Mass spectra of hidden heavy-flavor tetraquarks with two and four heavy quarks

Ting-Qi Yan, Wen-Xuan Zhang, Duojie Jia

Inspired by the observation of the $X(6900)$ by LHCb and the $X(6600)$ (with mass $6552\pm 10$ $\pm 12$ MeV) recently by CMS and ATLAS experiments of the LHC in the di-$J/\Psi$ invari…