing x.

Predictions are scheme-independent and match experimental data.

Abstract

Perturbative NLO and NNLO QCD evolutions of parton distributions are studied, in particular in the (very) small-x region, where they are in very good agreement with all recent precision measurements of F_2^p(x,Q^2). These predictions turn out to be also rather insensitive to the specific choice of the factorization scheme (MS or DIS). A characteristic feature of perturbative QCD evolutions is a positive curvature of F_2^p which increases as x decreases. This perturbatively stable prediction provides a sensitive test of the range of validity of perturbative QCD.