Hidden-charm pentaquarks with strangeness in a chiral quark model

Abstract

The LHCb collaboration has recently announced the discovery of two hidden-charm pentaquark states with also strange quark content, $P_{cs}(4338)$ and $P_{cs}(4459)$; its analysis points towards having both hadrons isospin equal to zero and spin-parity quantum numbers ${\frac{1}{2}}^{-}$ and ${\frac{3}{2}}^{-}$, respectively. We perform herein a systematical investigation of the $qqsc\bar{c}$ $(q=u,d)$ system by means of a chiral quark model, along with a highly accurate computational method, the Gaussian expansion approach combined with the complex-scaling technique. Baryon-meson configurations in both singlet- and hidden-color channels are considered. The $P_{cs}(4338)$ and $P_{cs}(4459)$ signals can be well identified as molecular bound states with dominant components $\Lambda J/\psi$ $(60\%)$ and ${\Xi }_{c}D$ $(23\%)$ for the lowest-energy case and ${\Xi }_c{D}^{\ast }$ $(72\%)$ for the highest-energy one. Besides, it seems that some narrow resonances can be also found in each allowed $I(J^P)$-channel in the energy region of $4.6-5.5$ GeV, except for the $1({\frac{1}{2}}^{-})$ where a shallow bound state with dominant ${\Xi }_c^{\ast }{D}^{\ast }$ structure is obtained at $4673$ MeV with binding energy $E_B=-3$ MeV. These exotic states are expected to be confirmed in future high energy experiments.

16 pages, 16 tables and 7 figures