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Transverse force tomography inside a proton from basis light-front quantization

Ziqi Zhang*, Chandan Mondal†, Siqi Xu‡, and Xingbo Zhao§

James P. Vary∥

  • *Contact author: zhangziqi@impcas.ac.cn
  • †Contact author: mondal@impcas.ac.cn
  • ‡Contact author: xsq234@impcas.ac.cn
  • §Contact author: xbzhao@impcas.ac.cn
  • ∥Contact author: jvary@iastate.edu
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Phys. Rev. D 114, 054011 – Published 8 September, 2026

DOI: https://doi.org/10.1103/sk7p-w8mg

Abstract

The twist-3 transverse spin-dependent nucleon structure function g2 arises in high-energy processes involving a transversely polarized nucleon. Its connection to quark-gluon correlations allows for an interpretation in terms of the average transverse color Lorentz force acting on unpolarized quarks inside a transversely polarized nucleon. In this work, we investigate this force using light-front wave functions obtained by diagonalizing the light-front Hamiltonian with quantum chromodynamics inputs within the basis light-front quantization approach. We evolve our results to a common scale of 5  GeV2 and present the corresponding form factors in momentum space as well as the transverse force components in impact-parameter space. These distributions provide a complementary perspective on the Sivers asymmetry in transversely polarized deep-inelastic scattering. In the forward limit, we extract the twist-3 reduced matrix element d2, and our results are found to be comparable with those from other theoretical calculations and experimental determinations.

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Phys. Rev. D 114, 054011– Published 8 September, 2026
  • Received 31 March 2026
  • Accepted 31 July 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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