In this paper, we tentatively assign the $P_{c}(4312)$ to be a $\bar{D}Σ_{c}$ molecular state with quantum number $J^{P}=\frac{1}{2}^{-}$, and calculate its magnetic moment using the QCD sum rule method in external weak electromagnetic field. Starting with the two-point correlation function in external electromagnetic field and expanding it in power of the electromagnetic interaction Hamiltonian, we extract the magnetic moment from the linear response to the external electromagnetic field. The numerical value of the magnetic moment of $P_{c}(4312)$ is $μ_{P_{c}}=1.75^{+0.15}_{-0.11}$.
Masses for $\{Q\bar{q}\}\{\bar{Q}^{(')}q\}$ molecular states are systematically studied in QCD sum rules. The interpolating currents representing the related molecular states are proposed. Technically, contributions of the operators up to dimension six are included in operator product expansion (OPE). Mass spectra for molecular states with $\{Q\bar{q}\}\{\bar{Q}^{(')}q\}$ configurations are obtained.
We systematically investigate the mass spectra of $\{Q\bar{s}\}\{\bar{Q}^{(')}s\}$ molecular states in the framework of QCD sum rules. The interpolating currents representing the molecular states are proposed. Technically, contributions of the operators up to dimension six are included in operator product expansion (OPE). The masses for molecular states with various $\{Q\bar{s}\}\{\bar{Q}^{(')}s\}$ configurations are presented. The result $4.36\pm0.08 GeV$ for the $D_{s}^{*}\bar{D}_{s0}^{*}$ molecular state is consistent with the mass $4350^{+4.6}_{-5.1}\pm0.7 MeV$ of the newly observed $X(435…
In this article, we study the $\bar{D}Σ_c$, $\bar{D}Σ_c^*$, $\bar{D}^{*}Σ_c$ and $\bar{D}^{*}Σ_c^*$ pentaquark molecular states with the QCD sum rules by carrying out the operator product expansion up to the vacuum condensates of dimension $13$ in a consistent way. The present calculations support assigning the $P_c(4312)$ to be the $\bar{D}Σ_c$ pentaquark molecular state with $J^P={\frac{1}{2}}^-$, assigning the $P_c(4380)$ to be the $\bar{D}Σ_c^*$ pentaquark molecular state with $J^P={\frac{3}{2}}^-$, assigning the $P_c(4440/4457)$ to be the $\bar{D}^{*}Σ_c$ pentaquark molecular state with $…
Masses for the $(Q\bar{s})^{(*)}(\bar{Q}s)^{(*)}$ ($Q=c$ or $b$) molecular states are systematically computed in the framework of QCD sum rules. Technically, contributions of the operators up to dimension six are included in operator product expansion (OPE). The numerical result $4.13\pm0.10 {GeV}$ for $D_{s}^{*}\bar{D}_{s}^{*}$ agrees well with the mass $4143.0\pm2.9\pm1.2 {MeV}$ for Y(4140), which supports the $D_{s}^{*}\bar{D}_{s}^{*}$ molecular configuration for Y(4140).
In the present work, we construct the color-singlet-color-singlet type four-quark currents to investigate the $D_s\bar{D}_{s1}$ and $D_s^*\bar{D}_{s0}^*$ tetraquark molecular states with the $J^{PC}=1^{--}$ and $1^{-+}$ via the QCD sum rules, and obtain satisfactory results. We can search for the $D_s\bar{D}_{s1}$ and $D_s^*\bar{D}_{s0}^*$ tetraquark molecular states with the $J^{PC}=1^{--}$ and $1^{-+}$ at the BESIII and Belle II in the future.
In this work, we perform a dynamical study of the $B^{(*)}$ and $\bar K$ interaction and show that the newly reported $X(5568)$ or $X(5616)$ cannot be assigned to be an isovector $B\bar{K}$ or $B^*\bar{K}$ molecular state. We continue to investigate the isoscalar $B^{(*)}\bar{K}$ systems, and the $B^{(*)}\bar{K}$ systems with isospin $I=0,1$, and predict the existence of several isoscalar $B^{(*)}\bar K^{(*)}$ molecular states. A new task of exploring open-bottom molecular states will be created for future experiments.
In this talk, we firstly overview the experimental status of $\bar{N}_X(1625)$, which is an enhancement structure observed in $K^{-}\barΛ$ invariant mass spectrum of $J/ψ\to pK^{-}\barΛ$ process. Then we present the result of the decay of $\bar{N}_X(1625)$ under the two molecular assumptions, i.e. S-wave $\barΛK^-$ and S-wave $\barΣ^0K^-$ molecular states. Several experimental suggestions for $\bar{N}_X(1625)$ are proposed.
In this article, we assume that there exist scalar ${D}^\ast {\bar {D}}^\ast$, ${D}_s^\ast {\bar {D}}_s^\ast$, ${B}^\ast {\bar {B}}^\ast$ and ${B}_s^\ast {\bar {B}}_s^\ast$ molecular states, and study their masses using the QCD sum rules. The numerical results indicate that the masses are about $(250-500) \rm{MeV}$ above the corresponding ${D}^\ast -{\bar {D}}^\ast$, ${D}_s^\ast -{\bar {D}}_s^\ast$, ${B}^\ast -{\bar {B}}^\ast$ and ${B}_s^\ast -{\bar {B}}_s^\ast$ thresholds, the Y(4140) is unlikely a scalar ${D}_s^\ast {\bar {D}}_s^\ast$ molecular state. The scalar $D^\ast {\bar D}^\ast$, $D_s^…
Stimulated by the observations of recent observation of $Ω_c$ as well as former one of $P_c(4380)$ and $P_c(4450)$, we perform a coupled channel analysis of $Ξ_c^*\bar{K}/Ω_cη/Ω_c^*η/Ξ_c\bar{K}^*/Ξ_c'\bar{K}^*/Ω_cω$ systems to search for possible $Ω_c-$like molecular states by using a one-boson-exchange potential. Our results suggest there exists a loosely bound molecular state, a $Ξ_c^*\bar{K}/Ω_cη/Ω_c^*η/Ξ_c\bar{K}^*/Ξ_c'\bar{K}^*/Ω_cω$ with $I(J^P)=0(3/2^-)$, it is mainly composed of the $Ξ_c^*\bar{K}$ system. Two-body strong decay width is also studied, where we find that $Ξ_c'\bar{K}$ is …
The newly observed $Ξ(1620)^0$ by the Belle Collaboration inspires our interest in performing a systematic study on the interaction of an anti-strange meson $(\bar{K}^{(*)})$ with a strange or doubly strange ground octet baryon $\mathcal{B}$ ($Λ$, $Σ$, and $Ξ$), where the spin-orbit force and the recoil correction are considered in the adopted one-boson-exchange model. Our results indicate that $Ξ(1620)^0$ can be explained as a $\bar{K}Λ$ molecular state with $I(J^P)=1/2(1/2^-)$ and the intermediate force from $σ$ exchange plays an important role. Additionally, we also predict several other po…
In this work, we preform a systematic investigation about hidden heavy and doubly heavy molecular states from the $D^{(*)}\bar{D}^{(*)}/B^{(*)}\bar{B}^{(*)}$ and $D^{(*)}D^{(*)}/\bar{B}^{(*)}\bar{B}^{(*)}$ interactions in the quasipotential Bethe-Salpeter equation (qBSE) approach. With the help of Lagrangians with heavy quark and chiral symmetries, interaction potentials are constructed within the one-boson-exchange model in which we include the $π$, $η$, $ρ$, $ω$ and $σ$ exchanges, as well as $J/ψ$ or $Υ$ exchange. Possible bound states from the interactions considered are searched for as the…
We study the $B_c^- \to π^- J/ψω$ and $B_c^- \to π^- D^* \bar{D}^*$ reactions and show that they are related by the presence of two resonances, the $X(3940)$ and $X(3930)$, that are of molecular nature and couple most strongly to $D^* \bar{D}^*$, but also to $J/ψω$. Because of that, in the $J/ψω$ mass distribution we find a cusp with large strength at the $D^* \bar{D}^*$ threshold and predict the ratio of strengths between the peak of the cusp and the maximum of the $D^* \bar{D}^*$ distribution close to $D^* \bar{D}^*$ threshold, which are distinct features of the molecular nature of these two…
In this work, we tentatively identify the $P_{cs}(4338)$ as the $\bar{D}Ξ_c$ molecular state, and distinguish the isospins of the current operators to explore the $\bar{D}Ξ_c$, $\bar{D}Λ_c$, $\bar{D}_sΞ_c$, $\bar{D}_sΛ_c$, $\bar{D}^*Ξ_c$, $\bar{D}^*Λ_c$, $\bar{D}^*_sΞ_c$ and $\bar{D}^*_sΛ_c$ molecular states without strange, with strange and with double strange in the framework of the QCD sum rules in details. The present explorations favor identifying the $P_{cs}(4338)$ ($P_{cs}(4459)$) as the $\bar{D}Ξ_c$ ($\bar{D}^*Ξ_c$) molecular state with the spin-parity $J^P={\frac{1}{2}}^-$ (${\frac{3}…
In this work, we systemically investigate the molecular states from the $Σ^{(*)}_c\bar{D}^{(*)}-Λ_c\bar{D}^{(*)}$ interaction with the help of the Lagrangians with heavy quark and chiral symmetries in a quasipotential Bethe-Salpeter equation (qBSE) approach. The molecular states are produced from isodoublet (I=1/2) $Σ_c\bar{D}$ interaction with spin parity $J^P=1/2^-$ and $Σ_c\bar{D}^*$ interaction with $1/2^-$ and $ 3/2^-$. Their masses and widths are consistent with the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ observed at LHCb. The states, $Σ_c^*\bar{D}^*(1/2^-)$, $Σ_c^*\bar{D}^*(3/2^-)$ and…
Stimulated by the $P_{cs}(4459)$ reported by the LHCb Collaboration, we perform a single $Ξ_c\bar{D}^*$ channel and a coupled $Ξ_c\bar{D}^*/Ξ_c^*\bar{D}/Ξ_c^{\prime}\bar{D}^*/Ξ_c^*\bar{D}^*$ channel analysis by using a one-boson-exchange model. Our results indicate that the newly $P_{cs}(4459)$ cannot be a pure $Ξ_c\bar{D}^*$ molecular state, but a coupled $Ξ_c\bar{D}^*/Ξ_c^*\bar{D}/Ξ_c^{\prime}\bar{D}^*/Ξ_c^*\bar{D}^*$ bound state with $I(J^P)=0(3/2^-)$, where the $Ξ_c\bar{D}^*$ and $Ξ_c^*\bar{D}$ components are dominant. Meanwhile, we find the interactions from the $Ξ_c^{\prime}\bar{D}^*$ sy…
Recently, a new structure $Y(4626)$ was reported by the Belle Colloboration in the process $e^+e^-\to D_s^+D_{s1}(2536)^-$. In this work, we propose an assignment of the $Y(4626)$ as a ${D}^*_s\bar{D}_{s1}(2536)$ molecular state, which decays into the $D_s^+D_{s1}(2536)^-$ channel through a coupling between ${D}^*_s\bar{D}_{s1}(2536)$ and ${D}_s\bar{D}_{s1}(2536)$ channels. With the help of the heavy quark symmetry, the potential of the interaction ${D}^*_s\bar{D}_{s1}(2536)-{D}_s\bar{D}_{s1}(2536)$ is constructed within the one-boson-exchange model, and inserted into the quasipotential Bethe-…
In this article, we investigate the $\bar{D}Σ_c$, $\bar{D}Ξ^\prime_c$, $\bar{D}Σ_c^*$, $\bar{D}Ξ_c^*$, $\bar{D}^{*}Σ_c$, $\bar{D}^{*}Ξ^\prime_c$, $\bar{D}^{*}Σ_c^*$ and $\bar{D}^{*}Ξ_c^*$ pentaquark molecular states with strangeness and without strangeness via the QCD sum rules at length, pay much attention to the light flavor $SU(3)$ breaking effects, and make predictions for new pentaquark molecular states besides assigning the $P_c(4312)$, $P_c(4380)$, $P_c(4440)$, $P_c(4457)$ and $P_{cs}(4459)$ self-consistently. We can search for those pentaquark molecular states in the decays of the $Λ_b…
We discuss the possibility that the X(3872) can be a $D\bar{D}^*$ molecular bound state in the Bethe-Salpeter equation approach in the ladder and instantaneous approximations. We show that the $D\bar{D}^*$ bound state with quantum numbers $J^{PC}=1^{++}$ exists. We also calculate the decay width of $X(3872) \rightarrow γJ/ψ$ channel and compare our result with those from previous calculations.
In this work, we perform a systematical investigation about the possible hidden and doubly heavy molecular states with open and hidden strangeness from interactions of $D^{(*)}{\bar{D}}^{(*)}_{s}$/$B^{(*)}{\bar{B}}^{(*)}_{s}$, ${D}^{(*)}_{s}{\bar{D}}^{(*)}_{s}$/${B}^{(*)}_{s}{\bar{B}}^{(*)}_{s}$, ${D}^{(*)}D_{s}^{(*)}$/${B}^{(*)}B_{s}^{(*)}$, and $D_{s}^{(*)}D_{s}^{(*)}$/$B_{s}^{(*)}B_{s}^{(*)}$ in a quasipotential Bethe-Salpeter equation approach. The interactions of the systems considered are described within the one-boson-exchange model, which includes exchanges of light mesons and $J/ψ/Υ$ …
We investigate whether the newly observed narrow resonance $Z_{c}(4025)$ can be described as a $D^{*}\bar{D^{*}}$ molecular state with quantum numbers $J^{P}=1^{+}$. Using QCD sum rules, we consider contributions up to dimension six in the operator product expansion and work at leading order of $α_{s}$. The mass obtained for this state is $(4.05\pm 0.28) \mbox{GeV}$. It is concluded that $D^{*}\bar{D^{*}}$ molecular state is a possible candidate for $Z_{c}(4025)$.
In this talk we address two topics: The first one is an empirical explanation in terms of a new state $h_1$ of the peak in the $K^{*0}\bar{K}^{*0}$ invariant mass distribution close to threshold of this channel in the $J/ψ\to ηK^{*0}\bar{K}^{*0}$ decay. The second one is a theoretical description of the isospin $I=1$ $Z_c(3900)$ and $Z_c(4020)$ states in terms of molecular states of $D \bar D^*+ cc$ and $D^* \bar D^*$.
We study the $\bar{K} Ξ$ decay mode of the newly observed $Ω(2012)$ assuming that the $Ω(2012)$ is a dynamically generated state with spin-parity $J^P = 3/2^-$ from the coupled channel $S$-wave interactions of $\bar{K}Ξ(1530)$ and $ηΩ$. In addition we also calculate its $KπΞ$ three-body decay mode. It is shown that the so-obtained total decay width is in fair agreement with the experimental data. We compare our results with those of other recent studies and highlight differences among them.
In this work, we adopt the one-boson-exchange model to study the $D^{(*)}K^{(*)}$ interactions. With the same parameters, we can simultaneously reproduce the masses of the $D_{s0}(2317)$, $D_{s1}(2460)$, and $T_{c\bar{s}}^{a0(++)}(2900)$ recently observed by the LHCb collaboration in the hadronic molecular picture, where the $D_{s0}(2317)$, $D_{s1}(2460)$, and $T_{c\bar{s}}^{a0(++)}(2900)$ are regarded as the $DK[I(J^P)=0(0^+)]$, $D^*K[0(1^+)]$, and $D^*K^*[1(0^+)]$ charmed-strange molecular states, respectively. In addition, we extend to study the $Λ_cK^{(*)}$ and $Σ_cK^{(*)}$ interactions an…
In this work, we study the radiative and strong decay of $S$-wave $K\bar{K}_1(1400)$ molecular state within the effective Lagrangians approach and find the relation between the $K\bar{K}_1(1400)$ molecular state and the newly observed $η_1(1855)$ state by comparing with the BESIII observation. The prediction indicates that the decay width can reach up to $182.97^{+2.79}_{-3.50}$ MeV, which can be confronted with the experimental data. If the $η_1(1855)$ could be $S$-wave $K\bar{K}_1(1400)$ molecular state, the $K\bar{K}^{*}π$ three-body decay provides the dominant contribution, not the $ηη^{'}…
Recently, the LHCb Collaboration reported a new structure $P_{cs}(4459)$ with a mass of 19 MeV below the $Ξ_c \bar{D}^{*} $ threshold. It may be a candidate of molecular state from the $Ξ_c \bar{D}^{*} $ interaction. In the current work, we perform a coupled-channel study of the $Ξ_c^*\bar{D}^*$, $Ξ'_c\bar{D}^*$, $Ξ^*_c\bar{D}$, $Ξ_c\bar{D}^*$, $Ξ'_c\bar{D}$, and $Ξ_c\bar{D}$ interactions in the quasipotential Bethe-Salpeter equation approach. With the help of the heavy quark chiral effective Lagrangian, the potential is constructed by light meson exchanges. Two $Ξ_c \bar{D}^{*} $ molecular st…
In a one-boson-exchange model, we study molecular states of double-charm baryon ($Ξ_{cc}(3621)$) and a charmed meson ($D$ and $D^*$). Our model indicates that there exist two possible triple-charm molecular pentaquarks, a $Ξ_{cc}D$ state with $I(J^P)=0(1/2^-)$ and a $Ξ_{cc}D^*$ state with $I(J^P)=0(3/2^-)$. In addition, we also extend our formula to explore $Ξ_{cc}\bar{B}^{(*)}$, $Ξ_{cc}\bar{D}^{(*)}$, and $Ξ_{cc}B^{(*)}$ systems, and find more possible heavy flavor molecular pentaquarks, a $Ξ_{cc}\bar{B}$ state with $I(J^P)=0(1/2^-)$, a $Ξ_{cc}\bar{B}^*$ state with $I(J^P)=0(3/2^-)$, and $Ξ_{…
We study charmonium ($c\bar c n\bar n$), bottomonium ($b\bar b n\bar n$) and exotic ($cc\bar n\bar n$ and $bb\bar n\bar n$) four-quark states by means of a standard non-relativistic quark potential model. We look for possible bound states. Among them we are able to distinguish between meson-meson molecules and compact four-quark states.
In the paper, we construct eight color singlet-singlet type five-quark currents with distinguished isospins to study the $\bar{D}Ξ^{\prime}$, $\bar{D}Ξ_c^{*}$, $\bar{D}^{*}Ξ_c^{\prime}$ and $\bar{D}^{*}Ξ_c^{*}$ molecular states with strangeness via the QCD sum rules. Numerical results show that the central values of the pentaquark masses with higher (lower) isospin are slightly above (below) the thresholds of the corresponding meson-baryon pairs, and support assigning the $P_{cs}(4459)$ as the $\bar{D}Ξ_c^{*}$ molecular state with the quantum numbers $IJ^P=0{\frac{3}{2}}^-$. The other predicti…
QCD sum-rules are employed to determine whether the X(3872) can be described as a mixed state that couples to $J^{PC}=1^{++}$ charmonium hybrid and $\bar D D^*$ molecular currents. After calculating the mixed correlator of hybrid and molecular currents, we formulate the sum-rule in terms of a mixing parameter that interpolates between the pure molecular and hybrid scenarios. As the mixing parameter is increased from the pure molecular case, the predicted mass increases until it reaches a maximum value in good agreement with the X(3872) and the resulting sum-rule analysis appears more robust th…
We evaluate the partial decay widths for the semileptonic $Λ_b \to \bar ν_l l Λ_c(2595)$ and $Λ_b \to \bar ν_l l Λ_c(2625)$ decays from the perspective that these two $Λ^*_c$ resonances are dynamically generated from the $DN$ and $D^*N$ interaction with coupled channels. We find that the ratio of the rates obtained for these two reactions is compatible with present experimental data and is very sensitive to the $D^* N$ coupling, which becomes essential to obtain agreement with experiment. Together with the results obtained for the $Λ_b \to π^- Λ^*_c$ reactions, it gives strong support to the m…
We study the $B^+ \to J/ψωK^+ $ reaction, measured by the LHCb collaboration, and show that it is driven by the presence of two resonances, the $X(3940)$ and $X(3930)$, that are of molecular nature and couple most strongly to $D^* \bar{D}^*$, but also to $J/ψω$. Because of that, in the $J/ψω$ mass distribution we find a peak related to the excitation of the resonances and a cusp with large strength at the $D^* \bar{D}^*$ threshold.
Stimulated by the meson-baryon molecular interpretations of the $P_c$ states ($P_c(4312)/P_c(4440)/P_c(4457)$), we systematically study the interactions between an $S-$wave charm-strange baryon $Ξ_c^{(\prime,*)}$ and an anti-charmed meson $\bar{D}^{(*)}$ in a coupled channel analysis. Effective potentials for the $Ξ_c^{(\prime,*)}\bar{D}^{(*)}$ interactions in a one-boson-exchange model can be related to those in the $Σ_c^{(*)}\bar{D}^{(*)}$ systems by using the $SU(3)$ flavor symmetry and heavy quark symmetry. Our results can predict several promising hidden-charm molecular pentaquarks with s…
We study the $Z_{cs}(3985)$ state recently observed by the BESIII Collaboration in the one-boson-exchange model, assuming that it is a $\bar{D}_s^{(*)}D^{(*)}$ molecule, which has the quark content $c\bar{c}s\bar{q}$ with $q = u$, $d$. It is shown that the one-boson-exchange potential is too weak to generate dynamcally $\bar{D}_s D$, $\bar{D}^*_s D$, and $\bar{D}_sD^*$ states, while for the case of $\bar{D}^*_s D^*$, very loosely bound states are likely, with binding energies of the order of several MeV. We conclude that, the observed $Z_{cs}(3985)$ state, if confirmed by further experiments, …
In this article, we assign the $Y(4390)$ and $Y(4220)$ to be the vector molecular states $D\bar{D}_1(2420)$ and $D^*\bar{D}_0^*(2400)$, respectively, and study their masses and pole residues with the QCD sum rules in details. The present calculations only favor assigning the $Y(4390)$ to be the $D\bar{D}_1(1^{--})$ molecular state.
Considering the coupling of color $1 \otimes 1$ and $8 \otimes 8$ structures, we calculate the energy of the newly observed $X$(3915) as $S-$wave $D^*\bar{D^*}$ state in the Bhaduri, Cohler, and Nogami quark model by the Gaussian Expansion Method. Due to the color coupling, the bound state of $D^*\bar{D^*}$ with $J^{PC}=0^{++}$ is found, which is well consonant with the experimental data of the $X$(3915). The bound state of $B^*\bar{B^*}$ with $J^{PC}=0^{++}$ and $2^{++}$ are also predicted in this work.
In this article, we calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and study the $J^{PC}=0^{++}$, $1^{+-}$, $2^{++}$ $D^*\bar{D}^*$, $D_s^*\bar{D}_s^*$, $B^*\bar{B}^*$, $B_s^*\bar{B}_s^*$ molecular states with the QCD sum rules. In calculations, we use the formula $μ=\sqrt{M^2_{X/Y/Z}-(2{\mathbb{M}}_Q)^2}$ to determine the energy scales of the QCD spectral densities. The numerical results favor assigning the $Z_c(4020)$ and $Z_c(4025)$ as the $J^{PC}=0^{++}$, $1^{+-}$ or $2^{++}$ $D^*\bar{D}^*$ molecular states, the $Y(4140)$ as the …
Testing the molecular nature of the $Ω(2012)$ with the $ψ(3770) \to \barΩ \bar{K} Ξ$ and $ψ(3770) \to \barΩ \bar{K} Ξ^*(1530) (\bar Ω\bar K πΞ)$ reactions
We perform a theoretical analysis of the $Λ_b \to J/ψK^- p$ reaction from where a recent LHCb experiment extracts a $Λ(1405)$ contribution in the $K^- p$ spectrum close to threshold and two baryon states of hidden charm in the $J/ψ\,p$ spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and $J^P$ of the experiment, concretely some states built up from the $J/ψ\, N$, $\bar D^* Λ_c$, $\bar D^* Σ_c$, $\bar D Σ^*_c$ and $\bar D^* Σ^*_c$ coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are ab…
The interpretation of Y(4140) as a $D^{*}_s\bar{D}^{*}_s$ molecule is studied dynamically in the one boson exchange approach, where $σ$, $η$ and $ϕ$ exchange are included. Ten allowed $D^{*}_s\bar{D}^{*}_s$ states with low spin parity are considered, we find that the $J^{PC}=0^{++}$, $1^{+-}$, $0^{-+}$, $2^{++}$ and $1^{--}$ $D^{*}_s\bar{D}^{*}_s$ configurations are most tightly bound. We suggest the most favorable quantum numbers are $J^{PC}=0^{++}$ for Y(4140) as a $D^{*}_s\bar{D}^{*}_s$ molecule, however, $J^{PC}=0^{-+}$ and $2^{++}$ can not be excluded. We propose to search for the $1^{+-}…
We evaluate theoretically the interaction of the open bottom and strange systems $\bar B\bar K$, $\bar B^* \bar K$, $\bar B\bar K^*$ and $\bar B^*\bar K^*$ to look for possible bound states which could correspond to exotic non--quark-antiquark mesons since they would contain at least one $b$ and one $s$ quarks. The s-wave scattering matrix is evaluated implementing unitarity by means of the Bethe-Salpeter equation, with the potential kernels obtained from contact and vector meson exchange mechanisms. The vertices needed are supplied from Lagrangians derived from suitable extensions of the hidd…
We studied the $D\bar{D}^\ast/\bar{D}D^\ast$, $D^\ast\bar{D}^\ast$, $\bar{D}_s D^\ast/\bar{D}_s^\ast D$, $B\bar{B}^\ast/\bar{B}B^\ast$ and $B^\ast\bar{B}^\ast$ di-hadron interactions in chiral effective field theory ($χ$EFT) up to the next-to-leading (NLO) order. The above-threshold tetraquark states $Z_c(3900)$, $Z_c(4020)$, $Z_{cs}(3985)$, $Z_b(10610)$, $Z_b(10650)$ can be explained as the corresponding di-hadron resonances, respectively. We also studied the $Σ_c^{(\ast)}\bar{D}^{(\ast)}$ interactions to investigate the three hidden-charm pentaquarks $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$.…
Within the framework of the local hidden gauge approach, we have studied the near-threshold interaction of the $D^* \bar{D}^*$ channel with quantum numbers $I(J^{PC}) = 0(0^{++})$, $0(2^{++})$, $1(0^{++})$, and $1(2^{++})$, respectively. The contact interaction is taken into account alone, since it is expected to give the dominant contribution near the threshold. One pole, which is found in the case of the quantum numbers $I(J^{PC}) = 0(0^{++})$, could be associated to the $X(4014)$ recently observed by the Belle Collaboration. Thus, we suggest that the $X(4014)$ may be an $D^* \bar{D}^*$ mole…
In this work, the $Ω_c$-like molecular states are systematically investigated in a quasipotential Bethe-Salpeter equation approach. The relevant interactions $Ξ_c^{(*,')}\bar{K}^{(*)}$, $Ξ^{(*)}D^{(*)}$, and $Ω^{(*)}_c(π/η/ρ/ω)$ are described by light meson exchanges with the help of the effective Lagrangians with SU(3), chiral, and heavy quark symmetries. The obtained potential kernels of considered interactions are inserted into the quasipotential Bethe-Salpeter equation, and coupled-channel calculations are performed to find possible molecular states and its couplings to the channels consid…
In this work, we construct the color-singlet-color-singlet type six-quark pseudoscalar current to investigate the $\overlineΞ_{cc}Ξ_{cc}$ hexaquark molecular state with the QCD sum rules, the predicted mass $M_X \sim 7.2\,\rm{GeV}$ supports assigning the $X(7200)$ to be the $\overlineΞ_{cc}Ξ_{cc}$ hexaquark molecular state with the quantum numbers $J^{PC}=0^{-+}$. The $X(7200)$ can decay through fusions of the $\bar{c}c$ and $\bar{q}q$ pairs, we can search for the $X(7200)$ and explore its properties in the $J/ψJ/ψ$, $χ_{c1}χ_{c1}$, $D^*\bar{D}^*$ and $D_1\bar{D}_1$ invariant mass spectrum in …
Recently observed spectrum of $P_c$ states exhibits a strong link to $Σ_c \bar{D}^{(*)}$ thresholds. In spite of successful molecular interpretations, we still push forward to wonder whether there exist finer structures. Utilizing the effecitve lagrangians respecting heavy quark symmetry and chiral symmetry, as well as instantaneous Bethe-Salpeter equations, we investigate the $Σ_c \bar{D}^{(*)}$ interactions and three $P_c$ states. We confirm that $P_c(4312)$ and $P_c(4440)$ are good candidates of $Σ_c \bar{D}$ and $Σ_c \bar{D}^{*}$ molecules with spin-$\frac12$, respectively. Unlike other mo…
We study the structure of heavy quark spin (HQS) multiplets for heavy meson-baryon molecular states in a coupled system of $\bar{P}^{(*)}Σ_{Q}^{(*)}$, with constructing the one-pion exchange potential with S-wave orbital angular momentum. Using the light cloud spin basis, we find that there are four types of HQS multiplets classified by the structure of heavy quark spin and light cloud spin. The multiplets which have attractive potential are determined by the sign of the coupling constant for the heavy meson-pion interactions. Furthermore, the difference in the structure of light cloud spin gi…
We present a mechanism for $Ω_c \to π^+ Ω(2012)$ production through an external emission Cabibbo favored weak decay mode, where the $Ω(2012)$ is dynamically generated from the interaction of $\bar{K}Ξ^*(1530)$, $ηΩ$, with $\bar{K}Ξ$ as the main decay channel. The $Ω(2012)$ decays later to $\bar{K}Ξ$ in this picture, with results compatible with Belle data. The picture has as a consequence that one can evaluate the direct decay $Ω_c^0 \to π^+K^- Ξ^0$ and the decay $Ω_c^0 \to π^+\bar{K} Ξ^*$, $π^+ηΩ$ with direct coupling of $\bar{K}Ξ^*$ and $ηΩ$ to $K^- Ξ^0$. We show that, within uncertainties a…
In this work, we study the $D\bar{D}$, $DD$, $D\bar{D}_s$, $DD_s$, $D_s\bar{D}_s$ and $D_sD_s$ tetraquark molecular states with the $J^{PC}=0^{++}$ via the QCD sum rules. The prediction $M_{D_s\bar {D}_s} = 3.98\pm0.10\, \rm{GeV}$ is in very good agreement with the experimental value $M_{X(3960)} = 3956 \pm 5\pm 10 \,\rm{MeV}$ from the LHCb collaboration and supports assigning the $X(3960)$ as the $D_s^+D_s^-$ molecular state with the $J^{PC}=0^{++}$. We take account of our previous works on the four-quark states consisting of two color-neutral clusters, and acquire the mass spectrum of the gr…
We investigated the bound state problem of the S wave charged $D_1 \bar{D}^*$ ($D_1' \bar{D}^*$) system in a chiral quark model by solving the resonating group method equation. Our preliminary study does not favor the molecular assumption of $Z^+(4430)$. On the contrary, if $Z^+(4430)$ is really a molecule, its partner with opposite $G$-parity should also exist and probably may be found in the $π^+η_c(2S)$, $J/ψπ^+π^0$, or $ψ'π^+π^0$ channel. For the bottom systems, we found the existence of both $I^G$=$1^+$ and $I^G$=$1^-$ $B_1 \bar{B}^*$ ($B_1' \bar{B}^*$) molecules is possible.
The possible neutral $D^{(*)}\bar{D}^{(*)}$ and $B^{(*)}\bar{B}^{(*)}$ molecular states are studied in the framework of the constituent quark models, which is extended by including the $s$-channel one gluon exchange. Using different types of quark-quark potentials, we solve the four-body Schrödinger equation by means of the Gaussian expansion method. The bound states of $D^{(*)}\bar{D}^{(*)}$ with $J^{PC}=1^{++},2^{++}$ and $B^{(*)}\bar{B}^{(*)}$ with $J^{PC}=0^{++},1^{+-},1^{++},2^{++}$ are obtained. The molecular states $D^{*}\bar{D}$ with $J^{PC}=1^{++}$ and $B^{*}\bar{B}$ with $J^{PC}=1^{+…
We have calculated the mass spectra for the $\bar{D}_s^{(*)}D^{(*)}$ molecular states and $sc\bar q\bar c$ tetraquark states with $J^P=0^+, 1^+, 2^+$. The masses of the axial-vector $\bar{D}_sD^{*}$, $\bar{D}_s^{*}D$ molecular states and $\mathbf{1}_{[sc]} \oplus \mathbf{0}_{[\bar q \bar{c}]}$, $\mathbf{0}_{[sc]} \oplus \mathbf{1}_{[\bar q \bar{c}]}$ tetraquark states are predicted to be around 3.98 GeV, which are in good agreement with the mass of $Z_{cs}(3985)^-$ from BESIII \cite{besiii2020Zcs}. In both the molecular and diquark-antidiquark pictures, our results suggest that there may exist…
