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Melnitchouk, W. [Jefferson Lab] (ORCID:0000000295215973)

Publications and source records attributed to Melnitchouk, W. [Jefferson Lab] (ORCID:0000000295215973).

2 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

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

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 Β― distribution in the K βˆ’ than in the Ο€ βˆ’ and a significantly more peaked valence s -quark density in K βˆ’ compared with the u Β― . The effective exponent governing the high- x behavior of the PDF is found to be larger for u Β― in the kaon, Ξ² u Β― K βˆ’ = 1.6 ( 2 ) , than in the pion, Ξ² u Β― Ο€ βˆ’ = 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 β‰ˆ 1 / 3 of the mass budget of the pion at ΞΌ = 2 GeV , but only β‰ˆ 1 / 4 for the kaon.

Barry, P. C. [Argonne National Laboratory] (ORCID:β†—
DOE OSTI2025

First study of polarized proton-proton scattering with small-π‘₯ helicity evolution

We perform a phenomenological study of helicity-dependent parton distribution functions (PDFs) using small-π‘₯ helicity evolution equations, incorporating for the first time single-inclusive jet production data in polarized proton-proton (𝑝⁒𝑝) scattering at parton momentum fractions π‘₯ <0.1. We also simultaneously include double-longitudinal spin asymmetries in inclusive and semi-inclusive deep-inelastic scattering probing π‘₯ <0.1. Employing the polarized small-π‘₯ pure-glue calculation of 𝑝⁒𝑝 β†’ 𝑔⁑𝑋 for the jet production cross section, we modify the large-𝑁 𝑐 &𝑁 𝑓 KPS-CTT evolution equations by setting 𝑁 𝑓 = 0 to replicate the large-𝑁𝑐 (pure-glue) limit, while retaining external quark flavors for the spinor field operators. We find that the 𝑝⁒𝑝 data have a considerable impact on the helicity PDFs at small π‘₯, reducing their uncertainties and leading to a total quark and gluon helicity in the proton for π‘₯ < 0.1 of βˆ’0.04 Β±0.23. Combining our analysis with a recent JAM helicity PDF analysis of the world polarized data, which includes π‘₯ > 0.1, we find a total quark and gluon helicity contribution for π‘₯ >10 βˆ’7 of between 0.02 and 0.51.

Adamiak, Daniel [Michigan State University] (ORCID↗