Systematics of fully heavy tetraquarks

In this work, we systematically study the mass spectrum of fully heavy tetraquark in an extended chromomagnetic model, which includes both color and interactions. Numerical results indicate that energy level is mainly determined by interaction, favors color-sextet $|(QQ{)}^{{6}_{c}}(\overline{Q}\overline{Q}{)}^{{\overline{6}}_{c}}?$ configuration over color-triplet $|(QQ{)}^{{\overline{3}}_{c}}(\overline{Q}\overline{Q}{)}^{{3}_{c}}?$ one. The interaction mixes two configurations gives small splitting. ground state always dominated configuration. We find no stable below lowest quarkonium pair thresholds. Most states may be wide since they have at least one $S$-wave decay channel into mesons. One possible narrow ${1}^{+}$ $bb\overline{b}\overline{c}$ with a 15719.1 MeV. It just above ${\ensuremath{\eta}}_{b}{\overline{B}}_{c}$ threshold. But forbidden because conservation angular momentum parity.