arXiv subjects

Liang-Zhen Wen

Publications and source records attributed to Liang-Zhen Wen.

11 recordsLinked to original sources

arXiv2026

Investigation of S-wave tetraquark bound and resonant states with all Jacobi coordinates

We systematically explore the $S$-wave tetraquark systems $Qs\bar{n}\bar{n}$, $QQ\bar{n}\bar{n}$, $QQ\bar{Q}\bar{Q}$, and $ss\bar{s}\bar{s}$ ($Q=c,b$; $n=u,d$) within the constituent quark potential model. We incorporate all K-type Jacobi coordinates in addition to the conventional H-type configurations, optimize the basis expansion via a stochastic parameter generation strategy, and apply the complex scaling method to identify bound and resonant states. Our calculations demonstrate that while conventional H-type configurations suffice for low-lying states such as the $T_{cc}(3875)^+$ molecular candidate, the inclusion of K-type configurations becomes important for extracting highly excited resonances, allowing higher-energy resonances absent in H-only calculations to be identified. Furthermore, we identify resonance candidates for the $T_{cs0}(2900)$, $X(6900)$, and $X(7200)$, whereas the absence of fully-strange compact poles below 2.6 GeV challenges the interpretation of $ϕ(2170)$ and $X(2370)$ as $S$-wave compact $s s \bar{s} \bar{s}$ tetraquarks.

hep-ph↗

arXiv2026

Bound and Resonant Spectra of Few-Lepton Coulomb Systems

We present a unified calculation of bound and resonant states in purely leptonic Coulomb systems: $e^-e^-e^+$ ($\mathrm{Ps}^-$), $μ^+e^-e^-$ ($\mathrm{Mu}^-$), $μ^+μ^+e^-$ ($\mathrm{Mu}_2^+$), $e^+e^+e^-e^-$ ($\mathrm{Ps}_2$), and $μ^+μ^+e^-e^-$ ($\mathrm{Mu}_2$). Using an extended stochastic variational method combined with the complex scaling method, we resolve the natural-parity $S$- and $P$-wave spectra. Near their respective $n=2$ thresholds, all three trilepton systems exhibit Gailitis--Damburg sequences generated by $2S$ and $2P$ Stark mixing and the resulting inverse-square attraction. Although microscopically distinct from the Efimov effect, this mechanism produces the same inverse-square asymptotics and geometric scaling. The $\mathrm{Ps}^-$ and $\mathrm{Mu}^-$ systems exhibit resonance sequences of comparable density, whereas the $\mathrm{Mu}_2^+$ produces a much denser spectrum, with 20 resolved members in the $^3P^o$ channel. In $\mathrm{Mu}_2^+$, the deeper states follow molecular Born--Oppenheimer configurations, while the near-threshold spectrum is governed by the atomic $\mathrm{Mu}(2)+μ^+$ structure. In $\mathrm{Ps}_2$, coupling between threshold-degenerate configurations is essential for a near-threshold bound state. In $\mathrm{Mu}_2$, the Born--Oppenheimer organization of the resonance spectrum is channel dependent.

physics.atom-ph↗

arXiv2026

The excited baryon spectrum from a unified quark model

A common approach to studying the multiquark states is to solve the few-body Schrödinger equation within a quark potential model. The multiquark states may contain quarks with several different flavors and have richer color structures than ordinary hadrons. The reliability of such an investigation requires that the underlying quark potential model can simultaneously describe the meson and baryon spectra across all flavor sectors, including orbital and radial excitations, with a single parameter set. At present, no quark potential model fully satisfies this requirement. We construct a simple nonrelativistic constituent quark potential model that includes spin--orbit and tensor interactions. We refit the model parameters to the latest experimental data. The excited light hadrons and several exotic hadron candidates are excluded from the fit. The resulting parameter set reproduces the spectra across all fitted sectors. The vast majority of deviations are below 20 MeV, while the largest deviations remain of the order of several tens of MeV, which is the typical accuracy of nonrelativistic quark potential models. Using the same parameters, we predict the spectra and internal structures of the orbitally and radially excited heavy baryons, which await further experimental determination. The excited light baryons are calculated with the same parameters. The calculated excited light baryon spectra deviate substantially from experimental values. Our refitted model does not resolve these longstanding discrepancies. The results delimit the range of validity of the nonrelativistic constituent quark potential model. By treating mesons and baryons across all flavor sectors, including both orbital and radial excitations within a unified framework, the model provides a controlled starting point for few-body calculations of multiquark states. We also urge experimental searches for the predicted states.

hep-ph↗

arXiv2026

Spin-dependent polarizabilities of heavy vector mesons

We investigate the spin-dependent electromagnetic polarizabilities of the heavy vector mesons $D^*$ and $B^*$ in heavy meson chiral perturbation theory up to $\mathcal O(p^3)$. Using a twelve-element tensor basis for the real-photon Compton scattering on a spin-1 target, we determine two scalar, four vector and six tensor polarizabilities. We take the charm- and bottom-sector axial couplings from the measured $D^*$ width and lattice-QCD calculations, respectively, and estimate the magnetic couplings in the nonrelativistic constituent-quark model. In the charm sector, the proximity of the charged $Dπ$ thresholds generates strongly nonanalytic $Pϕ$-loop contributions, producing large real contributions to several $\bar D^{*0}$ polarizabilities and sizable imaginary parts for $D^{*-}$, whose charged $Dπ$ channel is open. The $E1E1$-type polarizabilities are enhanced much more strongly than their $M1M1$-type counterparts, consistent with the velocity suppression of the pion-cloud magnetic coupling. No analogous enhancement occurs for $B^*$: the Born terms govern the magnetic polarizabilities, and the anomaly poles dominate the vector polarizabilities that receive no Born contribution. These results resolve the spin dependence of the $Dπ$ threshold effect and provide benchmarks for future lattice-QCD studies.

hep-ph↗

arXiv2026

Meson-Nucleus Bound States with Neural-Network Quantum States

We present the first systematic calculations of $ϕ$-, $η_c$-, and $J/ψ$-nucleus ground states up to mass number $A{=}12$ based on the HAL QCD meson-nucleon potentials at near-physical point. The $(A{+}1)$-body Schrödinger equation is solved with a neural-network variational Monte Carlo framework, generalized to incorporate mesonic degrees of freedom. Benchmarking on light nuclei from $^2$H to $^{12}$C yields ground-state energies consistent with experiment. Meson-nucleus bound states emerge at $A\ge2$ for $ϕ$, $A\ge4$ for $J/ψ$, and $A\ge6$ for $η_c$. The $ϕ$-nucleus systems exhibit the strongest binding, with binding energies reaching tens of MeV. The $J/ψ$-nucleus and $η_c$-nucleus systems are weakly bound at the few-MeV and sub-MeV scale, respectively. The binding energy per nucleon deepens nearly linearly with $A$ for charmonium systems, whereas the $ϕ$-nucleus system exhibits a non-monotonic behavior peaking at $^4$He -- a distinctive hallmark of the short-range and strongly attractive $ϕN$ interaction. The meson compresses the nucleon distribution relative to the parent nucleus, and evolves from a halo configuration to one embedded inside the nucleus with increasing $A$. Our results provide predictions for future experimental searches, and establish a quantitative bridge between lattice QCD meson-nucleon interactions and the emergent many-body phenomena in meson-nucleus bound states.

hep-ph↗

arXiv2026

Electromagnetic polarizabilities of the triplet hadrons in heavy hadron chiral perturbation theory

We investigate the electromagnetic polarizabilities of singly heavy mesons and doubly heavy baryons within the framework of heavy hadron chiral perturbation theory up to $\mathcal{O}(p^3)$. We estimate the low-energy constants using the non-relativistic constituent quark model. A striking prediction of our study is the giant electric polarizabilities of the $D^*$ mesons: $α_E(\bar{D}^{*0}) \approx 291.4 \times 10^{-4} \text{fm}^3$ and $α_E(D^{*-}) \approx -0.4-64.4 i \times 10^{-4} \text{fm}^3$. These anomalously large values arise from the near-degenerate mass between $D^*$ and $D π$, which are orders of magnitude larger than those of their bottom counterparts. This kinematic coincidence induces a pronounced cusp structure in the chiral loops, reflecting the long-range dynamics of a pion cloud. For doubly heavy baryons, polarizabilities depend strongly on heavy-flavor composition: the $bcq$ system differs markedly from $ccq$ and $bbq$ due to mixing with scalar heavy-diquark states. Using heavy diquark-antiquark symmetry (HDAS), we unify the chiral dynamics of singly heavy mesons and doubly heavy baryons in the heavy-quark limit. The pion-loop contributions dominate the electromagnetic structure of heavy hadrons and provide essential benchmarks for future lattice QCD simulations.

hep-ph↗

arXiv2025

Bound and Resonant States of Muonic Few-Body Coulomb Systems: Extended Stochastic Variational Approach

We compute the bound and resonant states of hydrogen-like muonic ions ($μμp$, $μμd$, $μμt$) and three-body muonic molecular ions ($ppμ$, $pdμ$, $ptμ$, $ddμ$, $dtμ$, $ttμ$), and the four-body double-muonic hydrogen molecule ($μμpp$) using an extended stochastic variational method combined with complex scaling. The approach provides a unified treatment of bound and quasibound states and achieves an energy accuracy better than $0.1~\mathrm{eV}$ across all systems studied. Complete spectra below the corresponding $n=2$ atomic thresholds are obtained, including several previously unresolved shallow resonances in both three- and four-body sectors.

physics.atom-ph↗

arXiv2025

Electromagnetic polarizabilities of the spin-$\frac{3}{2}$ baryons in heavy baryon chiral perturbation theory

We employ Heavy Baryon Chiral Perturbation Theory (HB$χ$PT), a non-relativistic effective field theory that treats baryons as heavy static sources, to calculate the electromagnetic polarizabilities of spin-3/2 baryons in two sectors: the light-flavor decuplet baryons and singly heavy sextet baryons. We derive the analytical expressions up to $\mathcal{O}\left(p^3\right)$. Our results indicate that the long-range chiral corrections provide substantial contributions to the polarizabilities. In addition, magnetic dipole (M1) transitions of the baryons can significantly affect the magnetic polarizabilities and may even reverse their signs. For the decuplet baryons, the $Δ^+$ and $Δ^0$ exhibit the largest electric polarizabilities. Their values, $α_E(Δ^+) = (17.5 \pm 9.5)\times 10^{-4} \, \mathrm{fm}^3$ and $α_E(Δ^0) = (17.0 \pm 9.3)\times 10^{-4} \, \mathrm{fm}^3$, significantly exceed those typically observed for nucleons. Meanwhile, the electric polarizabilities of spin-3/2 singly heavy baryons are comparable to those of their spin-1/2 partners.

hep-ph↗

arXiv2025

The ${ϕNN,J/ψNN,η_c NN}$ systems based on HAL QCD interactions

We investigate the existence of bound states and resonances in the ${ϕNN, J/ψNN, η_c NN}$ systems using HAL QCD interactions for ${ϕN, J/ψN}$, and ${η_c N}$. We employ the Gaussian expansion method to solve the complex-scaled Schrödinger equation and find no resonances or bound states in the ${J/ψNN}$ and ${η_c NN}$ systems. We estimate the interaction between charmonium and nuclei, concluding that the $J/ψ$ or $η_c$ is likely to bind with ${}^3\mathrm{H}$, ${}^3\mathrm{He}$, ${}^4\mathrm{He}$, and heavier nuclei. For the $ϕNN$ system, the lattice QCD $ϕN\left({ }^2 S_{1 / 2}\right)$ interaction is absent. We combine the $ϕp$ correlation function analysis and HAL QCD results in Model A. We assume the spin-spin interactions for $J/ψN$ and $ϕN$ systems are inversely proportional to their masses in Model B. Model A predicts a stronger $ϕN({}^2 S_{1/2})$ interaction and permits a two-body bound state, whereas Model B suggests the interaction is attractive but too weak to form a bound state. Both models predict bound states for the $I(J^P) = 0(0^-)$ and $0(1^-)$ $ϕNN$ systems. In Model A, these states are deeply bound with binding energies exceeding 15 MeV and remain existent when considering parameter uncertainties. In contrast, these states are very loosely bound in Model B, with binding energies below 1 MeV and an existent probability of about 60\% when parameter uncertainties are considered. In both models, there exist very loosely bound $I(J^P) = 0(2^-)$ three-body states which resemble a $ϕ$-d atom with the $ϕ$ meson surrounding the deuteron, but their existences are sensitive to parameter uncertainties. No bound states or resonances are found in the isovector $I(J^P) = 1(1^-)$ $ϕNN$ system.

hep-ph↗

arXiv2025

Electromagnetic polarizabilities of the spin-$\frac{1}{2}$ singly heavy baryons in heavy baryon chiral perturbation theory

We calculate the electromagnetic polarizabilities of the spin-$\frac{1}{2}$ singly heavy baryons in the heavy baryon chiral perturbation theory up to $\mathcal{O}(p^3)$. We estimate the low-energy constants using the magnetic moments of singly charmed baryons from lattice QCD simulations and the experimental decay widths of $Σ_c$ and $Σ_c^*$. Our results indicate that the long-range chiral corrections make significant contributions to the polarizabilities. Additionally, the magnetic dipole transitions $\mathcal{B}_6^* \to \mathcal{B}_6 +γ$ also provide large contribution to the magnetic polarizabilities.

hep-ph↗

arXiv2025

Trilepton and tetralepton bound and resonant states: the QED counterpart of multiquark states

This work presents the first prediction of tetralepton resonant states containing muons, extending beyond the simplest tetralepton system, dipositronium ($\mathrm{Ps}_2$). With the rapid advancements in experimental facilities, the production and study of these intriguing states may be within reach. We perform a comprehensive analysis of S-wave trilepton and tetralepton systems within the framework of a QED Coulomb potential. We employ the Gaussian expansion method to solve the three- or four-body Schrödinger equation and utilize the complex scaling method to identify resonant states. We uncover a series of bound and resonant states in the trilepton systems $e^+e^+e^-$, $μ^+μ^+μ^-$, $e^+e^+μ^-$, and $μ^+μ^+e^-$, as well as the tetralepton systems $e^+e^+e^-e^-$, $μ^+μ^+μ^-μ^-$, and $μ^+μ^+e^-e^-$. The energies of these states range from $-30$ eV to $-1$ eV below the total mass of three or four leptons, with their widths varying from less than $0.01$ eV to approximately $0.07$ eV. Additionally, we calculate the spin configurations and root mean square radii of these states, providing insight into their spatial structures. No bound or resonant states are found in the trilepton $e^+μ^+e^-$, $μ^+e^+μ^-$ systems, nor in the tetralepton $μ^+e^+μ^-e^-$ system. A comparison with fully heavy tetraquark systems reveals that the additional color degree of freedom in QCD results in the absence of low-energy bound and resonant states. However, this extra degree of freedom allows for a broader range of $J^{PC}$ quantum numbers to produce resonant states, highlighting the rich complexity of QCD systems.

hep-ph↗