Concerning pion parton distributions

Abstract

Analyses of the pion valence-quark distribution function (DF), $u^{\pi }(x;\zeta )$, which explicitly incorporate the behaviour of the pion wave function prescribed by quantum chromodynamics (QCD), predict $u^{\pi }(x\simeq 1;\zeta )\sim (1-x{)}^{\beta (\zeta )}$, $\beta (\zeta \gtrsim m_p)>2$, where $m_p$ is the proton mass. Nevertheless, more than forty years after the first experiment to collect data suitable for extracting the $x\simeq 1$ behaviour of $u^{\pi }$, the empirical status remains uncertain because some methods used to fit existing data return a result for $u^{\pi }$ that violates this constraint. Such disagreement entails one of the following conclusions: the analysis concerned is incomplete; not all data being considered are a true expression of qualities intrinsic to the pion; or QCD, as it is currently understood, is not the theory of strong interactions. New, precise data are necessary before a final conclusion is possible. In developing these positions, we exploit a single proposition, viz. there is an effective charge which defines an evolution scheme for parton DFs that is all-orders exact. This proposition has numerous corollaries, which can be used to test the character of any DF, whether fitted or calculated.

arXiv comment15 pages, 9 figures, 1 table

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• QCD Running Couplings and Effective Charges
• Emergent Hadron Mass in Strong Dynamics
• Emergence of pion parton distributions
• Proton and pion distribution functions in counterpoint
• The valence quark, sea, and gluon content of the pion from the parton distribution functions and the electromagnetic form factor
• Parton distributions of light quarks and antiquarks in the proton
• Pseudo-scalar mesons: light front wave functions, GPDs and PDFs
• Dynamical mass generation in Minkowski space at QCD scale
• Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab
• Empirical Determination of the Pion Mass Distribution
• Contact interaction analysis of octet baryon axialvector and pseudoscalar form factors
• Origin of the Proton Mass
• Polarised parton distribution functions and proton spin
• Hadron Structure using Continuum Schwinger Function Methods
• Fixed-target charmonium production and pion parton distributions
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• Pseudoscalar Meson Parton Distributions Within Gauge-Invariant Nonlocal Chiral Quark Model
• Parton Distribution Functions for Pseudoscalar Mesons in the COnfining Effective Chiral Quark Theory
• Searching for $a_0(980)$-meson parton distribution function
• Feasibility Study of Pion and Kaon Structure via the Sullivan Process at EicC