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Inspired by the observation of the $P_{cs} (4459)$ state by LHCb recently, we reexamine the results of the interaction of the $J/psi Lambda$ channel with its coupled channels, exploiting the coupled channel unitary approach combined with heavy quark spin and local hidden gauge symmetries. By tuning the only free parameter, we find a pole of $(4459.07+i6.89)$ MeV below the $bar D^* Xi_c$ threshold, which was consistent well with the mass and width of the $P_{cs} (4459)$ state. Thus, we assume the $P_{cs} (4459)$ state to be a $bar D^* Xi_c$ bound state with the uncertainties on its degeneracy with $J^P = frac{1}{2}^-$ and $J^P = frac{3}{2}^-$. For the degeneracy, it would have two-poles structure, like $P_c (4450)$ before. There is another pole in the $J^P = frac{1}{2}^-$ sector, $(4310.53+i8.23)$ MeV, corresponding to a deep bound state of $bar D Xi_c$. Furthermore, the previously predicted loose bound states of $bar D Xi_c$, $bar D^* Xi_c$, $bar D^* Xi^*_c$ with $J=1/2,~I=0$ and $bar D^* Xi_c$, $bar D Xi^*_c$, $bar D^* Xi_c^*$ with $J=3/2,~I=0$ may exist as either bound states or unbound virtual states. We hope that future experiments can search for the $bar D^{(*)} Xi_c$ molecular states in their dominant decay channels of $bar D^{(*)}_s Lambda_c$, also in the $J/psi Lambda$ and $eta_c Lambda$ channels to reveal their different nature.
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Recently, the LHCb Collaboration reported a new structure $P_{cs}(4459)$ with a mass of 19 MeV below the $Xi_c bar{D}^{*} $ threshold. It may be a candidate of molecular state from the $Xi_c bar{D}^{*} $ interaction. In the current work, we perform a coupled-channel study of the $Xi_c^*bar{D}^*$, $Xi_cbar{D}^*$, $Xi^*_cbar{D}$, $Xi_cbar{D}^*$, $Xi_cbar{D}$, and $Xi_cbar{D}$ 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 $Xi_c bar{D}^{*} $ molecular states are produced with spin parities $ J^P=1/2^-$ and $3/2^- $. The lower state with $3/2^-$ can be related to the observed $P_{cs}(4450)$ while two-peak structure can not be excluded. Within the same model, other strange hidden-charm pentaquarks are also predicted. Two states with spin parities $1/2^-$ and $3/2^-$ are predicted near the $Xi_cbar{D}$, $Xi_cbar{D}$, and $Xi_c^*bar{D}$ thresholds, respectively. As two states near $Xi_c bar{D}^{*}$ threshold, two states are produced with $1/2^-$ and $3/2^-$ near the $Xi_cbar{D}^*$ threshold. The couplings of the molecular states to the considered channels are also discussed. The experimental research of those states are helpful to understand the origin and internal structure of the $P_{cs}$ and $P_c$ states.
In this work, we study the strong decay of the newly observed $P_{cs}(4459)$ assuming that it is a pure $Xi_cbar{D}^{*}$ molecular state. Considering two possible spin-parity assignments $J^P=1/2^{-}$ and $J^P=3/2^{-}$ the partial decay widths of the $Xi_cbar{D}^{*}$ molecular state into $J/psi{}Lambda$, $D_s^{-}Lambda_c^{+}$, and $DXi_c^{()}$ final states through hadronic loops are evaluated with the help of the effective Lagrangians. In comparison with the LHCb data, the spin-party $J^P=1/2^{-}$ the assignment is preferred while this of $J^P=3/2^{-}$ is disfavored. The $P_{cs}(4459)$ in spin-parity $J^P=3/2^{-}$ case maybe explained as $S$-wave coupled bound state with lager $Xi_cbar{D}^{*}$ component. In addition, the calculated partial decay widths with $J^P=1/2^{-}$ $Xi_cbar{D}^{*}$ molecular state picture indicates that allowed decay mode, $DXi_c^{}$, may have the biggest branching ratio. The experimental measurements for this strong decay process could be a crucial test for the molecule interpretation of the $P_{cs}(4459)$.
In this letter, we propose interpolating currents for the X(3872) resonance, and show that, in the Heavy Quark limit of QCD, the X(3872) state should have degenerate partners, independent of its internal structure. Magnitudes of possible I=0 and I=1 components of the X(3872) are also discussed.
In this work, an Effective Field Theory (EFT) incorporating light SU(3)-flavour and heavy quark spin symmetry is used to describe charmed meson-antimeson bound states. At Lowest Order (LO), this means that only contact range interactions among the heavy meson and antimeson fields are involved. Besides, the isospin violating decays of the X(3872) will be used to constrain the interaction between the $D$ and a $bar{D}^*$ mesons in the isovector channel. Finally, assuming that the X(3915) and Y(4140) resonances are $D^*bar{D}^*$ and $D_s^*bar{D}_s^*$ molecular states, we can determine the four Low Energy Constants (LECs) of the EFT that appear at LO and, therefore, the full spectrum of molecular states with isospin I=0, 1/2 and 1.
Recently, the LHCb Collaboration reported on the evidence for a hidden charm pentaquark state with strangeness, i.e., $P_{cs}(4459)$, in the $J/psiLambda$ invariant mass distribution of the $Xi_b^-to J/psi Lambda K^-$ decay. In this work, assuming that $P_{cs}(4459)$ is a $bar{D}^*Xi_c$ molecular state, we study this decay via triangle diagrams $Xi_brightarrow bar{D}_s^{(*)}Xi_cto (bar{D}^{(*)}bar{K})Xi_cto P_{cs} bar{K}to (J/psiLambda) bar{K}$. Our study shows that the production yield of a spin 3/2 $bar{D}^*Xi_c$ state is approximately one order of magnitude larger than that of a spin $1/2$ state due to the interference of $bar{D}_sXi_c$ and $bar{D}_s^*Xi_c$ intermediate states. We obtain a model independent constraint on the product of couplings $g_{P_{cs}bar{D}^*Xi_c}$ and $g_{P_{cs}J/psiLambda}$. With the predictions of two particular molecular models as inputs, we calculate the branching ratio of $Xi_b^-to (P_{cs}to)J/psiLambda K^- $ 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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