Hidden-charm tetraquarks with strangeness in the chiral quark model

The hidden-charm tetraquarks with strangeness, cc over bar sq over bar (q = u, d), in JP = 0+, 1+, and 2+ are systematically investigated in the framework of real- and complex-scaling range of a chiral quark model, whose parameters have been fixed in advance describing hadron, hadron-hadron, and multiquark phenomenology. Each tetraquark configuration, compatible with the quantum numbers studied, is taken into account; this includes meson-meson, diquark-antidiquark, and K-type arrangements of quarks with all possible color wave functions in the four-body sector. Among the different numerical techniques to solve the Schrodinger-like four-body bound state equation, we use a variational method in which the trial wave function is expanded in complex-range Gaussian basis functions, which is characterized by its simplicity and flexibility. This theoretical framework has already been used to study different kinds of multiquark systems, such as the hidden-charm pentaquarks P+c and doubly charmed tetraquarks T+cc. The recently reported Zcs states by the BESIII and LHCb Collaborations could be associated, in our investigation, with either compact tetraquark or hadronic molecular resonance configurations. However, it is fair to recognize that our complex poles survive when either the (cc over bar )(sq over bar ) or (cq over bar )(sc over bar ) configuration is preserved, but most of them get diluted when both are considered at the same time, indicating that such states seem to be very unstable. Finally, we mention that similar types of structures are also found in the mass range between 3.8 and 4.6 GeV.

Automated summary

The study systematically investigates hidden-charm tetraquarks with strangeness in the framework of a chiral quark model and considers different quark configurations and color wave functions. A variational method using complex-range Gaussian basis functions is used to solve the four-body bound state equation, showing that the states seem to be very unstable.