Triply heavy tetraquark states

In the framework of an extended chromomagnetic model, we systematically study mass spectrum $S$-wave $qQ\bar{Q}\bar{Q}$ tetraquarks. Their spectra are mainly determined by color interaction. For $qc\bar{c}\bar{c}$, $qb\bar{c}\bar{c}$ and $qb\bar{b}\bar{b}$ tetraquarks, interaction favors color-sextet $\ket{(qQ)^{6_{c}}(\bar{Q}\bar{Q})^{\bar{6}_{c}}}$ configuration over color-triplet $\ket{(qQ)^{\bar{3}_{c}}(\bar{Q}\bar{Q})^{3_{c}}}$ one. But for $qc\bar{b}\bar{b}$ is favored. We find no stable states which lie below thresholds two pseudoscalar mesons. The lowest axial-vector with $qQ\bar{b}\bar{b}$ flavor may be narrow. They just above mesons, but cannot decay into these channels because conservation angular momentum parity.