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  • Open Access

String-based axial and helicity-flip GPDs: A comparison to lattice QCD

Florian Hechenberger*

Kiminad A. Mamo†

Ismail Zahed‡

  • Center for Nuclear Theory, Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA

  • Center for Nuclear Theory, Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA

  • *Contact author: florian.hechenberger@stonybrook.edu
  • †Contact author: kamamo@wm.edu
  • ‡Contact author: ismail.zahed@stonybrook.edu
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Phys. Rev. D 112, 074018 – Published 16 October, 2025

DOI: https://doi.org/10.1103/7lxw-g6tq

Abstract

We construct an analytic, string-based representation of the nucleon’s axial and helicity-flip conformal moments of generalized parton distributions (GPDs) that holds for any skewness and for both the quark and gluon channels. The starting point is the Mellin-Barnes resummation of the conformal partial-wave expansion, where the moments are parametrized by open- (Reggeon) and closed-string (Pomeron) trajectories with slopes determined by experimental form factors and meson/glueball spectroscopy. The forward limits are fixed by the empirical unpolarized and polarized parton distributions. Polynomiality, crossing symmetry, and support are satisfied by construction. After next-to-leading order Dokshitzer-Gribov-Lipatov-Altarelli-Parisi/Efremov-Radyushkin-Brodsky-Lepage evolution to μ=2  GeV our analytic framework (i) reproduces some of the currently available lattice moments of E and H˜ in the nonsinglet sector, (ii) predicts sea-quark and gluon polarized moments that will be testable by forthcoming simulations and experiments at Jefferson Lab and the future Electron-Ion Collider, and (iii) yields axial and helicity-flip GPDs in x-space in reasonable agreement with lattice QCD.

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References (46)

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Phys. Rev. D 112, 074018– Published 16 October, 2025
  • Received 6 August 2025
  • Accepted 30 September 2025
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