Drawing insights from pion parton distributions

TL;DR

This paper uses a continuum approach to calculate the pion's valence, glue, and sea quark distributions, aligning with QCD predictions and lattice QCD results, providing insights into pion structure and guiding future experiments.

Contribution

It introduces a symmetry-preserving continuum method to unify pion parton distributions with form factors, matching lattice QCD results after evolution.

Findings

Valence quark momentum fraction: 0.48(3)

Glue momentum fraction: 0.41(2)

Sea momentum fraction: 0.11(2)

Abstract

A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale $\zeta_2:=2\,$GeV: $\langle x_{\rm valence} \rangle = 0.48(3)$, $\langle x_{\rm glue} \rangle = 0.41(2)$, $\langle x_{\rm sea} \rangle = 0.11(2)$; and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, ${q}^\pi(x)$, exhibits the $x\simeq 1$ behaviour predicted by quantum chromodynamics (QCD). After evolution to $\zeta=5.2\,$GeV, the prediction for ${q}^\pi(x)$ matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.