Abstract
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.
Highlights
We investigate the full-heavy tetraquarks within two quark models: chiral quark model (ChQM) and quark delocalization color screening model (QDCSM)
For the tetraquarks composed of bbbb, the energies of the possible quantum numbers with two structures in both ChQM and QDCSM are listed in Tables 2 and 3, respectively
In the ChQM, the confinement does not contribute to the effective potential between bband bb, but it provides a slight repulsion in QDCSM
Summary
The LHCb collaboration observed the structure in the J/ψ−pair mass spectrum, and found a narrow structure X (6900), matching the lineshape of a resonance and a broad structure next to the di − J/ψ mass threshold [13] Such a breakthrough offers more information for the searching of the tetraquark consisting of four charm quarks. Wei Chen et al studied the existence of exotic doubly hidden-charm/bottom tetraquark states made of four heavy quarks in a moment QCD sum rule method and discovered that the masses of the bbbbtetraquarks are all below or very close to the thresholds of Υ(1S)Υ(1S) and ηb(1S)ηb(1S), except one current of J PC = 0++ and the masses of the cccctetraquarks are all above the threshold [22].
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