QQ Four-Quark Bound States in Chiral SU(3) Quark Model

The possibility of QQ heavy-light four-quark bound states has been analyzed by means of the chiral SU(3) quark model, where Q is the heavy quark (c or b) and q is the light quark (u, d, or s). We obtain a bound state for the bb configuration with quantum number J^P = 1⁺, I = 0 and for the cc (J^P = 1⁺, I = 0) configuration, which is not bound but slightly above the D^*D^* threshold (n is u or d quark). Meanwhile, we also conclude that a weakly bound state in bb system can also be found without considering the chiral quark interactions between the two light quarks, yet its binding energy is weaker than that with the chiral quark interactions.