Global QCD Analysis of Pion Parton Distributions with Threshold Resummation

TL;DR

This paper presents the first comprehensive global QCD analysis of pion parton distributions incorporating threshold resummation, revealing significant effects on the large-x behavior and gluon momentum share.

Contribution

It introduces a Bayesian Monte Carlo framework with threshold resummation for pion PDFs, exploring different resummation treatments and their impact on parton distributions.

Findings

Large-x valence quark behavior varies significantly with resummation method.

Gluons carry about 40% of the pion's momentum after resummation effects.

Resummation redistributes momentum, increasing gluon contribution to pion mass.

Abstract

We perform the first global QCD analysis of pion valence, sea quark, and gluon distributions within a Bayesian Monte Carlo framework with threshold resummation on Drell-Yan cross sections at next-to-leading log accuracy. Exploring various treatments of resummation, we find that the large-$x$ asymptotics of the valence quark distribution $\sim (1-x)^{\beta_v}$ can differ significantly, with $\beta_v$ ranging from $\approx 1$ to $> 2.5$ at the input scale. Regardless of the specific implementation, however, the resummation induced redistribution of the momentum between valence quarks and gluons boosts the total momentum carried by gluons to $\approx 40\%$, increasing the gluon contribution to the pion mass to $\approx 40$ MeV.