Non-singlet quark helicity $$\mathrm{PDF}$$s of the nucleon from pseudo-distributions

Journal Article · 13 March 2023 · Journal of High Energy Physics (Online)

DOI: https://doi.org/10.1007/jhep03(2023)086 · OSTI ID:1962984

Edwards, Robert ^[1]; Egerer, Colin ^[1]; Karpie, Joseph ^[1]; Karthik, Nikhil ^[2]; Monahan, Christopher ^[3]; Morris, Wayne ^[4]; Orginos, Kostas ^[3]; Radyushkin, Anatoly ^[5]; Richards, David ^[1]; Romero, Eloy ^[1]; Sufian, Raza Sabbir ^[3]; Zafeiropoulos, Savvas ^[2]

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1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2. College of William and Mary, Williamsburg, VA (United States)
3. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States)
4. Old Dominion University, Norfolk, VA (United States)
5. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion University, Norfolk, VA (United States)

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.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP); National Science Foundation (NSF); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR); USDOE National Nuclear Security Administration (NNSA)
• Contributing Organization: HadStruc Collaboration
• Grant/Contract Number: AC05-06OR23177; SC0011941; FG02-04ER41302; FG02-97ER41028; SC0023047; AC02-05CH11231; AC05-00OR22725
• OSTI ID: 1962984
• Alternate ID(s): OSTI ID: 1992292
• Report Number(s): JLAB-THY-22-3751; arXiv:2211.04434; DOE/OR/23177-5644
• Journal Information: Journal of High Energy Physics (Online), Journal Name: Journal of High Energy Physics (Online) Journal Issue: 3 Vol. 2023; ISSN 1029-8479
• Publisher: Springer NatureCopyright Statement
• Country of Publication: United States
• Language: English