“…The discovery of the T ++ cc inspired many related studies [33][34][35][36][37][38][39][40][41]. Actually, the doubly heavy tetraquarks have been studied extensively in the literature, with models like the quark model [1,, QCD sum rules [69][70][71][72][73][74][75][76], Lattice QCD [77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95], the OBE potentials [32,[96][97][98], chiral perturbation theory [99][100][101], etc. The studies suggest that the masses of some of the doubly heavy tetraquarks are lighter than the thresholds of two mesons, which makes them stable against the strong and electromagnetic decays.…”