Spectrum of the S-wave fully-heavy tetraquark states

In present work, spectrum of the $S$-wave fully-heavy tetraquark states $QQ\bar{Q}\bar{Q}$ ($Q=c,b$), i.e., $cc\bar{c}\bar{c}$, $bb\bar{b}\bar{b}$, $cc\bar{b}\bar{b}$/$bb\bar{c}\bar{c}$, $bc\bar{c}\bar{c}$/ $cc\bar{b}\bar{c}$, $bb\bar{c}\bar{b}$/$cb\bar{b}\bar{b}$, and $bc\bar{b}\bar{c}$ are systematically investigated within an nonrelativistic constituent quark model, in which Instanton-induced one-gluon-exchange interactions taken into account as residual spin-dependent hyperfine interaction. Our results show that with $cc\bar{c}\bar{c}$ $bb\bar{b}\bar{b}$ components could be located around $ 6500$ MeV 19200$ MeV, respectively. Based on our calculations, new $X(6900)$ state observed by LHCb may not a ground state, while it orbitally or radially excited system. On other hand, recently reported $X(6600)$ CMS ATLAS can explained spin-parity $J^{PC} =0^{++}$.