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Hong-Wei Ke

Publications and source records attributed to Hong-Wei Ke.

At least 19 recordsLinked to original sources
arXiv2024

Weak decays of the triply heavy baryons in the three-quark picture with the light-front quark model

We investigate the weak decays of the triply heavy baryon $Ω_{QQQ}$ in the light-front quark model. Since $Ω_{QQQ}$ consists of three indistinguishable identical heavy quarks, the commonly adopted quark-diquark picture does not seem to be valid anymore. Instead, we employ the three-quark picture for baryons where the three quarks are regarded as individual quarks. We calculate the hadronic form factors for the transitions and give predictions for the decay widths of the semi-leptonic decay modes $Ω_{ccc}\to Ξ_{cc}/ Ω_{cc}+ l\barν_l$, $Ω_{bbb}\to Ξ_{bb}+ l \barν_l$ and the non-leptonic decay modes $Ω_{ccc}\to Ξ_{cc}/Ω_{cc}+ M$, $Ω_{bbb}\to Ξ_{bb}+ M$. Our study can be a guide for future experiments to discover the triply heavy baryons.

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arXiv2024

Study on the mixing of $Ξ_c$ and $Ξ'_c$ by the transition $Ξ_{b}\toΞ^{(')}_c$

Recently, the LHCb collaboration has observed the decays $Ξ^0_{b}\toΞ^+_{c}D^-_s$ and $Ξ^-_{b}\toΞ^0_{c}D^-_s$. They measured the relative branching fractions times the ratio of beauty-baryon production cross-sections $\mathcal{R}(\frac{Ξ^0_b}{Λ_b})\equiv\frac{σ(Ξ_b^0)}{σ(Λ^0_b)}\times\frac{B(Ξ^0_{b}\toΞ^+_{c}D^-_s)}{B(Λ^0_{b}\toΛ^+_{c}D^-_s)}$ and $\mathcal{R}(\frac{Ξ^-_b}{Λ_b})\equiv\frac{σ(Ξ^-_b)}{σ(Λ^0_b)}\times\frac{B(Ξ^-_{b}\toΞ^0_{c}D^-_s)}{B(Λ^0_{b}\toΛ^+_{c}D^-_s)}$. Once the ratio $\frac{σ(Ξ_b^0)}{σ(Λ^0_b)}$ or $\frac{σ(Ξ_b^-)}{σ(Λ^0_b)}$ is known, one can determine the relative branching fractions which can be used to exam the mixing of $Ξ_c$ and $Ξ'_c$. In previous literature, $Ξ_c$ and $Ξ'_c$ were assumed to belong to SU(3)$_F$ antitriple and sextet, respectively. However, recent experimental measurements such as the ratio $Γ(Ξ_{cc}\toΞ_cπ^+)/Γ(Ξ_{cc}\toΞ'_cπ^+)$ indicate the spin-flavor structures of $Ξ_{c}$ and $Ξ'_{c}$ are a mixture of $Ξ^{\bar 3}_{c}$ and $Ξ^{6}_{c}$. The exact value of mixing angle $θ$ is still under debate. In theoretical models, the mixing angle was fitted to be about $16.27^\circ\pm2.30^\circ$ or $85.54^\circ\pm2.30^\circ$ based on decay channels $Ξ_{cc} \toΞ^{(')}_{cc} $. While in lattice calculation, a small angle ($1.2^\circ\pm0.1^\circ$) is preferred. To address such discrepancy and test the mixing of $Ξ_c$ and $Ξ'_c$, here we propose the analysis of semileptonic and non-leptonic decays of $Ξ_{b}\toΞ_{c}$ and $Ξ_{b}\toΞ^{'}_{c}$. We calculate the decay rate of $Ξ_{b}\toΞ_{c}$ and $Ξ_{b}\toΞ^{'}_{c}$ based on light-front quark model and study the effect of the mixing angle on the ratios of weak decays $Ξ_{b}\toΞ_{c}$ and $Ξ_{b}\toΞ^{'}_{c}$.....

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arXiv2023

Study on the possible molecular states composed of $Λ_c\bar D^*$, $Σ_c\bar D^*$, $Ξ_c\bar D^*$ and $Ξ_c'\bar D^*$ in the Bethe-Salpeter frame based on the pentaquark states $P_c(4440)$, $P_c(4457)$ and $P_{cs}(4459)$

The measurements on a few pentaquarks states $P_c(4440)$, $P_c(4457)$ and $P_{cs}(4459)$ excite our new interests about their structures. Since the masses of $P_c(4440)$ and $P_c(4457)$ are close to the threshold of $Σ_c\bar D^*$, in the earlier works, they were regarded as molecular states of $Σ_c\bar D^*$ with quantum numbers $I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$ and $\frac{1}{2}(\frac{3}{2}^-)$, respectively. In a similar way $P_{cs}(4459)$ is naturally considered as a $Ξ_c\bar D^*$ bound state with $I=0$. Within the Bethe-Salpeter (B-S) framework we systematically study the possible bound states of $Λ_c\bar D^*$, $Σ_c\bar D^*$, $Ξ_c\bar D^*$ and $Ξ_c'\bar D^*$. Our results indicate that $Σ_c\bar D^*$ can form a bound state with $I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$, which corresponds to $P_c(4440)$. However for the $I(J^P)=\frac{1}{2}(\frac{3}{2}^-)$ system the attraction between $Σ_c$ and $\bar D^*$ is too weak to constitute a molecule, so $P_{c}(4457)$ may not be a bound state of $Σ_c\bar D^*$ with $I(J^P)=\frac{1}{2}(\frac{3}{2}^-)$. As $Ξ_c\bar D^*$ and $Ξ_c'\bar D^*$ systems we take into account of the mixing between $Ξ_c$ and $Ξ'_c$ and the eigenstets should include two normal bound states $Ξ_c\bar D^*$ and $Ξ_c'\bar D^*$ with $I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$ and a loosely bound state $Ξ_c\bar D^*$ with $I(J^P)=\frac{1}{2}(\frac{3}{2}^-)$. The conclusion that two $Ξ_c\bar D^*$ bound states exist, supports the suggestion that the observed peak of $P_{cs}(4459)$ may hide two states $P_{cs}(4455)$ and $P_{cs}(4468)$. Based on the computations we predict a bound state $Ξ_c'\bar D^*$ with $I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$ but not that with $I(J^P)=\frac{1}{2}(\frac{3}{2}^-)$. Further more accurate experiments will test our approach and results.

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arXiv2023

Study on the weak decay between two heavy baryons $ \mathcal{B}_i(\frac{1}{2}^+)\to \mathcal{B}_f(\frac{3}{2}^+)$ in the light-front quark model

In this work, we study the weak decay between two heavy baryons $ \mathcal{B}_i(\frac{1}{2}^+)\to \mathcal{B}_f(\frac{3}{2}^+)$ in the light-front quark model where three-quark picture is employed for baryon. We derive general form of transition amplitude of $ \mathcal{B}_i(\frac{1}{2}^+)\to \mathcal{B}_f(\frac{3}{2}^+)$, and analyze two specific cases of transitions: the weak decays of single heavy baryon $Σ_{b} \to Σ_{c}^*$ and the decays of double-charmed baryon $Ξ_{cc}\to Σ_{c}^*(Ξ_{c}^*)$. We compute the hadronic form factors for the transitions and apply them to study the decay widths of the semi-leptonic $\mathcal B_i(\frac{1}{2}^+)\to\mathcal B_f(\frac{3}{2}^+) l\barν_l$ and non-leptonic $\mathcal B_i(\frac{1}{2}^+)\to\mathcal B_f(\frac{3}{2}^+)M$. Previously we studied the transition $Σ_{b} \to Σ_{c}^*$ with the quark-diquark picture of baryon in the light-front quark model. Here we revisit this transition with three-quark picture of baryon. At the quark level, the transition $Σ_{b} \to Σ_{c}^*$ is induced by the $b\rightarrow c$ transition.The subsystem of the two unchanged light quarks which possesses definite and same spin in initial and final state can be viewed as a spectator, so the spectator approximation can be applied directly. For the weak decay of doubly charmed baryon $Ξ_{cc}$, a $c$ quark decays to a light quark $q_1$, so both the initial state $cc$ and final state $q_1q_2$ ($q_1$ and the original $q_2$ in initial state may be the same flavor quarks) which possess definite spin are no longer spectators. A rearrangement of quarks for initial and final states is adopted to isolate the unchanged subsystem $cq_2$ which can be viewed as the spectator approximately. Future measurements on these channels will constrain the nonperturbative parameter in the wavefunctions and test the model predictions.

hep-ph↗
arXiv2023

Searching for doubly charmed tetraquark candidates $T_{cc}$ and $T_{cc\bar{s}}$ in $B_c$ decays

In this work, we propose to search for the exotic doubly charmed meson $T_{cc}^+$ and its analog $T_{cc\bar{s}}^+$ in $B_c^+$ decays, which provide a good environment for the formation of the exotic state containing double charm quarks. Within the molecular scheme, the production of $T_{cc}^+$ and $T_{cc\bar{s}}^+$ through various rescattering processes with different intermediate states are investigated. For the moderate values of model parameters, the branching ratios of $B_c^+$ decaying into $T_{cc}^+ \bar{D}^{0}$, $T_{cc}^+ \bar{D}^{*0}$, $T_{cc\bar{s}}^+ \bar{D}^{0}$ and $T_{cc\bar{s}}^+ \bar{D}^{*0}$ are estimated to be of the order of $10^{-7}$, $10^{-5}$, $10^{-6}$ and $10^{-4}$, respectively, which may be tested by future experiments.

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arXiv2022

Possible molecular states of $\bar D^{*}K^{*}$ ($ D^{*}K^{*}$) and the new exotic states $X_0(2900)$ and $X_1(2900)$ ($T^a_{cs0}(2900)^0$ and $T^a_{cs0}(2900)^{++}$)

Two iso-singlet hadron states $X_0(2900)$ and $X_1(2900)$ with $J=0$ and 1 respectively, discovered by the LHCb collaboration in 2020, were identified as molecular bound states of $\bar D^*K^*$. Recently two structures $T^a_{cs0}(2900)^0$ and $T^a_{cs0}(2900)^{++}$ have been observed at the hadron spectra, one would suspect if they also are molecular states of $D^*$ and $K^*$. As long as they were of the molecular structures of $D^*K^*$, the hadron states must be in an iso-vector, namely $T^a_{cs0}(2900)^0$ and $T^a_{cs0}(2900)^{++}$ were $I_3=-1, 1$ components of the iso-vector. If it is the case, the corresponding $T^a_{cs0}(2900)^+$ of ($I=1,I_3=0$) and $T^{'a}_{cs0}(2900)^{+}$ of $I=0,I_3=0$ so far evade experimental observation, but should be found by the future experiments. To testify this ansatz, in this paper we study the possible molecular structures of $\bar D^{*}K^{*}$ and $D^{*}K^{*}$ within the Bethe-Salpeter (B-S) framework. With reasonable input parameters it is found that $\bar D^{*}K^{*}$ iso-scalar systems with $J^P=0^+$ and $1^+$ are solutions. The result supports the ansatz of $X_0(2900)$ ($X_1(2900)$) being molecular states of $\bar D^*K^{*}$. Whereas for the system of $ D^{*}K^{*}$ with $I=1$ the corresponding B-S equation has no solution. Thus we can draw a clear conclusion that $T^a_{cs0}(2900)^0$ and $T^a_{cs0}(2900)^{++}$ should not be bound states of $ D^{*}$ and $K^{*}$. The two structures observed by the LHCb collaboration may be caused by dynamics, such as the well-recognized triangle anomalies or other mechanisms.

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arXiv2022

Possibility of $T_{c\bar{s}}(2900)$ as the resonance-like structure induced by threshold effects

We investigate the process $B\to \bar{D}D_s π$ via several rescattering processes. It is shown that the triangle singularity (TS) peak around the $D^*K^*$ threshold generated from the $χ_{c1}K^* D^*$ loop is relatively narrow, which may simulate the resonance-like structure $T_{c\bar{s}}(2900)$ recently observed by LHCb in the $D_sπ$ spectrum. However, the TS peak around the $D_s^*ρ$ threshold generated from the $D^{**} D_s^* ρ$ loop is smoothed by the broad width of $ρ$, which itself can hardly describe the $T_{c\bar{s}}(2900)$ structure. A TS signal around the $DK$ threshold generated from the $χ_{c0}K D $ loop is also predicted.

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arXiv2022

Revisiting the transition $Ξ^{+}_{cc}\toΞ^{(')+}_c$ to understand the data from LHCb

The LHCb collaboration newly measured the decay rate of doubly charmed baryon $Ξ^{++}_{cc}\toΞ^{'+}π^+$ and a ratio of its branching fraction with respect to that of the decay $Ξ^{++}_{cc}\toΞ^{+}π^+$ is reported as $1.41\pm 0.17\pm 0.10$. This result conflicts with the theoretical predictions made by several groups. In our previous work, following the prescription given in early literature where the $us$ diquark in $Ξ^{+}_{c}$ is assumed to be a scalar whereas in $Ξ^{'+}_{c}$ is a vector i.e. the spin-flavor structure of $Ξ^{+}_{c}$ is $[us]_0 c$ and that of $Ξ^{'+}_{c}$ is $[us]_1 c$, we studied the case of $Ξ^{++}_{cc}\toΞ^{(')+}$ with the light front quark model. Numerically we obtained $Γ(Ξ^{++}_{cc}\toΞ^{'+}π^+)/Γ(Ξ^{++}_{cc}\toΞ^{+}π^+)=0.56\pm0.18$ which is about half of the data. While abandoning the presupposition, we suppose the spin-flavor structure of $us$ in $Ξ^{+}_{c}$ may be a mixture of scalar and vector, namely the spin-flavor function of $Ξ^{+}_{c}$ could be ${\rm cos}θ\, [us]_{0}[c]+{\rm sin}θ\, [us]_{1}[c]$. An alternative combination $-{\rm sin}θ\,[us]_{0}[c]+{\rm cos}θ\, [us]_{1}[c]$ would correspond to $Ξ^{'+}_{c}$. Introducing the mixing mechanism the ratio $Γ(Ξ^{++}_{cc}\toΞ^{'+}π^+)/Γ(Ξ^{++}_{cc}\toΞ^{+}π^+)$ depends on the mixing angle $θ$. With the mixing scenario, the theoretical prediction on the ratio between the transition rate of $Ξ^{+}_{cc}\toΞ^{'+}_c$ and that of $Ξ^{+}_{cc}\toΞ^{+}_c$ can coincide with the data as long as $θ=16.27^\circ\pm2.30^\circ$ or $85.54^\circ\pm2.30^\circ$ is set. Definitely, more precise measurements on other decay portals of $Ξ^{+}_{cc}$ are badly needed for testing the mixing mechanism and further determining the mixing angle.

hep-ph↗
arXiv2022

The study of possible molecular states of $D_s^{(*)}D_s^{(*)}$ and $B_s^{(*)}B_s^{(*)}$

Recently the LHCb collaboration reported a new exotic state $T^+_{cc}$ which is conjectured to be a molecular state of $D^0D^{*+}$ (or $D^{*0}D^{+}$) theoretically. Belle Collaboration also searched for tetraquark state $X_{ccss}$ in $D_sD_s (D^*_sD^*_s )$ final states but no significant signals were observed, which did not rule out the possibility of $X_{ccss}$ to be a molecular state of $D_sD_s (D^*_sD^*_s )$. Inspired by these experimental results on double charmed exotic state, in this paper we study whether the molecular bound states of $D_s^{(*)}D_s^{(*)}$ and $B_s^{(*)}B_s^{(*)}$ can exist with the Bethe-Salpeter (B-S) equation approach. We employ heavy meson chiral perturbation theory with one boson-exchange approximation to calculate the interaction kernels in the B-S equations. Our numerical results suggest that two $B_s^{*}$ mesons perhaps form a $0^+$ molecular state. Future experimental search for $X_{ccss}$ states in other decay channels may shed light on the structure of double charmed exotic state.

hep-ph↗
arXiv2022

Possible Molecular States of $D^{(*)}D^{(*)}$ and $B^{(*)}B^{(*)}$ within the Bethe-Salpeter framework

Recently the LHCb collaboration reported a new exotic state $T^+_{cc}$ which possesses $cc\bar u\bar d$ flavor structure. Since its mass is very close to the threshold of $D^0D^{*+}$ (or $D^{*0}D^{+}$) and its width is very narrow, it is inclined to conjecture that $T^+_{cc}$ is a molecular state of $D^0D^{*+}$ (or $D^{*0}D^{+}$). In this paper we study the possible molecular structures of $D^{(*)}D^{(*)}$ and $B^{(*)}B^{(*)}$ within the Bethe-Salpeter (B-S) framework. We employ one boson exchange model to stand the interaction kernels in the B-S equations. With reasonable input parameters we find the isospin eigenstate $\frac{1}{\sqrt{2}}(D^0D^{*+}-D^{*0}D^{+})$ ($J^P=1^+$) constitutes a solution, which supports the ansatz of $T^+_{cc}$ being a molecular state of $D^0D^{*+}$ (or $D^{*0}D^{+}$). With the same parameters we also find that the isospin-1 state $\frac{1}{\sqrt{2}}(D^{*0}D^{*+}+D^{*0}D^{*+})$ ($J^P=0^+$) can exist. Moreover, we also study the systems of $B^{(*)}B^{(*)}$ and their counterparts exist as possible molecular states. Consistency of theoretical computations based on such states with the data of the future experiments may consolidate the molecular structure of the exotic state $T^+_{cc}$.

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arXiv2021

The weak decays of $Ξ^{(')}_{c}\toΞ$ in the light-front quark model

Without contamination from the final state interactions, the calculation of the branching ratios of semileptonic decays $Ξ^{(')}_{c}\toΞ+e^+ν_e$ may provide us more information about the inner structure of charmed baryons. Moreover, by studying those processes, one can better determine the form factors of $Ξ_c\toΞ$ which can be further applied to relevant estimates. In this work, we use the light-front quark model to carry out the computations where the three-body vertex functions for $Ξ_c$ and $Ξ$ are employed. To fit the new data of the Belle II, we re-adjust the model parameters and obtain $β_{s[sq]}=1.07$ GeV which is 2.9 times larger than $β_{s\bar s}=0.366$ GeV. This value may imply that the $ss$ pair in $Ξ$ constitutes a more compact subsystem. Furthermore, we also investigate the non-leptonic decays of $Ξ^{(')}_c\to Ξ$ which will be experimentally measured soon, so our model would be tested by consistency with the new data.

hep-ph↗
arXiv2021

Tetraquark state $X(6900)$ and the interaction between diquark and antidiquark

Recently LHCb declared a new structure $X(6900)$ in the final state di-$J/ψ$ which is popularly regarded as a $cc$-$\bar c\bar c$ tetraquark state. %popularly. Within the Bethe-Salpeter (B-S) frame we study the possible $cc$-$\bar c\bar c$ bound states and the interaction between diquark ($cc$) and antidiquark ($\bar c\bar c$). In this work $cc$ ($\bar c\bar c$) is treated as a color anti-triplet (triplet) axial-vector so the quantum numbers of $cc$-$\bar c\bar c$ bound state are $0^+$, $1^+$ and $2^+$. Learning from the interaction in meson case and using the effective coupling we suggest the interaction kernel for diquark and antidiquark system. Then we deduce the B-S equations for different quantum numbers. Solving these equations numerically we find the spectra of some excited states can be close to the mass of $X(6900)$ when we assign appropriate values for parameter $κ$ introduced in the interaction (kernel).We also briefly calculate the spectra of $bb$-$\bar b\bar b$ bound states. Future measurement of $bb$-$\bar b\bar b$ state will help us to determine the exact form of effective interaction.

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arXiv2021

Threshold effects as the origin of $Z_{cs}(4000)$, $Z_{cs}(4220)$ and $X(4700)$ observed in $B^+\to J/ψϕK^+$

We investigate the $B^+\to J/ψϕK^+$ decay via various rescattering diagrams. Without introducing genuine exotic resonances, it is shown that the $Z_{cs}(4000)$, $Z_{cs}(4220)$ and $X(4700)$ reported by the LHCb collaboration can be simulated by the $J/ψK^{*+}$, $ψ^\prime K^+$ and $ψ^\prime ϕ$ threshold cusps, respectively. These cusps are enhanced by some nearby triangle singularities. The $X(4685)$ with $J^P=1^+$ cannot be well simulated by the threshold effects in our model, which implies that it may be a genuine resonance.

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arXiv2020

Revisiting the determining fraction of glueball component in $f_0$ mesons via radiative decays of $J/ψ$

QCD theory predicts the existence of glueballs, but so far all experimental endeavors have failed to identify any such states. To remedy this discrepancy between QCD, which has proven to be a successful theory for strong interactions, and the failure of experimental searches for glueballs, one is tempted to accept the promising interpretation that the glueballs mix with regular $q\bar q$ states of the same quantum numbers. The lattice estimate of the masses of pure $0^{++}$ glueballs ranges from 1 to 2 GeV, which is the region of the $f_0$ family. Thus many authors suggest that the $f_0$ mesonic series is an ideal place to study possible mixtures of glueballs and $q\bar q$. In this paper, following the strategy proposed by Close, Farrar and Li, we try to determine the fraction of glueball components in $f_0$ mesons using the measured mass spectra and the branching ratios of $J/ψ$ radiative decays into $f_0$ mesons. Since the pioneering papers by Close et al., more than 20 years has elapsed and more accurate measurements have been done by several experimental collaborations, so it is time to revisit this interesting topic using new data. We suppose $f_0(500)$ and $f_0(980)$ to be pure quark states, while for $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$, to fit both the experimental data of $J/ψ$ radiative decay and their mass spectra, glueball components are needed. Moreover, the mass of the pure $0^{++}$ glueball is phenomenologically determined.

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arXiv2020

A natural interpretation on the data of $Λ_c\toΣπ$

Even though the Standard Model (SM) has achieved great success, its application to the field of low energies still lacks solid foundation due to our limited knowledge on non-perturbative QCD. Practically, all theoretical calculations of the hadronic transition matrix elements are based various phenomenological models. There indeed exist some anomalies in the field which are waiting for interpretations. The goal of this work is trying to solve one of the anomalies: the discrepancy between the theoretical prediction on the sign of the up-down asymmetry parameter of $Λ_c\toΣπ$ and the experimental measurement. In the literatures several authors calculated the rate and determined the asymmetry parameter within various schemes, but there exist obvious loopholes in those adopted scenarios. To solve the discrepancy between theory and data, we suggest that not only the direct transition process contributes to the observed $Λ_c\toΣπ$, but also other portals such as $Λ_c\to Λρ$ also play a substantial role via an isospin-conserving re-scattering $Λρ\toΣπ$. Taking into account of the effects induced by the final state interaction, we re-evaluate the relevant quantities. Our numerical results indicate that the new theoretical prediction based on this scenario involving an interference between the direct transition of $Λ_c\toΣπ$ and the portal $Λ_c\toΛρ\toΣπ$ can make both the decay rate and sign of the asymmetry parameter to be consistent with data.

hep-ph↗
arXiv2020

Triangle singularity as the origin of $X_0(2900)$ and $X_1(2900)$ observed in $B^+\to D^+ D^- K^+$

The LHCb collaboration reported the observation of a narrow peak in the $D^- K^+$ invariant mass distributions from the $B^+\to D^+ D^- K^+$ decay. The peak is parameterized in terms of two resonances $X_0(2900)$ and $X_1(2900)$ with the quark contents $\bar{c}\bar{s}ud$, and their spin-parity quantum numbers are $0^+$ and $1^-$, respectively. We investigate the rescattering processes which may contribute to the $B^+\to D^+ D^- K^+$ decays. It is shown that the $D^{*-}K^{*+}$ rescattering via the $χ_{c1}K^{*+}D^{*-}$ loop or the $\bar{D}_{1}^{0}K^{0}$ rescattering via the $D_{sJ}^{+}\bar{D}_{1}^{0}K^{0}$ loop simulate the $X_0(2900)$ and $X_1(2900)$ structures. Such phenomena are due to the analytical property of the scattering amplitudes with the triangle singularities located to the vicinity of the physical boundary.

hep-ph↗
arXiv2020

Study on the possible molecular state composed of $D^*_s\bar D_{s1} $ within the Bethe-Salpeter framework

Recently a vector charmonium-like state $Y(4626)$ was observed in the portal of $D^+_sD_{s1}(2536)^-$. It intrigues an active discussion on the structure of the resonance because it has obvious significance for gaining a better understanding on its hadronic structure with suitable inner constituents. It indeed concerns the general theoretical framework about possible structures of exotic states. Since the mass of $Y(4626)$ is slightly above the production threshold of $D^+_s\bar D_{s1}(2536)^-$ whereas below that of $D^*_s\bar D_{s1}(2536)$ with the same quark contents as that of $D^+_s\bar D_{s1}(2536)^-$, it is natural to conjecture $Y(4626)$ to be a molecular state of $D^{*}_s\bar D_{s1}(2536)$, as suggested in literature. Confirming or negating this allegation would shed light on the goal we concern. We calculate the mass spectrum of a system composed of a vector meson and an axial vector i.e. $D^*_s\bar D_{s1}(2536)$ within the framework of the Bethe-Salpeter equations. Our numerical results show that the dimensionless parameter $λ$ in the form factor which is phenomenologically introduced to every vertex, is far beyond the reasonable range for inducing an even very small binding energy $ΔE$. It implies that the $D^*_s\bar D_{s1}(2536)$ system cannot exist in the nature as a hadronic molecule in this model, so that we may not think the resonance $Y(4626)$ to be a bound state of $D^*_s\bar D_{s1}(2536)$, but something else, for example a tetraquark and etc.

hep-ph↗
arXiv2020

Study on possible molecular states composed of $Λ_c\bar D$ ($Λ_b B$) and $Σ_c\bar D$ ($Σ_b B$) within the Bethe-Salpeter framework

$P_c(4312)$ observed by the LHCb collaboration is confirmed as a pentaquark and its structure, production, and decay behaviors attract great attention from theorists and experimentalists. Since its mass is very close to sum of $Σ_c$ and $\bar D$ masses, it is naturally tempted to be considered as a molecular state composed of $Σ_c$ and $\bar D$. Moreover, $P_c(4312)$ is observed in the channel with $J/ψp$ final state, requiring that isospin conservation $P_c(4312)$ is an isospin-1/2 eigenstate. In literature, several groups used various models to estimate its spectrum. We systematically study the pentaquarks within the framework of the Bethe-Salpeter equation; thus $P_c(4312)$ is an excellent target because of the available data. We calculate the spectrum of $P_c(4312)$ in terms of the Bethe-Salpter equations and further study its decay modes. Some predictions on other possible pentaquark states that can be tested in future experiments are made.

hep-ph↗