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Quasiparton distribution functions in covariant quark models

F. Aslan1,3, A. Tandogan2, and P. Schweitzer3

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Phys. Rev. D 114, 076028 – Published 30 October, 2026

DOI: https://doi.org/10.1103/bl2f-xygk

Abstract

Quasiparton distribution functions (QPDFs) are defined in terms of QCD fields at spacelike separations evaluated in matrix elements of hadrons moving with velocity v. These objects can be studied in lattice QCD. In the limit when v approaches the speed of light, QPDFs converge to parton distribution functions. It is insightful to study QPDFs and their convergence in models. In this work, we first study the QPDFs in a broad class of quark models characterized by one common feature, namely the absence of gauge degrees of freedom. We provide general proofs for the convergence and sum rules of the unpolarized quark and antiquark QPDFs for both choices γ0 and γ3. We choose the covariant parton model as an illustration, and derive analytical results for the small-xv behavior of QPDFs and the energy-momentum tensor form factor c¯q(t) at zero momentum transfer. These results are of interest as they correspond to a Wandzura-Wilczek-type approximation.

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Phys. Rev. D 114, 076028– Published 30 October, 2026
  • Received 31 May 2026
  • Accepted 23 September 2026
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