Journal of High Energy Physics
The non-singlet helicity quark parton distribution functions (PDFs) of the nucleon are determined from lattice QCD, by jointly leveraging pseudo-distributions and the distillation spatial smearing paradigm. A Lorentz decomposition of appropriately isolated space-like matrix elements reveals pseudo-distributions that contain information on the leading-twist helicity PDFs, as well as an invariant amplitude that induces an additional z2 contamination of the leading-twist signal. An analysis of the short-distance behavior of the space-like matrix elements using matching coefficients computed to next-to-leading order (NLO) exposes the desired PDF up to this additional z2 contamination. Due to the non-conservation of the axial current, we elect to isolate the helicity PDFs normalized by the nucleon axial charge at the same scale μ2. The leading-twist helicity PDFs as well as several sources of systematic error, including higher-twist effects, discretization errors, and the aforementioned z2 contaminating amplitude are jointly determined by characterizing the computed pseudo-distribution in a basis of Jacobi polynomials. The Akaike Information Criterion is exploited to effectively average over distinct model parameterizations and cuts on the pseudo-distribution. Encouraging agreement is observed with recent global analyses of each non-singlet quark helicity PDF, notably a rather small non-singlet anti-quark helicity PDF for all quark momentum fractions.
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Original Publication Citation
Edwards, R., Egerer, C., Karpie, J., Karthik, N., Monahan, C., Morris, W., Orginos, K., Radyushkin, A., Richards, D., & Romero, E. (2023). Non-singlet quark helicity PDFs of the nucleon from pseudo-distributions. Journal of High Energy Physics, 2023(3), 1-51, Article 86. https://doi.org/10.1007/JHEP03(2023)086
Edwards, Robert; Egerer, Colin; Karpie, Joseph; Karthik, Nikhil; Monahan, Christopher; Morris, Wayne; Orginos, Kostas; Radyushkin, Anatoly; Richards, David; Romero, Eloy; Sufian, Raza Sabbir; Zafeiropoulos, Savvas; and On behalf of the HadStruc collaboration, "Non-Singlet Quark Helicity PDFs of the Nucleon From Pseudo-Distributions" (2023). Physics Faculty Publications. 785.