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Kaiyu Fu

Publications and source records attributed to Kaiyu Fu.

11 recordsLinked to original sources
arXiv2026

Heavy mesons with dynamical gluon on the light front

We investigate the structure of charmonium, bottomonium, and $\rm B_c$ meson systems within the Basis Light-Front Quantization (BLFQ) approach, including both the quark-antiquark ($|q\bar{q}\rangle$) and quark-antiquark-gluon ($|q\bar{q}g\rangle$) Fock sectors. Our input light-front Hamiltonian incorporates a confining potential inspired by light-front holography, as well as the quark-gluon interaction from Quantum Chromodynamics. By adjusting model parameters to reproduce the mass spectra for low-lying states, we obtain the light-front wave functions for the heavy meson states. Based on these wave functions, we calculate electromagnetic form factors, decay constants, parton distribution amplitudes (PDAs), and parton distribution functions (PDFs) of the quarks and gluons in the heavy mesons. Our results for the charge radii and decay constants reasonably agree with experimental data and other theoretical approaches. The PDAs are consistent with the predictions from the earlier BLFQ calculations with an effective one-gluon exchange interaction. Furthermore, we present the first predictions within the BLFQ framework for the gluon PDFs in heavy mesons based on the light-front wave function in the $|q\bar{q}g\rangle$ sector.

hep-ph↗
arXiv2026

Coupled charm and charmonium transport in a strongly coupled quark-gluon plasma

The quark-gluon plasma (QGP) is a strongly coupled medium in which both open and hidden charm particles experience substantial nonperturbative interactions. This poses a major challenge for a quantitative description of charmonium transport in ultra-relativistic heavy-ion collisions, as it requires a mutually consistent treatment of pertinent transport coefficients. In this work, we present a coupled charm-charmonium transport framework for a strongly coupled QGP based on thermodynamic $T$-matrix interactions with recent constraints from Wilson-line correlators (WLCs) computed in lattice QCD. For the first time, the same underlying heavy-light interactions and in-medium spectral functions are used to self-consistently evaluate charm-quark diffusion and charmonium kinetics. In particular, the charmonium equilibrium limit, a critical transport parameter for regeneration, is evaluated in the presence of broad spectral functions. Charm-quark diffusion is simulated via Langevin dynamics and coupled to a Boltzmann equation for charmonium dissociation and regeneration. The equilibrium limit of the statistical model is recovered once charm quarks thermalize, and its extension to describe off-equilibrium is constructed. Preliminary applications to charmonium observables in Pb--Pb collisions at the LHC capture the measured centrality and momentum dependence fairly well.

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arXiv2026

Helium-3 relativistic wave function in light-front dynamics

The relativistic wave function of $^3$He nucleus is calculated in the framework of Light-Front Dynamics. It is determined by 32 spin-isospin components, each of which depends on five scalar variables. For NN interaction, the one-boson exchange model is assumed, but without a potential approximation. The relativistic effects manifest themselves in deviation of the relativistic components from the non-relativistic input, in the appearance of the components absent in the non-relativistic limit, and in dependence of solutions on specific variables that don't exist in the non-relativistic wave function.

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arXiv2025

Dynamical gluon effects in the three-dimensional structure of pion

We investigate the internal structure of the pion, including the contributions from one dynamical gluon, using the basis light-front quantization (BLFQ) approach. By solving a light-front QCD Hamiltonian with a three-dimensional confining potential, we obtain the light-front wavefunctions (LFWFs) for both the quark-antiquark and quark-antiquark-gluon Fock sectors. These wavefunctions are then employed to compute the unpolarized generalized parton distributions (GPDs) and the transverse-momentum-dependent parton distributions (TMDs) of valence quarks and gluons. We also extract the transverse spatial distributions, providing the squared radii of quark and gluon densities in the impact-parameter space. This work contributes toward a three-dimensional understanding of the pion's internal structure in both momentum and coordinate space.

hep-ph↗
arXiv2025

Relativistic $^3$He light-front wave function

The relativistic light-front (LF) wave function of $^3$He is determined by the three-body LF equation for the Faddeev components in the momentum space. As an interaction, we take the one-meson exchange kernels, without the potential approximation. Within the explicitly covariant formulation of LF dynamics, we calculate the full relativistic $^3$He LF wave function, comprising 32 spin-isospin components. In the non-relativistic domain, five of these components dominate and closely resemble their non-relativistic counterparts. Relativistic effects manifest themselves in deviations in relativistic domain of these components from the non-relativistic ones and in appearance of new components.

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arXiv2022

Light mesons with one dynamical gluon within basis light-front quantization

We investigate the structure of the light meson with one dynamical gluon from the light-front QCD Hamiltonian, determined for their constituent quark-antiquark and quark-antiquark-gluon Fock sectors, together with a three-dimensional confinement. After fitting the light meson mass spectroscopy, the light-front wave functions provide a good quality description of the pion electromagnetic form factor, and the valence quark distribution functions following QCD scale evolution.

hep-ph↗
arXiv2021

Light mesons with one dynamical gluon on the light front

We obtain the light meson mass spectroscopy from the light-front quantum chromodynamics (QCD) Hamiltonian, determined for their constituent quark-antiquark and quark-antiquark-gluon Fock components, together with a three-dimensional confinement. The eigenvectors of the light-front effective Hamiltonian provide a good quality description of the pion electromagnetic form factor, decay constant, and the valence quark distribution functions following QCD scale evolution. We also show that the pion's gluon densities can be probed through the pion-nucleus induced $J/\psi$ production data. Our pion parton distribution functions provide excellent agreement with $J/\psi$ production data from widely different experimental conditions.

hep-ph↗
arXiv2021

Positronium: an illustration of nonperturbative renormalization in a basis light-front approach

We calculate the mass spectrum and the structure of the positronium system at a strong coupling in a basis light-front approach. We start from the light-front QED Hamiltonian and retain one dynamical photon in our basis. We perform the fermion mass renormalization associated with the nonperturbative fermion self-energy correction. We present the resulting mass spectrum and wave functions for the selected low-lying states. Next, we apply this approach to QCD and calculate the heavy meson system with one dynamical gluon retained. We illustrate the obtained mass spectrum and wave functions for the selected low-lying states.

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arXiv2020

Recent Progress in Basis Light-front Quantization

Basis Light-front Quantization (BLFQ) is a nonperturbative approach to quantum field theory. In this paper, we report our recent progress in applying BLFQ to the positronium system in QED and to the meson and the baryon system in QCD. We present preliminary results on the mass spectrum, light-front wave functions and other observables of these systems, where one dynamical gauge boson is retained for the positronium and meson systems.

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arXiv2020

Positronium on the light front

Basis Light-front Quantization (BLFQ) is a newly developed nonperturbative approach, aiming at solving relativistic bound systems based on the Hamiltonian formalism of light-front dynamics. In this work, we introduce its application to the positronium system at strong coupling, $\alpha = 0.3$, with a dynamical photon mediating the interaction between the positron and the electron. Nonperturbative mass renormalization is needed to cancel the fermion self-energy divergence. Here, we present the resulting mass spectrum, light-front wave functions (LFWFs), and the photon distribution inside positronium.

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