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First simultaneous global QCD analysis of kaon and pion parton distributions with lattice QCD constraints

P. C. Barry1, Chueng-Ryong Ji2, W. Melnitchouk3, N. Sato3, and Fernanda Steffens4,5 (JAM Collaboration—Pion PDF Analysis Group)

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Phys. Rev. D 114, 014057 – Published 27 July, 2026

DOI: https://doi.org/10.1103/ny6w-1n19

Abstract

We perform the first simultaneous global QCD analysis of pion and kaon parton distribution functions (PDFs) constrained by pion- and kaon-induced Drell-Yan (DY) and leading neutron electroproduction data together with lattice QCD data on pion and kaon PDF moments. The analysis indicates a softer valence u¯ distribution in the K− than in the π− and a significantly more peaked valence s-quark density in K− compared with the u¯. The effective exponent governing the high-x behavior of the PDF is found to be larger for u¯ in the kaon, βu¯K−=1.6(2), than in the pion, βu¯π−=1.16(4), in the range 0.7≤x≤0.95. From the gluon momentum fractions, we find the pion’s gluon content accounts for ≈1/3 of the mass budget of the pion at μ=2  GeV, but only ≈1/4 for the kaon.

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Phys. Rev. D 114, 014057– Published 27 July, 2026
  • Received 27 October 2025
  • Accepted 22 June 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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