The exotic hadron states in quenched and unquenched quark models

Abstract

In recent two decades, a large number of exotic hadron states have been observed in experiments, which arouses great attentions in hadron physics community. In this short review, we briefly summarize progresses of our group on several exotic hadron states. Two approaches, quenched and unquenched quark models, are adopted in the calculation. The channel coupling effects, the multiquark states couple to open-channels and the quark-antiquark states couple to meson-meson states, are emphasized. X(3872) is showed to be a mixture state of ccbar and DDbar* in the unquenched quark model. X(2900) can be explained as a resonance state Dbar*K* with the quantum numbers IJP=00+ in both the quark delocalization color screening model and the chiral quark model. The reported state X(6900) can be explained as a compact resonance state with IJP=00+ in both two quark models, and several fully heavy tetraquark states are predicated. The possible hidden-charm pentaquarks are systematically investigated in QDCSM, and seven resonance states are obtained in the corresponding baryon-meson scattering process, among which the Σ_cD with JP=1/2-, Σ_cD* with JP=3/2- and JP=1/2- are consistent with the experimental report of Pc(4312), Pc(4440), and Pc(4457), respectively. Experimental search for more exotic hadron states will provide more information for understanding the exotic hadron states in quark models.