arXiv subjects

Chueng-Ryong Ji

Publications and source records attributed to Chueng-Ryong Ji.

At least 19 recordsLinked to original sources

arXiv2026

Quantum corrections as a Bound for Detecting Self-Interacting Ultralight Dark Matter

We investigate the implications of interactions between ultralight dark matter (ULDM) and Standard Model fermions for the radiative stability of the ULDM potential. By matching the heavy fermion onto a low-energy scalar effective field theory, we derive the one-loop threshold corrections to the ULDM mass and self-interaction couplings. We interpret these corrections in terms of radiative naturalness conditions. For the parameter region motivated by cosmological and galactic considerations, the quadratic correction provides the strongest naturalness criterion, while the direct and cubic-induced quartic corrections remain subdominant. Our results illustrate how radiative effects can constrain the parameter space satisfying our radiative-naturalness criterion based on threshold corrections.

hep-ph↗

arXiv2026

First simultaneous global QCD analysis of kaon and pion parton distributions with lattice QCD constraints

We perform the first simultaneous global QCD analysis of pion and kaon parton distribution functions (PDFs), constrained by pion- and kaon-induced Drell-Yan (DY) and leading neutron electroproduction data, together with lattice QCD data on pion and kaon PDF moments. The analysis indicates a softer valence $\bar u$ distribution in the $K^-$ than in the $π^-$, and a significantly more peaked valence $s$-quark density in $K^-$ compared with the $\bar u$. The effective exponent governing the high-$x$ behavior of the PDF is found to be larger for $\bar u$ in the kaon, $β_{\bar u}^{K^-}\!= 1.6(2)$, than in the pion, $β_{\bar u}^{π^-}\!= 1.16(4)$, in the range $0.7 \leq x \leq 0.95$. From the gluon momentum fractions we find the pion's gluon content accounts for $\approx 1/3$ of the mass budget of the pion at $μ=2~{\rm GeV}$, but only $\approx 1/4$ for the kaon.

hep-ph↗

arXiv2026

Origin of the Covariant Wigner Operator as a Quantum Amplitude in QCD

The Wigner function plays a central role in QCD as a phase space object encoding correlations among quarks, antiquarks, and gluons, yet its interpretation remains subtle due to its quasiprobabilistic nature and possible negativity. Recent work based on the Koopman-von Neumann-Sudarshan (KvNS) Hilbert space formulation of classical mechanics suggests the Wigner function arises as a quantum probability amplitude projected onto classical phase space, rather than a quasiprobability density (Bondar et al., 2013; McCaul et al., 2023). In the classical limit, this amplitude reduces to the classical Koopman wavefunction. In this work, we extend this perspective to relativistic QCD by constructing a Koopman description of the quark Wigner operator. We show that the Wigner operator is naturally isomorphic to a phase space spinor, providing a unified framework in which both classical and quantum dynamics are expressed. Within this formulation, the Wigner function retains its interpretation as an amplitude even in the relativistic regime. This viewpoint clarifies the origin of negativity and other nonclassical features, and provides a more transparent foundation for parton distribution functions in QCD. Remarkably, the relativistic Koopman framework reproduces the classical limit of QCD.

hep-ph↗

arXiv2026

Interpolating conformal algebra in $(1+1)$ dimensions between the instant form and the light-front form of relativistic dynamics

We present the interpolating conformal algebra between the instant form dynamics (IFD) and the light-front dynamics (LFD) in $(1+1)$ dimensions, along with a $4\times4$ interpolating projective spacetime matrix representation. While there are six generators in the $(1+1)$ dimensional conformal algebra, the number of kinematic and dynamic generators dramatically changes in LFD, maximizing (minimizing) the number of kinematic (dynamic) generators to four (two) with respect to two (four) kinematic (dynamic) generators in IFD, as well as in any other forms of dynamics between IFD and LFD. It confirms and signifies the utility of LFD, saving substantial dynamical efforts in solving the $(1+1)$ dimensional quantum field theories. We also present $2\times2$ Pauli matrix representation of $(1+0)$ and $(0+1)$ conformal groups, and creation/annihilation operators of quantum simple harmonic oscillator representations of $(1+0)$ dimensional conformal groups.

hep-th↗

arXiv2026

Quantum orientation entanglement analysis of the interpolating helicity states between the instant form dynamics and the light-front dynamics

The interplay between quantum orientation entanglement and Wigner rotation plays a fundamental role in understanding the behavior of spin angular momentum in quantum states. To analyze the quantum orientation entanglement of the relativistic helicity states interpolating between the Jacob-Wick helicity and the light-front helicity, we examine the relative angle between the particle's momentum direction and the spin orientation for the interpolating helicity states. For this analysis, we introduce a novel method for expanding the interpolating helicity states in terms of the Jacob-Wick helicity. The corresponding probabilistic coefficients follow the structure of the Wigner d-matrix elements, which we use for the interpretation of the quantum orientation entanglement manifested in the angular distributions of the interpolating scattering helicity amplitudes. As an explicit demonstration, we compute the interpolating helicity amplitudes for the pair production of spin-1 (vector) particles in the annihilation of two spin-0 (scalar) particles, focusing primarily on their contact interaction. In particular, we identify the critical interpolation angle that bifurcates the dynamical branches between the instant-form dynamics and the light-front dynamics and discuss the underlying orientation entanglement in the interpolating helicity amplitudes.

hep-th↗

arXiv2026

Kaon T-even transverse-momentum-dependent distributions and form factors in a self-consistent light-front quark model

We present a self-consistent light-front quark model (LFQM) for the kaon based on the Bakamjian--Thomas (BT) construction and apply it to the electromagnetic and scalar form factors, as well as the full set of unpolarized T-even transverse-momentum-dependent distributions (TMDs) and their collinear parton distribution functions (PDFs). A uniform implementation of the invariant mass $M_0$ in both the hadronic matrix elements and the associated Lorentz structures enforces four-momentum conservation at the meson--quark vertex and yields current-component--independent observables by consistently incorporating the light-front zero-mode structure required by covariance. The electromagnetic form factor $F_{K^+}(Q^2)$ is demonstrated to be unique by explicit computation from all available current components ($γ^+$, $γ^\perp$, and $γ^-$). In the scalar channel, we compare the direct $f_S(Q^2)$ and mass-factored $F_S(Q^2)$ definitions and show that they are not interchangeable within the BT-based LFQM, since the replacement $M\!\to\!M_0(x,\bm{k}_\perp)$ must be implemented at the integrand level. Using a Gaussian light-front wave function, the twist-2 TMD $f_1^q$ exhibits an exact Gaussian dependence in $\bm{k}_\perp$, while higher-twist TMDs ($f^{\perp q}$, $e^q$, $f_4^q$) display systematic twist and flavor hierarchies. We further analyze the perturbative QCD evolution of the valence PDFs for the pion and kaon and report their Mellin moments at representative scales, enabling direct comparison with phenomenology.

hep-ph↗

arXiv2026

Long Range Outlook for Short-Range Correlations

Short range correlated (SRC) N N pairs are pairs of nucleons with high relative momentum (prel > kF where kF ~ 250 MeV/c is the Fermi momentum in medium to heavy nuclei) and lower center of mass momentum. The motivation for studying SRC pairs ranges from a desire to achieve a more comprehensive understanding of the many-body nuclear wave-function at high-resolution to searching for explicit QCD-dynamics effects within the nuclear medium, not to mention connections to many other open problems in nuclear physics. Exploring short-range correlations was one of the physics motivations for building CEBAF (now Jefferson Lab). Scientists used the high luminosity and high energy of this cutting-edge machine to find kinematics that cleanly showed the signals of short-range correlations. This paved the way in the last two decades for tremendous progress understanding these correlations. This paper reviews recent progress and highlights outstanding questions and areas that need further study.

nucl-ex↗

arXiv2025

The (3+1)-dimensional scalar field model analysis of beam spin asymmetry in the electroproduction of a scalar meson off a scalar target

We explore exclusive scalar meson electroproduction off a scalar target in the (3+1)-dimensional scalar field model. This model analysis is a straightforward extension of the previous (1+1)-dimensional model analysis presented in Phys. Rev. D \textbf{105}, 096014 (2022). In contrast to the (1+1)-dimensional model, the (3+1)-dimensional model allows us to compute the beam spin asymmetry (BSA), which is proportional to the imaginary part of the product of the two Compton form factors (CFFs) that appear in the hadronic current of the present scalar meson electroproduction process. We compute both real and imaginary parts of the CFFs and note that the BSA is detectable for $-t/Q^2 \gtrsim 0.1$ although it gets quite small in the kinematic region $-t/Q^2 \ll 0.1$ where the factorization of the generalized parton distribution (GPD) is attainable. We find the analytic forms of the leading twist GPD for the DGLAP and ERBL regions in the (3+1)-dimensional scalar field model, confirming its uniqueness independent of the hadronic current component. While we verify that the GPD sum rule for the total result of summing the DGLAP and ERBL regions holds for all components of the hadronic current, we note that the respective correspondence of the DGLAP and ERBL regions to the valence and non-valence parts of the electromagnetic form factor holds only for the light-front plus component of the hadronic current but not for any other components of the hadronic current. We discuss the polynomiality of the GPD up to the second moments and remark on accessible ranges of kinematics to measure the BSA and CFFs with respect to the future experimental efforts of extracting the leading-twist GPDs.

hep-ph↗

arXiv2025

The Feynman path integral formulation of non-dispersive Airy wave packets and their applications to the heavy meson mass spectra and ultra-cold neutrons

We demonstrate the non-spreading behavior of Airy wave packets utilizing the Feynman path integral formulation of a linear potential, the Airy functions' zeros correspondence to heavy-meson mass spectroscopy, and their implications to the eigenstates of ultra-cold neutrons in Earth's gravitational field. We derive the linear kernel, and utilize the Feynman path integral time evolution to show that Airy function wave packets are non-dispersive in free space. We then model the confining contribution to 1S - 2S heavy meson mass gaps as a 1+1D absolute linear potential and look at the correspondence of the Airy function zeros. In doing so, we predicted the confining contribution to the mass gap of heavy mesons with a good accuracy when compared to calculations performed in the light front. Furthermore, we used these Airy function solutions to model the quantum states of a neutron under Earth's gravity. We show that the measured heights of a neutron can be modeled by the zeros of the Airy function, and compare to experimental data and predictions utilizing the WKB approximation.

hep-ph↗

arXiv2025

Axial Anomaly and Confinement in Two-dimensional QED: Singular Behavior of Vacuum Polarization at Threshold

Performing the perturbative calculation of the vacuum polarization amplitude in QED1+1, one finds an anomalous axial vector Ward identity. We note that the photon self-energy function displays a singularity in the 1+1D case, in stark contrast to the 3+1D case. We discuss the nature of this singularity and its physical implications from the perspectives of axial anomaly and confinement in two-dimensional QED. Computing the total cross section of $e^+e^-\to μ^+μ^-$ and displaying the toy version of the R ratio in 1+1D with respect to the typical R ratio in 3+1D, we discuss the significance of using the dressed photon propagator in obtaining the finite cross section.

hep-th↗

arXiv2025

Nonlocal effective field theory and its applications

We review recent applications of nonlocal effective field theory, focusing in particular on nonlocal chiral effective theory and nonlocal quantum electrodynamics (QED), as well as an extension of nonlocal effective theory to curved spacetime. For the chiral effective theory, we discuss the calculation of generalized parton distributions (GPDs) of the nucleon at nonzero skewness, along with the corresponding gravitational (or mechanical) form factors, within the convolution framework. In the QED application, we extend the nonlocal formulation to construct the most general nonlocal QED interaction, in which both the propagator and fundamental QED vertex are modified due to the nonlocal Lagrangian, while preserving the Ward-Green-Takahashi identities. For consistency with the modified propagator, a solid quantization is proposed, and the nonlocal QED is applied to explain the lepton $g-2$ anomalies without the introduction of new particles or interactions. Finally, with an extension of the chiral effective action to curved spacetime, we investigate the nonlocal energy-momentum tensor and gravitational form factors of the nucleon with a nonlocal pion-nucleon interaction.

hep-ph↗

arXiv2025

Quantum Scales of Galaxies from Self-interacting Ultralight Dark Matter

We derive the characteristic scales for physical quantities of dwarf galaxies, such as mass, size, acceleration, and angular momentum, within the self-interacting ultralight dark matter (ULDM) model. Due to the small mass of ULDM, even minor self-interactions can drastically alter these scales in the Thomas-Fermi limit. We suggest that these characteristic scales are connected to mysteries of observed galaxies. Oscillation of ULDM field can explain the current cosmological density of dark matter. Many cosmological constraints suggest that the energy scale $\tilde{m}$ for self-interacting ULDM is typically of the order $10~eV$, whereas the mass $m$ for the non-interacting case is around $10^{-21}~eV$. Self-interacting ULDM provides the better explanation for cosmological observations than the non-interacting case.

astro-ph.GA↗

arXiv2025

Beyond leading twist: $ρ$ meson decay constants and distribution amplitudes in a self-consistent light-front quark model

In this study, we present a comprehensive analysis of decay constants and chiral-even and chiral-odd distribution amplitudes (DAs) up to twist 4 for the $ρ$ meson in the standard light-front quark model (LFQM) based on the Bakamjian-Thomas (BT) construction. For the $ρ$ meson, which possesses both longitudinal $(h=0)$ and transverse $(h=\pm 1)$ polarizations, two types of decay constants, $f_ρ^{\parallel}$ and $f_ρ^{\perp}$, arises accordingly. We demonstrate that these decay constants can be self-consistently extracted from both local ($z^μ=0$) and nonlocal ($z^μ\neq 0$) matrix elements $\langle 0 | \bar{q}(z)\, Γ\, q(-z) | ρ(P,h) \rangle$, with $Γ= (γ^μ, σ^{μν}, γ^μγ_5, \mathbf{1})$, in a manner independent of current components, polarizations, and reference frames. In particular, we emphasize the role of nonlocal matrix elements involving axial-vector and scalar currents, where mixing between $f_ρ^{\parallel}$ and $f_ρ^{\perp}$ occurs. We show that this mixing is consistently resolved through the BT construction, ensuring the proper extraction of these decay constants. Additionally, we investigate the structure of chiral-even DAs ($ϕ_{2;\mathrm{V}}^\parallel, ϕ_{3;\mathrm{V}}^\parallel, ψ_{3;\mathrm{A}}^\perp, ϕ_{4;\mathrm{V}}^\parallel$) and chiral-odd DAs ($ϕ_{2;\mathrm{T}}^\perp, ϕ_{3;\mathrm{T}}^\perp, ψ_{3;\mathrm{S}}^\parallel, ϕ_{4;\mathrm{T}}^\perp$) beyond leading twists, and present their corresponding $ξ$-moments and Gegenbauer moments. These results provide deeper insight into the nonperturbative structure of vector mesons and demonstrate the robustness and self-consistency of the LFQM based on the BT framework.

hep-ph↗

arXiv2025

Structure of lightest nuclei in the visible Universe

The simplest atomic nucleus, deuteron, provides key insights into the strong nuclear interactions among quarks and gluons that shape the visible universe. We present the first attempt to calculate the internal structure of the deuteron by incorporating hidden-color degrees of freedom, modeling it as an effective mixture of singlet-singlet and octet-octet color clusters beyond the traditional proton-neutron picture. By employing the separation of variables for the light-front two-cluster bound-state equation, we explore how these hidden color correlations shape both its spin and electromagnetic structure. We incorporate the transverse and longitudinal dynamics by two Schrödinger-like equations, namely the light-front holography and the 't Hooft equation, respectively. Our predictions of the electromagnetic form factors and structure functions, including tensor-polarized function, align well with experimental data, offering insights into the partonic structure of the deuteron. Its tensor property could pave the way for a new era in spin physics, guiding future experimental investigations.

hep-ph↗

arXiv2024

Off-shell pion properties: electromagnetic form factors and light-front wave functions

The off-shell pion electromagnetic form factors are explored with corresponding off-shell light-front wave functions modeled by constituent quark and anti-quark. We apply the Mandelstam approach for the microscopic computation of the form factors relating the model parameters with the pion decay constant and charge radius. Analyzing the existing data on the cross-sections for the Sullivan process, H(e,e',pi)n, we extract the off-shell pion form factor using the relation derived from the generalized Ward-Takahashi identity for the pion electromagnetic current. They are compared with our previous results from exactly solvable manifestly covariant model of a (3+1)-dimensional fermion field theory. We find that the adopted constituent quark model reproduces the extracted off-shell form factor $F_1(Q^2,t)$ from the experimental data within a few percent difference and matches well with our previous theoretical simulation which exhibits a variation of about 10\% for the extracted off-shell pion form factor $g(Q^2,t)$. We also identify the pion valence parton distribution function (PDF) and transverse momentum distribution (TMD) in terms of the light-front wave function and discuss their off-shell properties.

hep-ph↗

arXiv2024

Nonlocal chiral contributions to generalized parton distributions of the proton at nonzero skewness

We compute the one-loop contributions to spin-averaged generalized parton distributions (GPDs) in the proton from pseudoscalar mesons with intermediate octet and decuplet baryon states at nonzero skewness. Our framework is based on nonlocal covariant chiral effective theory, with ultraviolet divergences regularized by introducing a relativistic regulator derived consistently from the nonlocal Lagrangian. Using the splitting functions calculated from the nonlocal Lagrangian, we find the nonzero skewness GPDs from meson loops by convoluting with the phenomenological pion GPD and the generalized distribution amplitude, and verify that these satisfy the correct polynomiality properties. We also compute the lowest two moments of GPDs to quantify the meson loop effects on the Dirac, Pauli and gravitational form factors of the proton.

hep-ph↗

arXiv2024

Mixing effects on spectroscopy and partonic observables of mesons with logarithmic confining potential in a light-front quark model

Using the variational principle, we systematically investigate the mass spectra and wave functions of both $1S$ and $2S$ state heavy pseudoscalar $(P)$ and vector $(V)$ mesons within the light-front quark model. This approach incorporates a Coulomb plus logarithmic confinement potential to accurately describe the constituent quark and antiquark dynamics. Additionally, spin hyperfine interactions are introduced perturbatively to compute the masses of pseudoscalar and vector mesons. The present analyses of the $1S$ and $2S$ states require the consideration of mixing between them to account for empirical constraints. These constraints include the mass gap $ΔM_{P} > ΔM_{V}$, where $ΔM_{P(V)} = M^{2S}_{P(V)} - M^{1S}_{P(V)}$ and the hierarchy of the decay constants $f_{1S} > f_{2S}$. We find the optimal value of the mixing angle to be $θ= 18^{\circ}$, significantly enhancing the consistency between our spectroscopic predictions and the experimental data compiled by the Particle Data Group (PDG). Furthermore, based on the predicted mass, the newly observed resonance $B_J(5840)$ could be assigned as a $2^1S_0$ state in the $B$ meson family. The study also reports various pertinent observables, including twist-2 distribution amplitudes, electromagnetic form factors, charge radii, $ξ$ moments, and transition form factors which are found to be consistent with both available lattice simulations and experimental data. In addition, our predicted branching ratios for the channels of $B^+ \rightarrow τ^+ ν_τ$ as well as rare decays of $B^0$ and $B_s^0$ appear in accordance with experimental data.

hep-ph↗

arXiv2024

Consistency of pion form factor and unpolarized transverse momentum dependent parton distributions beyond leading twist in the light-front quark model

We investigate the interplay among the pion's form factor, transverse momentum dependent distributions (TMDs), and parton distribution functions (PDFs) extending our light-front quark model (LFQM) computation based on the Bakamjian-Thomas construction for the two-point function[41,42] to the three-point and four-point functions. Ensuring the four-momentum conservation at the meson-quark vertex from the Bakamjian-Thomas construction, the meson mass is taken consistently as the corresponding invariant meson mass both in the matrix element and the Lorentz factor in our LFQM computation. We achieve the current-component independence in the physical observables such as the pion form factor and delve into the derivation of unpolarized TMDs and PDFs associated with the forward matrix element. We address the challenges posed by twist-4 TMDs and exhibit the fulfillment of the sum rule. Effectively, our LFQM successfully handles the light-front zero modes and offers insights for broader three-point and four-point functions and related observables.

hep-ph↗