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Global QCD Analysis of Pion Parton Distributions with Threshold Resummation
P C Barry1, Chueng-Ryong Ji2, N Sato1
1Jefferson Lab, Newport News, Virginia 23606, USA.
Physical Review Letters
|December 22, 2021
Summary
This study presents the first global Quantum Chromodynamics (QCD) analysis of pion parton distributions. Resummation effects significantly alter quark and gluon momentum, boosting gluon contribution to pion mass.
Area of Science:
- High Energy Physics
- Quantum Chromodynamics (QCD)
- Particle Physics
Background:
- Understanding the internal structure of pions is crucial in particle physics.
- Previous analyses lacked comprehensive treatments of resummation effects.
- Drell-Yan cross sections provide key data for probing parton distributions.
Purpose of the Study:
- To perform the first global Quantum Chromodynamics (QCD) analysis of pion valence, sea quark, and gluon distributions.
- To investigate the impact of threshold resummation on these distributions.
- To determine the momentum fraction carried by gluons and their contribution to pion mass.
Main Methods:
- Bayesian Monte Carlo framework for global QCD analysis.
- Inclusion of threshold resummation at next-to-leading log accuracy.
- Analysis of Drell-Yan cross section data.
Main Results:
- The large-x asymptotics of the valence quark distribution show significant variation, with βv ranging from ≈1 to >2.5.
- Threshold resummation redistributes momentum between quarks and gluons.
- Gluons carry approximately 40% of the pion's momentum.
Conclusions:
- Resummation effects are critical for accurately describing pion parton distributions.
- The gluon contribution to the pion mass is estimated to be around 40 MeV.
- This analysis provides essential insights into the non-perturbative structure of pions.
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