Symmetry Constraints on Pion Valence Structure

TL;DR

This paper demonstrates that the pion valence quark distribution function, constrained by the pion's electromagnetic form factor, aligns with QCD expectations and exhibits a convex shape with a specific large-x power law.

Contribution

It establishes a connection between the pion's electromagnetic form factor and its valence quark distribution using QCD effective charges and generalized parton distributions, providing new insights into the pion structure.

Findings

Pion electromagnetic form factor is well approximated by a monopole.

The valence quark distribution is convex at large x.

The large-x behavior matches QCD predictions.

Abstract

The profile of the pion valence quark distribution function (DF) remains controversial. Working from the concepts of QCD effective charges and generalised parton distributions, we show that since the pion elastic electromagnetic form factor is well approximated by a monopole, then, at large light-front momentum fraction, the pion valence quark DF is a convex function described by a large-$x$ power law that is practically consistent with expectations based on quantum chromodynamics.