arXiv subjects

Wenbao Jia

Publications and source records attributed to Wenbao Jia.

9 recordsLinked to original sources

arXiv2026

Pion and $ρ$ meson's unpolarized quark distribution functions from $q\bar{q}$ and all Fock-states within Dyson--Schwinger equations

We compute the twist-2 unpolarized quark parton distribution functions (PDFs) of the pion and the $ρ$ meson within the Dyson-Schwinger equations (DSEs) framework using the rainbow-ladder (RL) truncation. A new DSE for the spin-1 hadron's quark-quark correlation matrix is derived, from which the PDFs can be extracted. For the $ρ$ meson, we obtain for the first time within RL-DSEs the unpolarized PDFs corresponding to different helicity states. A pronounced difference is observed between the $|Λ|=1$ and $Λ=0$ cases, where $Λ$ denotes the meson helicity, leading to a nonvanishing and numerically sizable tensor-polarized PDF $f_{1LL}(x)$. We further compare these results with those obtained under a leading Fock-state ($|q\bar{q}\rangle$) truncation and find substantial deviations. This comparison demonstrates that the present RL-DSEs framework incorporates higher Fock-state contributions associated with gluonic degrees of freedom, which has a significant impact on the quark distributions.

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arXiv2026

An imprint of intrinsic quark--gluon correlations: a nonmonotonic feature in $e(x)$

We present the first rainbow-ladder Dyson-Schwinger equations study of the pion's chiral-odd, twist-3 parton distribution $e_{\rm q}(x)$. By deriving a novel Dyson-Schwinger equation for the pion's quark-quark correlation matrix, we simultaneously extract from it both the unpolarized twist-2 parton distribution function $f_{\rm q}(x)$ and the twist-3 distribution $e_{\rm q}(x)$. Our results show that chiral symmetry strongly suppresses the twist-2 component of $e_{\rm q}(x)$, leaving the genuine twist-3 quark-gluon component dominant and featuring a node. We therefore argue that the genuine twist-3 term can make a substantial contribution to hadronic $e(x)$, producing a nonmonotonic structure that is a clear imprint of intrinsic quark-gluon correlations. We point out that the existence of a hump-like feature is compatible with, although not uniquely indicated by, recent proton extractions and awaits more precise determination.

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arXiv2025

Diffractive electroproduction of light vector particles: leading Fock-state contribution in the presence of significant higher Fock-state effects

We study exclusive diffractive production of vector mesons and photon using the color dipole model with leading Fock state light front wave functions derived from Dyson Schwinger and Bethe Salpeter equations. New results for the $ϕ$ meson and real photon are presented. Without data fitting, our calculation well matches HERA data in certain kinematical domains. The key finding of this paper is that in a color dipole model study for $ρ/γ$ and $ϕ$, where light quarks are involved, the leading $q\bar{q}$ approximation is valid only when $Q^2$ exceeds $20$ and 10 GeV$^2$ respectively, unlike $J/ψ$ which can be well described for $Q^2\approx 0$ GeV$^2$. This underscores the special role of $ϕ$ electroproduction in color dipole picture: it strikes a balance between the large dipole size typical of light mesons and the smaller size associated with high $Q^2$ photons, making it potentially well suited for probing gluon saturation effects.

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arXiv2024

Heavy flavor-asymmetric pseudoscalar mesons on the light front

We extract the leading Fock-state light front wave functions (LF-LFWFs) of heavy flavor-asymmetric pseudoscalar mesons $D$, $B$ and $B_c$ from their Bethe-Salpeter wave functions based on Dyson-Schwinger equations approach, and study their leading twist parton distribution amplitudes, generalized parton distribution functions and transverse momentum dependent parton distributions. The spatial distributions of the quark and antiquark on the transverse plane are given, along with their charge and energy distributions on the light front. We find that in the considered mesons, the heavier quarks carry most longitudinal momentum fraction and yield narrow $x$-distributions, while the lighter quarks play an active role in shaping the transverse distributions within both spatial and momentum space, exhibiting a duality embodying characteristics from both light mesons and heavy quarkonium.

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arXiv2023

Nonperturbative photon $q\bar{q}$ light front wave functions from a contact interaction model

We propose a method to calculate the $q\bar{q}$ light front wave functions (LFWFs) of photon at low-virtuality, i.e., the light front amplitude of $γ^*\rightarrow q\bar{q}$ at low $Q^2$, based on a light front projection approach. We exemplify this method using a contact interaction model within Dyson-Schwinger equations formalism and obtain the nonperturbative photon $q\bar{q}$ LFWFs. In this case, we find the nonperturbative effects are encoded in the enhanced quark mass and a dressing function of covariant quark-photon vertex, as compared to the leading order quantum electrodynamics photon $q\bar{q}$ LFWFs. We then use nonperturbative-effect modified photon $q\bar{q}$ LFWFs to study the inclusive deep inelastic scattering HERA data in the framework of the color dipole model. The results demonstrate that the theoretical description of data at low $Q^2$ can be significantly improved once the nonperturbative corrections are included in the photon LFWFs.

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arXiv2023

Transvese momentum dependent parton distributions of pion at leading twist

We calculate the leading twist pion unpolarized transverse momentum distribution $f_1(x,k_T^2)$ and the Boer-Mulders function $h_1^\perp(x,k_T^2)$, using leading Fock-state light front wave functions (LF-LFWFs) based on Dyson-Schwinger and Bethe-Salpeter equations. These DS-BSEs based LF-LFWFs provide dynamically generated s- and p-wave components, which are indispensable in producing chirally odd Boer-Mulders function that has one parton spin flipped. Employing a non-perturbative SU(3) gluon rescattering kernel to treat the gauge link of the Boer-Mulders function, we thus obtain both TMDs at hadronic scale and then evolve them to the scale of $μ^2=4.0$ GeV$^2$. We finally calculate the generalized Boer-Mulders shift and find it to be in agreement with the lattice prediction.

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arXiv2023

Unpolarized generalized parton distributions of light and heavy vector mesons

We study the leading-twist unpolarized generalized parton distributions (GPDs) of light and heavy vector mesons, i.e., the $ρ$, $J/ψ$ and $Υ$, at zero skewness. An ansatz incorporating the zero mode contribution is introduced to modify the light front overlap representation of GPDs. The leading Fock-state light front wave functions (LF-LFWFs) of vector mesons from DS-BSEs approach are then employed to study the meson GPDs. The light front spatial distribution of valence quarks within vector mesons is then studied with the impact parameter dependent GPD (IPD GPD). We also investigate the electromagnetic and gravitational form factors, which are the first and second Mellin moments of the GPDs. The light-cone mass radius of $ρ$ is determined to be 0.30 fm, close to a recent NJL model prediction 0.32fm. For $J/ψ$ and $Υ$, they are predicted to be 0.151fm and 0.089 fm respectively.

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arXiv2022

Transverse momentum distributions of valence quark in light and heavy vector mesons

We study the leading-twist time-reversal even transverse momentum dependent parton distribution functions (TMDs) of light and heavy vector mesons, i.e., the $ρ$, $J/ψ$ and $Υ$. We employ the leading Fock-state light front wave functions (LF-LFWFs) of $ρ$ and $J/ψ$ from our recent study, and supplement with $Υ$'s LF-LFWFs. These LF-LFWFs are extracted from dynamically solved Bethe-Salpeter wave functions. The vector meson TMDs are then studied with the light front overlap representation at leading Fock-state. All the obtained TMDs are non-vanishing and evolve with current quark mass, in particular the tensor polarized TMDs $f_{1LT}$ and $f_{1TT}$ which undergo a sign flip. The $ρ$ TMDs are compared with other model studies and agreement is found, aside from $f_{1LT}$ and $f_{1TT}$. Finally, the collinear PDFs of vector mesons are studied. The $ρ$'s valence PDFs $f_{1,v}(x)$ and $g_{1L,v}(x)$ are evolved to the scale of 2.4 GeV, with their first three moments compared to lattice QCD prediction. The qualitative behavior of tensor polarized PDF $f_{1LL}(x)$ in $ρ$ at large $x$ is also discussed.

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arXiv2021

Ground state pseudoscalar mesons on the light front: from the light to heavy sector

We extract the leading Fock-state light front wave functions (LF-LFWFs) of both the light and heavy pseudoscalar mesons, e.g., the pion (at masses of 130 MeV, 310 MeV and 690 MeV), $η_c$ and $η_b$, from their covariant Bethe-Salpeter wave functions within the rainbow-ladder (RL) truncation. It is shown that the LF-LFWFs get narrower in $x$ (the longitudinal momentum fraction of meson carried by the quark) with the increasing current quark mass, and the leading twist parton distribution amplitudes (PDAs) inherit this feature. Meanwhile, we find in the pion the LF-LFWFs only contribute around 30\% to the total Fock-state normalization, indicating the presence of significant higher Fock-states within. In contrast, in the $η_c$ and $η_b$ the LF-LFWFs contribute more than $90$\%, suggesting the $Q\bar{Q}$ valence Fock-state truncation as a good approximation for heavy mesons. We thus study the 3-dimensional parton distributions of the $η_c$ and $η_b$ with the unpolarized generalized parton distribution function (GPD) and the transverse momentum dependent parton distribution function (TMD). Through the gravitational form factors in connection with the GPD, the mass radii of the $η_c$ and $η_b$ in the light-cone frame are determined to be $r_{E,{\rm LC}}^{η_c} =0.150$ fm and $r_{E,{\rm LC}}^{η_b} =0.089$ fm respectively.

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