arXiv subjects

Zhan-Wei Liu

Publications and source records attributed to Zhan-Wei Liu.

At least 19 recordsLinked to original sources

arXiv2026

Scattering of $Λ_{c}Λ_{c}$ and $Λ_{c}\barΛ_{c}$ in chiral effective field theory

We investigate the $S$-wave scatterings of $Λ_cΛ_c$ and $Λ_{c}\bar Λ_{c}$ systems within a unified chiral effective field theory framework up to next-to-leading order. The contact low-energy coupling constants are determined by fitting to the lattice QCD results for the $Λ_cΛ_c$ scattering phase shift at an unphysical pion mass. After extrapolating to the physical pion mass, we find a repulsive interaction in the $I(J^P)=0(0^{+})$ $Λ_cΛ_c$ channel, consistent with the lattice QCD simulation. On the $Λ_{c}\bar Λ_{c}$ side, using the fitted contact low-energy constants, we predict the phase shifts and potentials for $Λ_c \barΛ_c$ scattering in the $I(J^{PC})=0(0^{-+})$ and $0(1^{--})$ channels. Attractive interactions are found in both channels, each allowing for the formation of bound states. In particular, the attraction in the $0(1^{--})$ $Λ_c \barΛ_c$ channel is stronger. In addition, our analysis reveals that the spin-spin term caused by the two-pion exchange contributes significantly to the interactions, leading to a distinct mass splitting between the $0(0^{-+})$ and $0(1^{--})$ $Λ_c \barΛ_c$ channels.

hep-ph↗

arXiv2026

Two-Pole Structure of $Λ(1405)$ with Temporal Evolution and Spatial Distribution

The $Λ(1405)$ is a special hadron resonance associated with two poles of the scattering amplitudes, and its nature remains under debate since its discovery before the birth of the quark model. In this work we study the structures of these two poles and their temporal evolution, including their difference, interference, and synergy. Each pole can usually be represented by the Gamow vector $|ψ^{\rm Gamow}\rangle$ in the complex momentum space $|\vec p e^{-iθ}\rangle$. We construct its representation $|ψ^{\rm phys}\rangle$ in the real momentum space $|\vec p\rangle$ through the analytic continuation of the Gamow wavefunction, which also satisfies the Hamiltonian eigenvalue equation with the assistance of a virtual state vector. Both the decreasing behavior of the resonance and the production of the decayed scattering states can be simultaneously described by the temporal evolution $|ψ^{\rm phys},t\rangle=\exp(-iH t) \, |ψ^{\rm phys}\rangle$. The state $|ψ^{\rm phys},t=0\rangle$ gives the finite-range confinement of the resonance while $|ψ^{\rm phys},t\to \infty\rangle$ provides a Breit-Wigner-like distribution of the final scattering states whose appearance probability is nonzero as $r\to \infty$. In the two-channel system $πΣ$-$\bar{K}N$, we first dynamically generate the two poles of $Λ(1405)$ and then discuss their temporal evolutions and spatial distributions which can produce results consistent with experimental measurements such as the $πΣ$ invariant-mass spectrum and provide a new path to study hadron resonances.

hep-ph↗

arXiv2026

Classical and spin polarizabilities of singly heavy baryons within heavy baryon chiral perturbation theory

We present a systematic study of the electromagnetic and spin polarizabilities of spin-1/2 singly charmed baryons at $\mathcal{O}(p^4)$ within the framework of heavy baryon chiral perturbation theory. Our results show that the higher-order corrections to the electric polarizability are small, while those to the magnetic polarizability are relatively larger due to the small mass splitting of singly charmed baryons and are closely related to transition magnetic moments. Furthermore, we find that the spin polarizabilities of singly charmed baryons, except for $γ_{M1M1}$, are much smaller than those of the nucleons. We have also calculated the polarizabilities for singly bottom baryons, with the results showing generally larger values than those of singly charmed baryons.

hep-ph↗

arXiv2026

Lattice QCD constraints on pion electroproduction off a nucleon

Very recently, a lattice QCD collaboration has explored threshold pion electroproduction near the physical pion mass and has simulated the relevant multipole amplitudes. Different multipole amplitudes are usually entangled in experimental data, and thus extracting each of them independently from first principles provides additional essential constraints on phenomenological theories. We use nonperturbative Hamiltonian theory to investigate the electroproduction process, providing an advanced approach with additional two-particle coupled channels to acquire the physical electric dipole amplitudes from the original lattice QCD data. We note that future lattice QCD simulations of the electric dipole amplitudes at higher energies will be much closer to their physical counterparts than the current ones near threshold. In addition, we obtain a new expression which, like that of Lellouch-Lüscher, depends only on the final-state interactions but provides both the real and imaginary parts of the transition amplitudes.

hep-ph↗

arXiv2026

The odd-parity strange baryons $Σ\,(\frac{1}{2}^-)$ below 1.8 GeV with Hamiltonian effective field theory

We examine the spectrum of the $Σ\,(\frac{1}{2}^-)$ family based on the experimental $K^-p$ scattering data and lattice QCD simulations within the Hamiltonian Effective Field Theory. Especially, two different scenarios are constructed in order to clarify whether there is one or two $Σ\,(\frac{1}{2}^-)$ resonances with masses around 1.5$\sim$1.7 GeV. The relevant lattice QCD data support our scenario with two resonance poles at $1687-110\,i$ and $1714-14\,i$ MeV in which the bare strange triquark core plays an important role. We also show an extra clear cusp structure around 1.4 GeV in our scattering T matrices associated with the odd-parity strange baryons.

hep-ph↗

arXiv2025

Pion photoproduction of nucleon excited states with Hamiltonian effective field theory

Over the past few years, Hamiltonian effective field theory has been successfully applied to studies of nucleon and hyperon excited states. By discretizing the Hamiltonian in a finite volume, one can obtain the energy spectrum and compare it with the results calculated from lattice QCD. Through the analysis of experimental data, Hamiltonian effective field theory provides a framework that connects the finite-volume spectra from lattice QCD to infinite-volume scattering observables. The model independence of the approach is well preserved under the combined constraints from lattice QCD and experimental data. Building on these developments, recent works have attempted to extend HEFT to electromagnetic processes. Meanwhile, lattice QCD has also gradually advanced into the study of electromagnetic interactions. The combination of these analyses will undoubtedly deepen our understanding of light resonances.

hep-ph↗

arXiv2025

Structure of the $Ω^{-}(2012)$ with Hamiltonian Effective Field Theory

We investigate the internal structure of the $Ω(2012)^-$ by analyzing lattice QCD simulation and experimental data within Hamiltonian effective field theory, considering both $J^P = 1/2^-$ and $3/2^-$ assignments. The couplings to the dominant decay channel $Ξ\bar{K}$ and the near-threshold channel $Ξ(1530) \bar{K}$ are determined through the quark-pair-creation model. By studying the lattice QCD spectra in these two spin-parity scenarios, we extract the masses and widths of the resonances. We notice that the $J^P = 3/2^-$ resonance is consistent with the observed $Ω(2012)^-$ while the recently reported $Ω(2109)^-$ may be a $J^P = 1/2^-$ $Ω$.

hep-ph↗

arXiv2025

Chiral extrapolation of the doubly charmed baryons magnetic properties

The magnetic moments, magnetic form factors, and transition magnetic form factors of doubly charmed baryons are studied within heavy baryon chiral perturbation theory. We regulate the loop integrals using the finite-range regularization. The contributions of vector mesons are taken into account to investigate the dependence of form factors on the transferred momentum. The finite volume and lattice spacing effects are considered to analyze the lattice QCD simulations which can be understood well in our framework.

hep-ph↗

arXiv2024

Masses and radiative decay widths of the $D_{s0}^*(2317)$ and $D_{s1}^{\prime}(2460)$ and their bottom analogs

We study the mass spectra and radiative decays of $D_{s0}^*(2317)$ and $D_{s1}^{\prime}(2460)$ in an unquenched framework. In addition to coupled channel effects between the $c\bar{s}$ cores and $D^{(*)}K$ channels, $D^{(*)}K$-$D^{(*)}K$ self interactions are also considered in this work and we succeed to reproduce their mass spectra. Furthermore, we study the radiative decays of the $D_{s0}^*(2317)$ and $D_{s1}^{\prime}(2460)$ by simultaneously including the compound structures of conventional $c\bar{s}$ cores and $D^{(*)}K$ components. We also calculate their bottom analogs with heavy quark symmetry. Our study offers useful insights into the important unquenched effects in the formation of $D_{s0}^*(2317)$, $D_{s1}^{\prime}(2460)$ and the bottom counterparts.

hep-ph↗

arXiv2024

Pion photoproduction of nucleon excited states with Hamiltonian effective field theory

We refine our previous calculation of multipole amplitude $E_{0+}$ for pion photoproduction process, $γN\rightarrowπN$. The treatment of final-state interactions is based upon an earlier analysis of pion-nucleon scattering within Hamiltonian effective field theory, supplemented by incorporating contributions from the $N^*(1650)$ and the $KΛ$ coupled channel. The contribution from the bare state corresponding to the $N^*(1650)$ significantly enhances our results. Additionally, we also compute the multipole amplitude $M_{1-}$, which is of direct relevance to the Roper resonance. The results are comparable with other dynamical coupled channel models, even though the contribution from the bare state (interpreted as a 2$s$ excitation) in this channel is small because of its large mass.

hep-ph↗

arXiv2024

The role of electromagnetic interaction in the $X(3872)$ and its analogs

We investigate the role of the electromagnetic interaction in the formation and decay of the $X(3872)$. The binding properties of the $X(3872)$ are studied by assuming the molecular nature and considering the $S$-$D$ wave mixing, isospin breaking, and coupled channel effects, and in particular the correction from the electromagnetic interaction. The radiative decays can better reflect the difference between the charged and neutral $D\bar D^*$ components, since the electromagnetic interaction explicitly breaks the isospin symmetry. We further study the radiative decay widths with the obtained wave functions for different $D\bar D^*$ channels. We also explore other similar hidden-charm molecular states. The electromagnetic interaction can make the molecule tighter. Our result of the radiative decay width for $X(3872)\rightarrow γJ/ψ$ is in agreement with the experiment. The branching ratio $R_{γψ}$ is less than 1 in our framework, which supports the Belle and BESIII measurements.

hep-ph↗

arXiv2024

Structure of the $\mathbf{Λ(1670)}$ resonance

We examine the internal structure of the $Λ(1670)$ through an analysis of lattice QCD simulations and experimental data within Hamiltonian effective field theory. Two scenarios are presented. The first describes the $Λ(1670)$ as a bare three-quark basis state, which mixes with the $πΣ$, $\bar{K}N$, $ηΛ$ and $KΞ$ meson-baryon channels. In the second scenario, the $Λ(1670)$ is dynamically generated from these isospin-0 coupled channels. The $K^-p$ scattering data and the pole structures of the $Λ(1405)$ and the $Λ(1670)$ can be simultaneously described well in both scenarios. However, a comparison of the finite-volume spectra to lattice QCD calculations reveals significant differences between these scenarios, with a clear preference for the first case. Thus the lattice QCD results play a crucial role in allowing us to distinguish between these two scenarios for the internal structure of the $Λ(1670)$.

hep-ph↗

arXiv2024

Understanding the nature of baryon resonances

This presentation opens with a brief review of lattice QCD calculations showing the $2s$ radial excitation of the nucleon sits at approximately 2 GeV, well above the Roper resonance position. We then proceed to reconcile this observation with experimental scattering data. While the idea of dressing quark-model states in a coupled-channel analysis to describe scattering data has been around for decades, it's now possible to bring these descriptions to the finite-volume of lattice QCD for confrontation with lattice-QCD calculations. This combination of lattice QCD and experiment demands that we reconsider our preconceived notions about the quark-model and its excitation spectrum. We close with a discussion of an unanticipated resolution to the missing baryon resonances problem.

hep-lat↗

arXiv2023

Spectroscopy behavior of fully heavy tetraquarks

Stimulated by the observation of the $X(6900)$ from LHCb in 2020 and the recent results from CMS and ATLAS in the di-$J/ψ$ invariant mass spectrum, in this work we systemically study all possible configurations for the ground fully heavy tetraquark states in constituent quark model. By our calculation, we present their spectroscopy behaviors like binding energy, lowest meson-meson thresholds, specific wave function, magnetic moment, transition magnetic moment, radiative decay width, rearrangement strong width ratio, internal mass contributions, relative lengths between (anti)quarks, and the spatial distribution of four valence (anti)quarks. We cannot find stable S-wave state for the fully heavy tetraquark system. We hope that our results are valuable to further explore fully heavy tetraquark states in experiment.

hep-ph↗

arXiv2023

Exploring the electromagnetic properties of the $Ξ_c^{(\prime,\,)} \bar D_s^$ and $Ω_c^{()} \bar D_s^$ molecular states

This paper presents a systematic investigation of the electromagnetic properties of the hidden-charm molecular pentaquarks within the constituent quark model. Specifically, it focuses on two types of pentaquarks: the $Ξ_c^{(\prime,*)} \bar{D}_s^{*}$-type pentaquarks with double strangeness and the $Ω_{c}^{(*)}\bar D_s^{*}$-type pentaquarks with triple strangeness. The study explores various electromagnetic properties, including the magnetic moments, the transition magnetic moments, and the radiative decay behavior of these pentaquarks. To ensure realistic calculations, the $S$-$D$ wave mixing effect and the coupled channel effect are taken into account. By examining the electromagnetic properties of the hidden-charm molecular pentaquarks with double and triple strangeness, this research contributes to the deeper understanding of their spectroscopic behavior. These findings form a valuable addition to the ongoing investigation into the broader spectrum of properties exhibited by the hidden-charm molecular pentaquarks.

hep-ph↗

arXiv2023

Low-lying odd-parity nucleon resonances as quark-model like states

Recent lattice QCD results for the low-lying odd-parity excitations of the nucleon near the $N^{*}(1535)$ and $N^{*}(1650)$ resonance positions have revealed that the lattice QCD states have magnetic moments consistent with predictions from a constituent-quark-model. Using Hamiltonian Effective Field Theory (HEFT) to describe pion-nucleon scattering in the $I(J^{P}) = \frac{1}{2}(\frac{1}{2}^{-})$ channel, we represent these two quark-model like states as two single-particle bare basis states, dressed and mixed by meson-baryon scattering channels. By constraining the free parameters of the Hamiltonian with $S_{11}$ pion-nucleon scattering data, we perform the first calculation of the finite-volume spectrum using two bare-baryon basis states. By comparing this spectrum to contemporary lattice QCD results at three lattice volumes, we analyse the eigenvectors of the Hamiltonian to gain insight into the structure and composition of these two low-lying resonances. We find that an interpretation of the two low-lying nucleon resonances as quark-model like states dressed by meson-baryon interactions is consistent with both the $S_{11}$ scattering data and lattice QCD. We introduce a novel HEFT formalism for estimating scattering-state contaminations in lattice QCD correlation functions constructed with standard three-quark operators. Not only are historical lattice QCD results described with excellent accuracy, but correlation functions with large scattering-state contaminations are identified.

hep-lat↗

arXiv2023

Doubly charmed dibaryon states

In this work, we study the doubly charmed dibaryon states with the $qqqqcc$ ($q =u, d, s$) configuration. The mass spectra of doubly charmed dibaryon states are obtained systematically within the chromomagnetic interaction model. In addition to the mass spectrum analysis, we illustrate their two-body strong decay behaviours. Our results suggest that there may be narrow states or even stable states that cannot decay through the strong interaction. We hope that our results will provide valuable information for further experimental searches for doubly charmed dibaryon states.

hep-ph↗

arXiv2023

Toy model to understand oscillatory behavior in timelike nucleon form factors

To understand the oscillatory behavior exhibited in the timelike electromagnetic form factors of nucleons, we propose a toy model based on the Jost function of the $N\bar N$ pair into the timelike form factors with the help of the distorted-wave Born approximation. By constructing a simple square-well potential reflecting the final-state interaction of $N\bar N$, we naturally represent the damped oscillatory phenomenon in the timelike electromagnetic form factors of nucleons. Especially, our study reveals that the ``period" of the oscillation is approximately determined by the Yukawa interaction range $1/m_π$. Other possible potentials are also discussed. The threshold enhancements of the cross sections for $e^+e^-\to n\bar n$, $Λ\barΛ$, and $Λ_c\barΛ_c$ can also be understand within this scenario.

nucl-th↗