Leading-twist proton parton distribution amplitude from scalar and axial-vector diquark correlations
Abstract
We compute the leading-twist proton parton distribution amplitude (PDA) using algebraic representations of the nucleon Faddeev wave function inspired by perturbation-theory integral representations. The PDA is obtained from a light-front projection of the covariant quark--diquark Faddeev amplitude and analysed in terms of its scalar- and axial-vector-diquark components. We derive analytic expressions for the corresponding diquark distribution amplitudes and their contributions to the proton PDA. The resulting distribution is broad and concave, with its maximum (x1,x2,x3)≈(0.55,0.20,0.25) displaced from the symmetric configuration $(1/3,1/3,1/3)$, which corresponds to the maximum of the perturbative-QCD asymptotic form. Scalar-diquark correlations generate a strong asymmetry in the longitudinal momentum distribution, whereas axial-vector correlations redistribute momentum among the valence quarks and significantly reduce this asymmetry. We calculate low-order Mellin moments and obtain a compact parametrisation of the proton PDA at the hadronic scale, μ0=0.51 GeV. We then perform the leading-order QCD evolution of its normalized shape to μ=2 GeV, finding that evolution reduces the momentum asymmetry while preserving a clear imprint of the non-perturbative quark--diquark correlations. The results provide insight into the role of such correlations in shaping the proton light-front structure and furnish non-perturbative input for studies of hard exclusive baryonic processes.
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BibTeX
@misc{almeidazamora2026leadingtwist,
title = {{Leading-twist proton parton distribution amplitude from scalar and axial-vector diquark correlations}},
author = {B. Almeida-Zamora and L. Albino and C. Mezrag and J. Segovia},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.22994},
eprint = {2610.22994},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.22994},
}
RIS
TY - UNPB
TI - Leading-twist proton parton distribution amplitude from scalar and axial-vector diquark correlations
AU - B. Almeida-Zamora
AU - L. Albino
AU - C. Mezrag
AU - J. Segovia
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.22994
UR - https://arxiv.org/abs/2610.22994
AB - We compute the leading-twist proton parton distribution amplitude (PDA) using algebraic representations of the nucleon Faddeev wave function inspired by perturbation-theory integral representations. The PDA is obtained from a light-front projection of the covariant quark--diquark Faddeev amplitude and analysed in terms of its scalar- and axial-vector-diquark components. We derive analytic expressions for the corresponding diquark distribution amplitudes and their contributions to the proton PDA. The resulting distribution is broad and concave, with its maximum (x_1,x_2,x_3)≈(0.55,0.20,0.25) displaced from the symmetric configuration $(1/3,1/3,1/3)$, which corresponds to the maximum of the perturbative-QCD asymptotic form. Scalar-diquark correlations generate a strong asymmetry in the longitudinal momentum distribution, whereas axial-vector correlations redistribute momentum among the valence quarks and significantly reduce this asymmetry. We calculate low-order Mellin moments and obtain a compact parametrisation of the proton PDA at the hadronic scale, μ_0=0.51 GeV. We then perform the leading-order QCD evolution of its normalized shape to μ=2 GeV, finding that evolution reduces the momentum asymmetry while preserving a clear imprint of the non-perturbative quark--diquark correlations. The results provide insight into the role of such correlations in shaping the proton light-front structure and furnish non-perturbative input for studies of hard exclusive baryonic processes.
ER -