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Register a new userUnderstanding $P_{cs}(4459)$ as a hadronic molecule in the $Xi_b^-to J/psi Lambda K^-$ decay
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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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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 $P_{cs}(4459)$.
We investigate the production of the hidden-charm pentaquark $P_{cs}^0(4459)$ with strangeness in the $K^- p to J/psi Lambda$ reaction, employing two different theoretical frameworks, i.e., the effective Lagrangian method and the Regge approach. Having determined all relevant coupling constants, we are able to compute the total and differential cross sections for the $K^- p to J/psi Lambda$ reaction. We examine the contributions of $P_{cs}$ with different sets of spin-parity quantum number assigned. The present results may give a guide for possible future experiments.
We analyze possible singularities in the $J/psi Lambda$ invariant mass distribution of the $Xi^-_{b}~to~K^- J/psi Lambda$ process via triangle loop diagrams. Triangle singularities in the physical region are found in 18 different triangle loop diagrams. Among those with $Xi^*$-charmonium-$Lambda$ intermediate states, the one from the $chi_{c1} Xi(2120) Lambda$ loop, which is located around 4628 MeV, is found the most likely to cause observable effects. One needs $S$- and $P$-waves in $chi_{c1} Lambda$ and $J/psi Lambda$ systems, respectively, when the quantum numbers of these systems are $1/2^+$ or $3/2^+$. When the quantum numbers of the $Xi(2120)$ are $J^P=1/2^+$, $1/2^-$ or $3/2^+$, the peak structure should be sharper than the other $J^P$ choices. This suggests that although the whole strength is unknown, we should pay attention to the contributions from the $Xi^*$-charmonium-$Lambda$ triangle diagram if structures are observed in the $J/psi Lambda$ invariant mass spectrum experimentally. In addition, a few triangle diagrams with the $D_{s1}^*(2700)$ as one of the intermediate particles can also produce singularities in the $J/psiLambda$ distribution, but at higher energies above 4.9 GeV.
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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