Full-heavy tetraquarks in constituent quark models

The full-heavy tetraquarks $$bb{\bar{b}}{\bar{b}}$$ and $$cc{\bar{c}}{\bar{c}}$$ are systematically investigated within the chiral quark model and the quark delocalization color screening model. Two structures, meson–meson and diquark–antidiquark, are considered. For the full-beauty $$bb{\bar{b}}{\bar{b}}$$ systems, there is no any bound state or resonance state in two structures in the chiral quark model, while the wide resonances with masses around $$19.1-19.4$$ GeV and the quantum numbers $$J^{P}=0^{+}$$, $$1^{+}$$, and $$2^{+}$$ are possible in the quark delocalization color screening model. For the full-charm $$cc{\bar{c}}{\bar{c}}$$ systems, the results are qualitative consistent in two quark models. No bound state can be found in the meson–meson configuration, while in the diquark–antidiquark configuration there may exist the resonance states, with masses range between 6.2 to 7.4 GeV, and the quantum numbers $$J^{P}=0^{+}$$, $$1^{+}$$, and $$2^{+}$$. And the separation between the diquark and the antidiquark indicates that these states may be the compact resonance states. The reported state X(6900) is possible to be explained as a compact resonance state with $$IJ^{P}=00^{+}$$ in present calculation. All these full-charm resonance states are worth searching in the experiments further