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Proton’s Isovector Parton Distribution Function with Updated Analysis of Large-Momentum Lattice Data

Xiangdong Ji1 and Yushan Su2,*

  • *Contact author: ysu12345@umd.edu
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Phys. Rev. Lett. 137, 161901 – Published 14 October, 2026

DOI: https://doi.org/10.1103/8ytm-zbf4

Abstract

The proton’s unpolarized u(x)−d(x) parton distribution function (PDF) has been studied by a number of lattice QCD groups through large momentum expansion. However, due to lattice artifacts (excited state contaminations, unphysical pion masses, and discretization effects) and less-advanced theoretical analysis (renormalizations, large-distance extrapolations, and large-log resummations), the resulting PDFs cannot be compared strictly with experimental data. By using the state-of-the-art theoretical tools and mitigating the lattice artifacts empirically, we reanalyze the available datasets in the literature and find that the new PDF for the physical-limit-extrapolated dataset (MSULat20) is consistent with global fits within ∼1σ, while others are broadly compatible. This provides evidence that large momentum expansion is capable of accurately predicting the x dependence of the PDFs when ideal lattice data become available.

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Phys. Rev. Lett. 137, 161901– Published 14 October, 2026
  • Received 2 July 2026
  • Revised 27 August 2026
  • Accepted 22 September 2026
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