arXiv subjects

Ming-Zhu Liu

Publications and source records attributed to Ming-Zhu Liu.

At least 55 records · Page 3Linked to original sources

arXiv2021

$P_{c}(4457) \to P_{c}(4312) π/γ$ in the molecular picture

The three pentaquark states, $P_{c}(4312)$, $P_{c}(4440)$, and $P_{c}(4457)$, discovered by the LHCb Collaboration in 2019, can be nicely arranged into a multiplet of $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$ of seven molecules dictated by heavy quark spin symmetry. In this work we employ the effective Lagrangian approach to investigate the two decay modes of $P_{c}(4457)$, $P_{c}(4457) \to P_{c}(4312) π$ and $P_{c}(4457) \to P_{c}(4312) γ$, via the triangle mechanism, assuming that $P_{c}(4457)$ and $P_{c}(4312)$ are $\bar{D}^{\ast}Σ_{c}$ and $\bar{D}Σ_{c}$ bound states but the spin of $P_{c}(4457)$ can be either 1/2 or 3/2. Our results show that the spin of $P_{c}(4457)$ can not be discriminated through these two decay modes. The decay widths of $P_{c}(4457) \to P_{c}(4312) π$ and $P_{c}(4457) \to P_{c}(4312) γ$ are estimated to be of order of 100 keV and 1 keV, respectively. The ratio of the partial decay widths of $P_{c}(4457) \to P_{c}(4312) π$ to $P_{c}(4457) \to P_{c}(4312) γ$ is similar to the ratio of $D^{\ast}\to Dπ$ to $D^{\ast}\to Dγ$, which could be used to check the molecular nature of $P_{c}(4457)$ and $P_{c}(4312)$ if they can be observed in the future.

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arXiv2021

$D_{s0}(2590)$ as a dominant $c\bar{s}$ state with a small $D^*K$ component

The recently discovered $D_{s0}(2590)$ state by the LHCb collaboration was regarded as the first excited state of $^1S_{0}$ charmed-strange meson. Its mass is, however, lower than the Godfrey-Isgur quark model prediction by about 80 MeV. In this work, we take into account the $D^{\ast}K$ contribution to the bare $c\bar{s}$ state, and show that the coupled-channel interaction induces an 88 MeV shift with respect to the conventional quark model $c\bar{s}$ state, which is much closer to the experimental mass. Our study shows that in addition to $S$-wave, $P$-wave coupled-channel interactions also play a role for hadrons located close to two-hadron thresholds. We further scrutinize the unquenched quark model results with a model independent approach. It is shown that the two-body $D^*K$ decay width is proportional to the weight of the $D^*K$ component. To saturate the experimental total decay width with the $D^*K$ partial decay width we need a weight of about 60\% while to reproduce the unquenched quark model result a weight of about 5\% is needed. Therefore, we encourage future experimental studies on the two-body $D^*K$ partial decay of $D_{s0}(2590)$.

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arXiv2021

Discovery of the doubly charmed $T_{cc}^+$ state implies a triply charmed $H_{ccc}$ hexaquark state

The doubly charmed exotic state $T_{cc}$ recently discovered by the LHCb Collaboration could well be a $DD^{*}$ molecular state long predicted in various theoretical models, in particular, the $DD^*$ isoscalar axial vector molecular state predicted in the one-boson-exchange model. In this work, we study the $DDD^*$ system in the Gaussian Expansion Method with the $DD^*$ interaction derived from the one-boson-exchange model and constrained by the precise binding energy of $273\pm63$ keV of $T_{cc}$ with respect to the $D^{*+}D^0$ threshold. We show the existence of a $DDD^*$ state with a binding energy of a few hundred keV and spin-parity $1^-$. Its main decay modes are $DDDπ$ and $DDDγ$. The existence of such a state could in principle be confirmed with the upcoming LHC data and will unambiguously determine the nature of the $T_{cc}^+$ state and of the many exotic state of similar kind, thus deepening our understanding of the non-perturbative strong interaction.

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arXiv2021

Prediction of an $Ω_{bbb}Ω_{bbb}$ dibaryon in the extended one-boson exchange model

Ever since Yukawa proposed that the pion is responsible for mediating the nucleon-nucleon interaction, meson exchanges have been widely used in understanding hadron-hadron interactions. The most studied mesons are the $σ$, $π$, $ρ$, and $ω$, while other heavier mesons are often argued to be less relevant because they lead to short range interactions. However, the ranges of interactions should be compared with the size of the system under study but not in absolute terms. In this work, we propose that one charmoninium exchange is responsible for the formation of the $Ω_{ccc}Ω_{ccc}$ dibaryon, recently predicted by lattice QCD simulations. The same approach can be extended to the strangeness and bottom sectors, leading to the prediction on the existence of $ΩΩ$ and $Ω_{bbb}Ω_{bbb}$ dibaryons, while the former is consistent with existing lattice QCD results, the latter remains to checked. In addition, we show that the Coulomb interaction may break up the $Ω_{ccc}Ω_{ccc}$ pair but not the $Ω_{bbb}Ω_{bbb}$ and $ΩΩ$ dibaryons, particularly, the latter.

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arXiv2021

Hidden charm pentaquark with strangeness $P_{cs}^*(4739)$ as a $Σ_{c}\bar{D}\bar{K}$ bound state

Motivated by the recent discovery of the first hidden charm pentaquark state with strangeness $P_{cs}(4459)$ by the LHCb Collaboration, we study the likely existence of a three-body $Σ_{c}\bar{D}\bar{K}$ bound state, which shares the same minimal quark content as $P_{cs}(4459)$. The $Σ_{c}\bar{D}$ and $DK$ interactions are determined by reproducing $P_c(4312)$ and $D_{s0}^*(2317)$ as $Σ_c\bar{D}$ and $\bar{D}\bar{K}$ molecules, respectively, while the $Σ_c\bar{K}$ interaction is constrained by chiral effective theory. We indeed find a three-body bound state by solving the Schrödinger equation using the Gaussian Expansion Method, which can be viewed as an excited hidden charm pentaquark state with strangeness, $P_{cs}^*(4739)$, with $I(J^P)=1(1/2^+)$ and a binding energy of $77.8^{+25}_{-10.3}$ MeV. We further study its strong decays via triangle diagrams and show that its partial decay widths into $DΞ_c'$ and $D_s^*Σ_c$ are of a few ten's MeV, with the former being dominant.

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arXiv2021

One way to verify the molecular picture of exotic hadrons --from $DK$ to $DDK/D\bar{D}^{(*)}K$

Starting from 2003, a large number of the so-called exotic hadrons, such as $X(3872)$ and $D_{s0}^*(2317)$, were discovered experimentally. Since then, understanding the nature of these states has been a central issue both theoretically and experimentally. As many of these states are located close to two hadron thresholds, they are believed to be molecular states or at least contain large molecular components. We argue that if they are indeed molecular states, in the way that the deuteron is a bound state of proton and neutron, then molecular states of three or more hadrons are likely, in the sense that atomic nuclei are bound states of nucleons. Following this conjecture, we study the likely existence of $DDK$, $D\bar{D}K$, and $D\bar{D}^{*}K$ molecular states. We show that within the theoretical uncertainties of the two-body interactions deduced, they most likely exist. Furthermore, we predict their strong decays to help guide future experimental searches. In addition, we show that the same approach can indeed reproduce some of the known three-body systems from the two-body inputs, such as the deuteron-triton and the $Λ(1405)$-$\bar{K}NN$ systems.

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arXiv2021

Understanding $P_{cs}(4459)$ as a hadronic molecule in the $Ξ_b^-\to J/ψΛK^-$ decay

Recently, the LHCb Collaboration reported on the evidence for a hidden charm pentaquark state with strangeness, i.e., $P_{cs}(4459)$, in the $J/ψΛ$ invariant mass distribution of the $Ξ_b^-\to J/ψΛK^-$ decay. In this work, assuming that $P_{cs}(4459)$ is a $\bar{D}^*Ξ_c$ molecular state, we study this decay via triangle diagrams $Ξ_b\rightarrow \bar{D}_s^{(*)}Ξ_c\to (\bar{D}^{(*)}\bar{K})Ξ_c\to P_{cs} \bar{K}\to (J/ψΛ) \bar{K}$. Our study shows that the production yield of a spin 3/2 $\bar{D}^*Ξ_c$ state is approximately one order of magnitude larger than that of a spin $1/2$ state due to the interference of $\bar{D}_sΞ_c$ and $\bar{D}_s^*Ξ_c$ intermediate states. We obtain a model independent constraint on the product of couplings $g_{P_{cs}\bar{D}^*Ξ_c}$ and $g_{P_{cs}J/ψΛ}$. With the predictions of two particular molecular models as inputs, we calculate the branching ratio of $Ξ_b^-\to (P_{cs}\to)J/ψΛK^- $ and compare it with the experimental measurement. We further predict the lineshape of this decay which could be useful to future experimental studies.

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arXiv2021

Spin-parities of the $P_c(4440)$ and $P_c(4457)$ in the One-Boson-Exchange Model

The LHCb collaboration has recently observed three pentaquark peaks, the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$. They are very close to a pair of heavy baryon-meson thresholds, with the $P_c(4312)$ located $8.9\,{\rm MeV}$ below the $\bar{D} Σ_c$ threshold, and the $P_c(4440)$ and $P_c(4457)$ located $21.8$ and $4.8\,{\rm MeV}$ below the $\bar{D}^* Σ_c$ one. The spin-parities of these three states have not been measured yet. In this work we assume that the $P_c(4312)$ is a $J^P = \tfrac{1}{2}^{-}$ $\bar{D} Σ_c$ bound state, while the $P_c(4440)$ and $P_c(4457)$ are $\bar{D}^* Σ_c$ bound states of unknown spin-parity, where we notice that the consistent description of the three pentaquarks in the one-boson-exchange model can indeed determine the spin and parities of the later, i.e. of the two $\bar{D}^* Σ_c$ molecular candidates. For this determination we revisit first the one-boson-exchange model, which in its original formulation contains a short-range delta-like contribution in the spin-spin component of the potential. We argue that it is better to remove these delta-like contributions because, in this way, the one-boson-exchange potential will comply with the naive expectation that the form factors should not have a significant impact in the long-range part of the potential (in particular the one-pion-exchange part). Once this is done, we find that it is possible to consistently describe the three pentaquarks, to the point that the $P_c(4440)$ and $P_c(4457)$ can be predicted from the $P_c(4312)$ within a couple of MeV with respect to their experimental location. In addition the so-constructed one-boson-exchange model predicts the preferred quantum numbers of the $P_c(4440)$ and $P_c(4457)$ molecular pentaquarks to be $\tfrac{3}{2}^-$ and $\tfrac{1}{2}^-$, respectively.

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arXiv2021

Can the nature of $a_0(980)$ be tested in the $D_s^{+}\to π^{+}π^0 η$ decay?

From the amplitude analysis of the $D^+_s \to π^+ π^0 η$ decay, the BESIII Collaboration firstly observed the $D^+_s \to a_0(980)^+π^0$ and $D^+_s \to a_0(980)^0π^+$ decay modes, which are expected to occur through the pure $W$-annihilation processes. The measured branching fraction $\mathcal{B}[D_{s}^{+}\to a_{0}(980)^{+(0)}π^{0(+)},a_{0}(980)^{+(0)}\to π^{+(0)}η]$ is, however, found to be larger than those of known $W$-annihilation decays by one order of magnitude. This apparent contradiction can be reconciled if the two decays are induced by internal $W$-conversion or external $W$-emission mechanisms instead of $W$-annihilation mechanism. In this work, we propose that the $D^+_s$ decay proceeds via both the external and internal $W$-emission instead of $W$-annihilation mechanisms. In such a scenario, we perform a study of the $D^+_s \to π^+π^0η$ decay by taking into account the contributions from the tree diagram $D^+_s \to ρ^+ η\to π^+ π^0 η$ and the intermediate $ρ^+ η$ and $K^*\bar{K}/K\bar{K}^*$ triangle diagrams. The intermediate $a_0(980)$ state can be dynamically generated from the final state interactions of coupled $K \bar{K}$ and $πη$ channels, and it is shown that the experimental data can be described fairly well, which supports the interpretation of $a_0(980)$ as a molecular state.

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arXiv2021

Triply charmed dibaryons in the one boson exchange model

The pentaquark states, $P_{c}(4312)$, $P_{c}(4440)$ and $P_{c}(4450)$, can be nicely arranged into a multiplet of seven molecules of $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$ dictated by heavy quark spin symmetry, while the $Ξ_{cc}^{(\ast)}Σ_{c}^{(\ast)}$ system can be related to the $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$ system via heavy antiquark diquark symmetry. In this work we employ the one boson exchange model to study the interactions between $Ξ_{cc}^{(\ast)}$ and $Σ_{c}^{(\ast)}$ with constraints from the pentaquark system. We show that a multiplet of ten triply charmed dibaryons emerge naturally in the isospin-1/2 sector, while only three appear in the isospin-3/2 sector. In addition, we study their heavy quark flavor partners. Ten triply bottom diybaryons are found in the isospin-1/2 sector, while only nine are likely in the isospin-3/2 sector. Furthermore, the predicted mass splitting between the $0^{+}$ $Ξ_{cc}Σ_{c}$ state and its $1^{+}$ counterpart is found to be consistent with the correlation implied by heavy antiquark diquark symmetry recently pointed out in Pan $et$ $al$..

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arXiv2020

Heavy-hadron molecules from light-meson-exchange saturation

In the effective field theory framework the interaction between two heavy hadrons can be decomposed into a long- and a short-range piece. The long-range piece corresponds to the one-pion-exchange potential and is relatively well-known. The short-range piece is given by a series of contact-range interactions with unknown couplings, which substitute the less well-known short-range dynamics. While the general structure of the short-range potential between heavy hadrons is heavily constrained from heavy-quark symmetry, the couplings are still free parameters. Here we argue that the relative strength and the sign of these couplings can be estimated from the hypothesis that they are saturated by the exchange of light mesons, in particular the vector mesons $ρ$ and $ω$, i.e. from resonance saturation. However, we propose a novel saturation procedure that effectively removes form-factor artifacts. From this we can determine in which spin and isospin configurations the low-energy constants are most attractive for specific two-heavy-hadron systems. In general the molecular states with lower isospins and higher spins will be more attractive and thus more probable candidates to form heavy-hadron molecules. This pattern is compatible with the interpretation of the $X(3872)$ and $P_c(4312/4440/4457)$ as molecular states, but it is not applicable to states with maximum isospin like the $Z_c(3900/4020)$.

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arXiv2020

Is $X(7200)$ the heavy anti-quark diquark symmetry partner of $ X(3872)$?

The $D^{(\ast)}Ξ_{cc}^{(\ast)}$ system and $\barΞ_{cc}^{(\ast)}Ξ_{cc}^{(\ast)}$ system can be related to the $D^{(\ast)}\bar{D}^{(\ast)}$ system via heavy anti-quark di-quark symmetry (HADS). In this work, we employ a contact-range effective field theory to systematically investigate the likely existence of molecules in these systems in terms of the hypothesis that X(3872) is a $1^{++}$~$D\bar{D}^{\ast}$ bound state in the isospin symmetry limit, with some of the unknown low energy constants estimated using the light-meson saturation approximation. In the meson-meson system, a $J^{PC}=2^{++}$~$\bar{D}^{\ast}D^{\ast}$ molecule commonly referred to as $X(4013)$ is reproduced, which is the heavy quark spin partner of $X(3872)$. In the meson-baryon system, we predict two triply charmed pentaquark molecules, $J^{P}=1/2^{-}$~$D^{\ast}Ξ_{cc}$ and $J^{P}=5/2^{-}$~$D^{\ast}Ξ_{cc}^{\ast}$. In the baryon-baryon system, there exist seven di-baryon molecules, $J^{PC}=0^{-+}$~$\barΞ_{cc}Ξ_{cc}$, $J^{PC}=1^{--}$~$\barΞ_{cc}Ξ_{cc}$, $J^{PC}=1^{-+}$~$\barΞ_{cc}Ξ_{cc}^{\ast}$, $J^{PC}=1^{--}$~$\barΞ_{cc}Ξ_{cc}^{\ast}$, $J^{PC}=2^{-+}$~$\barΞ_{cc}Ξ_{cc}^{\ast}$, $J^{PC}=2^{-+}$~$\barΞ_{cc}^{\ast}Ξ_{cc}^{\ast}$ and $J^{PC}=3^{--}$~$\barΞ_{cc}^{\ast}Ξ_{cc}^{\ast}$. Among them, the $J^{PC}=0^{-+}$~$\barΞ_{cc}Ξ_{cc}$ and/or $J^{PC}=1^{--}$~$\barΞ_{cc}Ξ_{cc}$ molecules may contribute to the $X(7200)$ state recently observed by the LHCb Collaboration, which implies that $X(7200)$ can be related to $X(3872)$ via HADS. As a byproduct, with the heavy quark flavor symmetry we also study likely existence of molecular states in the $B^{(\ast)}\bar{B}^{(\ast)}$, $\bar{B}^{(\ast)}Ξ_{bb}^{(\ast)}$, and $\barΞ_{bb}^{(\ast)}Ξ_{bb}^{(\ast)}$ systems.

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arXiv2020

Excited $K$ meson, $K_c(4180)$, with hidden charm as a $D\bar{D}K$ bound state

Motivated by the recent discovery of two new states in the $B^+\rightarrow D^+D^-K^+$ decay by the LHCb Collaboration, we study the $D\bar{D}K$ three-body system by solving the Schrödinger equation with the Gaussian Expansion Method. We show that the $D\bar{D}K$ system can bind with quantum numbers $I(J^P)=\frac{1}{2}(0^-)$ and a binding energy of $B_3(D\bar{D}K)=48.9^{+1.4}_{-2.4}$ MeV. It can decay into $J/ψK$ and $D_s\bar{D}^*$ via triangle diagrams, yielding a partial decay width of about 1 MeV. As a result, if discovered, it will serve as a highly nontrivial check on the nature of the many exotic hadrons discovered so far and on non-perturbative QCD as well. Assuming heavy quark spin symmetry, the same formalism is applied to study the $D\bar{D}^*K$ system, which is shown to also bind with quantum numbers $I(J^P)=\frac{1}{2}(1^-)$ and a binding energy of $B_3(D\bar{D}^*K)\simeq 77.3^{+3.1}_{-6.6}$ MeV, consistent with the results of previous works.

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arXiv2020

Can $Z_{cs}(3985)$ be a molecular state of $\bar{D}_s^D$ and $\bar{D}_sD^$ ?

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, cannot be a pure hadronic molecular state of $\bar{D}_s D^*$ and $\bar{D}_s^*D$ and could consist of large components of compact nature.

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arXiv2020

Can discovery of hidden charm strange pentaquark states help determine the spins of $P_c(4440)$ and $P_c(4457)$?

The pentaquark states, $P_{c}(4312)$, $P_{c}(4440)$ and $P_{c}(4457)$, could be nicely arranged into a multiplet of seven molecules of $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$ dictated by heavy quark spin symmetry. However, the spins of $P_c(4440)$ and $P_c(4457)$ are not yet fully determined. In this work we employ the contact-range effective field theory to investigate the $SU(3)$-flavor counterparts of $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$, and study the possibility whether their discovery can help determine the spins of $P_c(4457)$ and $P_c(4440)$. We find the existence of a complete hidden charm strange multiplet of $\bar{D}^{(\ast)}Ξ_{c}^{(\prime\ast)}$ molecules irrespective of the spins of $P_c(4440)$ and $P_c(4457)$. On the other hand, we find that although molecules of $\bar{D}^{(\ast)}Ξ_{c}$ are also likely, depending on the realization of the underlying dynamics, their discovery can be more useful to determine the spins of $P_{c}(4440)$ and $P_{c}(4457)$ and to tell how the heavy quark and light quark interaction depends on the spin of the light quark pair.

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arXiv2020

$X_0(2866)$ as a $D^\bar{K}^$ molecular state

Very recently the LHCb Collaboration reported the discovery of two open charm tetraquark states, $X_{0}(2866)$ and $X_{1}(2904)$. In the present work, we study the $D^{(\ast)}$ and $\bar{K}^{(\ast)}$ interaction in the one-boson exchange model and show that the $X_{0}(2866)$ can be understood as a $D^{\ast}\bar{K}^{\ast}$ molecule with $I(J^{P})=0(0^{+})$, or at least it has a large molecular component. On the other hand, the $X_{1}(2904)$ can not be interpreted as a molecular state. Inspired by the discovery of the $X_0(2866)$ and the fact that the $D^*\bar{K}^*$ interaction is strong enough to generate a bound state, we also discuss likely existence of other open charm molecules. In the meson-meson sector, two molecules near the mass thresholds of $DD^{\ast}$ and $D^{\ast}D^{\ast}$ with $I(J^{P})=0(1^{+})$ are obtained, and using the heavy quark flavor symmetry their $\bar{B}\bar{B}^{\ast}$ and $\bar{B}^{\ast}\bar{B}^{\ast}$ counterparts are also predicted. In the meson-baryon sector, 7 open charm molecules with $I=1/2$ near the mass thresholds of $D^{(\ast)}Σ_{c}^{(\ast)}$ naturally appear, as dictated by the heavy quark spin symmetry.

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arXiv2020

Quadruply charmed baryons as heavy quark symmetry partners of the $D_{s0}^*(2317)$

Both unitary chiral theories and lattice QCD simulations show that the $DK$ interaction is attractive and can form a bound state, namely, $D^*_{s0}(2317)$. Assuming the validity of the heavy antiquark-diquark symmetry (HADS), the $Ξ_{cc}\bar{K}$ interaction is the same as the $DK$ interaction, which implies the existence of a $Ξ_{cc}\bar{K}$ bound state with a binding energy of $49-64$ MeV. In this work, we study whether a $Ξ_{cc}Ξ_{cc}\bar{K}$ three-body system binds. The $Ξ_{cc}Ξ_{cc}$ interaction is described by exchanging $π$, $σ$, $ρ$, and $ω$ mesons, with the corresponding couplings related to those of the $NN$ interaction via the quark model. We indeed find a $Ξ_{cc}Ξ_{cc}\bar{K}$ bound state, with quantum numbers $J^P=0^-$, $I=\frac{1}{2}$, $S=1$ and $C=4$, and a binding energy of $80-118$ MeV. It is interesting to note that this system is very similar to the well-known $NN\bar{K}$ system, which has been studied extensively both theoretically and experimentally. Within the same framework, we show the existence of a $NN\bar{K}$ state with a binding energy of $35-43$ MeV, consistent with the results of other theoretical works and experimental data, which serves as a consistency check on the predicted $Ξ_{cc}Ξ_{cc}\bar{K}$ bound state.

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arXiv2019

Strong decays of the explicitly exotic doubly charmed $DDK$ bound state

Nowadays, it is generally accepted that the $DK$ interaction in isospin zero is strongly attractive and the $D_{s0}^*(2317)$ can be described as a $DK$ molecular state. Recent studies show that the three-body $DDK$ system binds as well with a binding energy about 60$\sim$70 MeV. The $DDK$ bound state has isospin $1/2$ and spin-parity $0^-$. If discovered either experimentally or in lattice QCD, it will not only provide further support on the molecular nature of the $D_{s0}^*(2317)$, but also provide a way to understand other exotic hadrons expected to be of molecular nature. In the present work, we study its two-body strong decay widths via triangle diagrams. We find that the partial decay width into $DD_sπ$ is at the order of $2\sim3$ MeV, which seems to be within the reach of the current experiments such as BelleII. As a result, we strongly recommend this decay channel of the $DDK$ bound state to be searched for experimentally.

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