Non-singlet quark helicity PDFs of the nucleon from pseudo-distributions

• Published in: The journal of high energy physics Vol. 2023; no. 3; pp. 86 - 51
• Main Authors: 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
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 14.03.2023; Springer Nature B.V; SpringerOpen
• Subjects: Amplitudes; Classical and Quantum Gravitation; Collaboration; Computation; Contamination; Distillation; Distribution functions; Elementary Particles; Hadronic Spectroscopy; Helicity; High energy physics; Lattice QCD; Lattice Quantum Field Theory; Nucleons; Parton Distributions; Partons; Physics; Physics and Astronomy; Polynomials; Quantum chromodynamics; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quarks; Regular Article - Theoretical Physics; Relativity Theory; String Theory; Structure and Interactions; Systematic errors; Lattice QCD; Lattice Quantum Field Theory; Structure and Interactions; Hadronic Spectroscopy; Parton Distributions
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP03(2023)086

A bstract 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 z 2 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 z 2 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 μ 2 . The leading-twist helicity PDFs as well as several sources of systematic error, including higher-twist effects, discretization errors, and the aforementioned z 2 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.