arXiv subjects

Zhi-Feng Sun

Publications and source records attributed to Zhi-Feng Sun.

At least 19 recordsLinked to original sources

arXiv2025

Color gauge invariant theory of diquark interactions

In the present work, we construct a color gauge invariant theory of diquark interactions. With the transformation rule of the diquark fields and the definition of the covariant derivatives under color SU(3) symmetry, we construct the gauge invariant Lagrangians describing the vertices of $S-S-G$, $A-A-G$, $S_Q-S_Q-G$, $A_Q-A_Q-G$ and $S_Q-A_Q-G$, where $S_{(Q)}$ is the light (heavy) scalar diquark field, $A_{(Q)}$ is the light (heavy) axial vector diquark field, and $G$ is the gluon field. And then we derive the one-gluon-exchange effective potentials for diquark-antidiquark interactions using the obtained Lagrangians. By comparing these potentials with those in Godfrey-Isgur quark model, the coupling constants of the Lagrangians are determined. We find that the potentials are mainly made of Coulomb, contact and tensor terms. The potential for the process $S\bar{A}\to A\bar{S}$ is 0, since $\mathcal{L}_{SAG}=0$. And the tensor terms proportional to $g^2$ are negligible.

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arXiv2025

New Types of Hydrogenlike matter Composed of Electron(s) and Meson(s)

In the present work, we predict the existence of new types of hydrogenlike matter, including hydrogenlike atoms ($π^+e^-$, $K^+e^-$, $D^+e^-$), hydrogenlike molecular ions ($π^+π^+e^-$, $K^+K^+e^-$, $D^+D^+e^-$) and hydrogenlike molecules ($π^+π^+e^-e^-$, $K^+K^+e^-e^-$, $D^+D^+e^-e^-$). By solving the Schrödinger equation, the binding energy of hydrogenlike atoms is obtained as $E_n=-\frac{1}{2n^2}$. For hydrogenlike molecular ions and molecules, the variational method is employed to calculate the binding energies, i.e., $E_+=-0.587$ and $E_0=-1.139$ for hydrogenlike molecular ions and molecules, respectively. And the bond lengths for hydrogenlike molecular ions and molecules are also calculated, whose values are $2.003$ and $1.414$, respectively. Here all the quantities are in atomic units for convenience. In addition, the strong interaction between the two constituent mesons is considered in our calculations, where we find that its influence on the hydrogenlike molecular ions and molecules can be neglected. Comparisons of hydrogenlike molecular ion and molecule with the systems governed by the strong interaction are made, which suggests the possible existence of doubly heavy triquark, hidden heavy-flavor tetraquarks and doubly heavy tetraquarks. Hopefully, these types of matter would be observed in the future with the improvement of accuracy in the high energy physical experiments.

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arXiv2025

Spectroscopy and Decay Properties of Excited Charmonium States

In this work, we investigate the mass spectra of excited charmonia employing a nonrelativistic potential model with screening effect, and analyze their two-body strong decay, two-photon decay, leptonic decay, and hadronic transitions. Especially, we find that the newly observed resonances $X(4160)$, $Y(4500)$, and $Y(4710)$ can be identified as $3^3P_0$, $3^3D_1$, and $4^3D_1$ states, respectively. We also predict the masses and the widths of higher excited states in the charmonia family.

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arXiv2025

Study on the structure of the $Z_{c}(3900)$ state

In this work, we studied the $Z_{c}(3900)$ state within the framework of effective field theory. We firstly show the construction of the Lagrangian describing meson-meson-meson and meson-diquark-diquark interactions. By using the Feynman rule, we calculate the effective potentials corresponding to the coupled channels of $D\bar{D}^{*}/D^{*}\bar{D}$ and $S_{cq}\bar{A}_{cq}/A_{cq}\bar{S}_{cq}$ with $S_{cq}$ ($A_{cq}$) the scalar (axial vector) diquark composed of $c$ and $q$ quarks. After solving the Bethe-Salpeter equation of the on-shell parametrized form and compare our numerical results with the experimental mass and width of $Z_{c}(3900)$, we find that the $Z_{c}(3900)$ state can be explained as the mixture of $D\bar{D}^{*}/D^{*}\bar{D}$ and $S_{cq}\bar{A}_{cq}/A_{cq}\bar{S}_{cq}$ components.

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arXiv2024

One or two poles for the $Ξ(1820)$?

In this talk, we present a new interpretation for the recently observed $Ξ(1820)$ resonance. We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the $Ξ(1820)$ resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the $K^- Λ$ mass distribution in the $ψ(3686)$ decay to $K^- Λ\barΞ^+ $, which demands a width much larger than the average of the PDG, and show how the consideration of the two $Ξ(1820)$ states provides a natural explanation to this apparent contradiction.

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arXiv2024

The $X(4500)$ state considered as the mixture of hadronic molecule and diquark-antidiquark within effective field theory

In the present work, we construct the Lagrangians including three-meson, meson-diquark-antidiquark vertices, such that the diquark-antidiquark component as well as the molecular component are introduced within the effective field theory. With the obtained effective potentials projecting to spin 0, 1 and 2, we solve the Bethe-Salpeter equation with the on-shell approximation, and find that $X(4500)$ can be explained as the mixture of components $D_{s}^{*+}D_{s}^{*-}$, ${A}_{cq}\bar{A}_{cq}$ and ${A}_{cs}\bar{A}_{cs}$ with $I^G(J^{PC})=0^+(0^{++})$. In addition, another two resonances with quantum numbers $I^G(J^{PC})=0^+(1^{++})$ and $I^G(J^{PC})=0^+(2^{++})$ are predicted.

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arXiv2024

Possible molecules of triple-heavy pentaquarks within the extended local hidden gauge formalism

In this study, we explore the interactions between mesons and baryons in the open heavy sectors to identify potential triple-heavy molecular pentaquarks. We derive the meson-baryon interaction potentials using the vector meson exchange mechanism within the extended local hidden gauge formalism. The scattering amplitudes are computed by solving the coupled-channel Bethe-Salpeter equation, revealing several bound systems. By analyzing the poles of these amplitudes in the complex plane, we determine the masses and widths of these bound states. Additionally, we evaluate the couplings and compositeness of different channels within each bound system to assess their molecular characteristics. Our predictions include four $Ω_{ccc}$-like states, four $Ω_{bbb}$-like states, fourteen $Ω_{bcc}$-like states, and ten $Ω_{bbc}$-like states, which could be targets for future experimental investigations.

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arXiv2024

Isospin violation effect and three-body decays of the $T_{cc}^{+}$ state

In this work, we make a study of $T_{cc}^+$ state observed by the LHCb collaboration in 2021. In obtaining the effective potentials using the One-Boson-Exchange Potential Model we use an exponential form factor, and find that in the short and medium range, the contributions of the $π$, $ρ$ and $ω$ exchanges are comparable while in the long range the pion-exchange contribution is dominant. Based on the assumption that $T_{cc}^+$ is a loosely bound state of $D^*D$, we focus on its three-body decay using the meson-exchange method. Considering that the difference between the thresholds of $D^{*+}D^0$ and $D^{*0}D^+$ is even larger than the binding energy of $T_{cc}^+$, the isospin-breaking effect is amplified by the small binding energy of $T_{cc}^+$. Explicitly including such an isospin-breaking effect we obtain, by solving the Schrödinger equation, that the probability of the isoscalar component is about $91\%$ while that of the isovector component is around $9\%$ for $T_{cc}^+$. Using the experimental value of the mass of $T_{cc}^+$ as an input, we obtain the wave function of $T_{cc}^+$ and further obtain its width via the three-body hadronic as well as the radiative decays. The total width we obtain is in agreement with the experimental value of the LHCb measurement with a unitarised Breit-Wigner profile. Conversely, the current results support the conclusion that $T_{cc}^+$ is a hadronic molecule of $D^*D$.

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arXiv2024

The $Z_b$ states as the mixture of the molecular and diquark-anti-diquark components within the effective field theory

In this study, we reconsider the states $Z_b(10610)$ and $Z_b(10650)$ by investigating the presence of diquark-anti-diquark components as well as the hadronic molecule components in the framework of effective field theory. The different masses of pseudoscalar mesons such as $π^{0}$, $η_{8}$, and $η_{0}$, as well as vector mesons like $ρ^{0}$ and $ω$ violate the OZI rule that is well depicted under the $[U(3)_L\otimes U(3)_R]_{global}\otimes [U(3)_V]_{local}$ symmetry. To account for the contribution of intermediate bosons of heavy masses within the OBE model, we introduce an exponential form factor instead of the commonly used monopole form factor in the past. By solving the coupled-channel Schrödinger equation with the Gaussian expansion method, our numerical results indicate that the $Z_b(10610)$ and $Z_b(10650)$ states can be explained as hadronic molecules slightly mixing with diquark-anti-diquark states.

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arXiv2024

Molecular-type $QQss\bar{s}$ pentaquarks predicted by an extended hidden gauge symmetry approach

In this work, we investigate the double-heavy molecular pentaquark states with the quark contents $ccss\bar{s}$, $bbss\bar{s}$, and $bcss\bar{s}$ by using the coupled channel approach. The extended local hidden gauge Lagrangians are used to obtain the meson-baryon interactions by exchanging the vector mesons. We predict some candidates for the molecular states with the quantum numbers $I(J^{P}) = 0(1/2^{-}, 3/2^{-}, 5/2^{-})$, whose binding energies are of the order of $20-30$ MeV and whose widths are all less than $8$ MeV. These predicted exotic double-heavy molecular pentaquark states may be accessible in future experiments such as LHCb.

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arXiv2023

Two states for the $Ξ(1820)$ resonance

We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the $Ξ(1820)$ resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the $K^- Λ$ mass distribution in the $ψ(3686)$ decay to $K^- Λ\barΞ^+ $, which demands a width much larger than the average of the PDG, and show how the consideration of the two $Ξ(1820)$ states provides a natural explanation to this apparent contradiction.

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arXiv2023

The hidden strange $B_{c}$-like molecular states

With the chiral unitary approach, we evaluate the hidden strange $B_{c}$-like molecular states of $b\bar{c}s\bar{s}$ systems $\bar{B}_{s}\bar{D}_{s}$, $\bar{B}_{s}^{*}\bar{D}_{s}$, $\bar{B}_{s}\bar{D}_{s}^{*}$, and $\bar{B}_{s}^{*}\bar{D}_{s}^{*}$ coupled to the non-strange channels. The $S$-wave scattering amplitudes are calculated based on the vector meson exchange, four pseudoscalar mesons contact interactions, and four vector mesons contact interactions obtained from the extended local hidden gauge approach. We find six states below the threshold of the most relevant channel. The binding energies of these states are around $1-10$ MeV and the widths are around $0.2-0.7$ MeV. Our research is a supplement to the mass spectra of $B_{c}$-like states, which may be useful for the experimental search in the future.

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arXiv2022

Study of the resonance contributions in the $Ξ_{b}^{-} \rightarrow pK^{-}K^{-}$ decay

The decay process $Ξ_{b}^{-} \rightarrow pK^{-}K^{-}$ is studied with the final state interaction approach by considering the contributions from the $S$-wave meson-baryon interactions, and also the intermediate state $Λ(1520)$ in the $D$-wave. The low-lying resonances $Λ(1405)$ and $Λ(1670)$ have significant contributions, which are both dynamically generated from the $S$-wave final state interactions with isospin $I=0$. Furthermore, the $Λ(1520)$ state also has important contributions from $D$-wave. With these resonances contributions, the experimental data of the lower $pK^{-}$ invariant mass distributions are well described. We also discuss the contribution of another resonance in the $S$-wave with isospoin $I=1$, which cannot be ignored. Moreover, some of the branching fractions obtained for the corresponding decay channels are consistent with the experimental measurements.

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arXiv2022

The $Z_{cs}$ states and the mixture of hadronic molecule and diquark-anti-diquark components within effective field theory

In this work, we construct the Lagrangian describing meson-diquark interaction, such that the diquark-anti-diquark component as well as the molecular component is introduced when studying the $Z_{cs}$ states. In this way, the problem is solved that if only considering the $\bar{D}^{(*)}D_s^{(*)}$ components, the potentials are suppressed by OZI rule. Through solving the Bethe-Salpeter equation, we find that the $Z_{cs}(4000)^+$ can be explained as the mixture of $\bar{D}^{*0}D_s^+$ and $\bar{A}_{cs}S_{cu}$ components. Besides, for the $\bar{D}^{*0}D_s^{*+}/\bar{A}_{cs}A_{cu}$ system, the pole of $4208\pm 13i$ MeV on the second Riemann sheet is predicted, whose mass agrees with that of $Z_{cs}(4220)^+$ while the width is much smaller than $Z_{cs}(4220)^+$. Due to the large error of the $Z_{cs}(4220)^+$'s width, further measurements are expected. In addition, several other poles of different spins are predicted.

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arXiv2021

Magnetic moments and transition magnetic moments of $P_c$ and $P_{cs}$ states

We study the magnetic moments and transition magnetic moments of $P_c$ and $P_{cs}$ states in the molecular picture. We first revisit the magnetic moments of $P_c$ states as the $S$ wave molecular states without coupled channel effects. The coupled channel effects and the $D$ wave contributions are then investigated carefully. The coupled channel effects contribute to the change of $0.1\sim 0.4$ nuclear magneton $μ_N$ for most cases while the $D$ wave only induces the variation of less than $0.03 ~μ_N$. In addition, we obtain the transition magnetic moments between different $P_c$ states and the related electromagnetic decay widths of $P_c'\to P_cγ$. The magnetic moments of $P_{cs}$ are much different for the assumption of spin being 1/2 and 3/2. The study of electromagnetic properties will help us disclose further the structure of these unconventional states.

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arXiv2021

Study of $D_{s}^{+} \rightarrow K^{+} K^{-} π^{+}$ decay

We investigate the $D_{s}^{+} \rightarrow K^{+} K^{-} π^{+}$ decay theoretically with the final state interactions, which is based on the chiral unitary approach and takes into account the external and internal $W$-emission mechanisms at the quark level. Only considering three resonances contributions, the $f_0(980)$ in $S$-wave, the $\bar {K}^{*}(892)^{0}$ and $ϕ(1020)$ in $P$-wave, one can make a good description of the recent experimental data from BESIII Collaboration, where the contribution from $S$-wave is found to be small. Besides, we also make a calculation of the corresponding branching fractions, which are consistent with the results of BESIII Collaboration and Particle Data Group.

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arXiv2021

Perfect $DD^*$ molecular prediction matching the $T_{cc}$ observation at LHCb

In 2012, we investigated the possible molecular states composed of two charmed mesons [Phys.Rev. D 88, 114008 (2013), arXiv:1211.5007 [hep-ph](2012)]. The $D^*D$ system with the quantum numbers of $I(J^P)=0(1^+)$ was found to be a good candidate of the loosely bound molecular state. This state is very close to the $D^*D$ threshold with a binding energy around 0.47 MeV. This prediction was confirmed by the new LHCb observation of $T_{cc}^+$ [see Franz Muheim's talk at the European Physical Society conference on high energy physics 2021].

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arXiv2021

Doubly charmed molecular pentaquarks

We perform a systematic exploration of the possible doubly charmed molecular pentaquarks composed of $Σ_c^{(*)}D^{(*)}$ with the one-boson-exchange potential model. After taking into account the $S-D$ wave mixing and the coupled channel effects, we predict several possible doubly charmed molecular pentaquarks, which include the $Σ_cD$ with $I(J^P) = 1/2(1/2^-)$, $Σ_c^*D$ with $1/2(3/2^-)$, and $Σ_cD^*$ with $1/2(1/2^-)$, $1/2(3/2^-)$. The $Σ_cD$ state with $3/2(1/2^-)$ and $Σ_cD^*$ state with $3/2(1/2^-)$ may also be suggested as candidates of doubly charmed molecular pentaquarks. The $Σ_cD$ and $Σ_c^*D$ states can be searched for by analyzing the $Λ_cDπ$ invariant mass spectrum of the bottom baryon and $B$ meson decays. The $Σ_cD^*$ states can be searched for in the invariant mass spectrum of $Λ_cD^*π$, $Λ_cDππ$ and $Λ_cDπγ$. Since the width of $Σ_c^*$ is much larger than that of $D^*$, $Σ_c^*D\rightarrow Λ_cDπ$ will be the dominant decay mode. We sincerely hope these candidates for the doubly charmed molecular pentaqurks will be searched by LHCb or BelleII collaboration in the near future.

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