Doubly-heavy tetraquark states and *

Abstract Inspired by the recent observation of a very narrow state, called , LHCb collaboration, possible bound states and low-lying resonance doubly-heavy tetraquark cc\bar{u}\bar{d} ( T_{cc} ) bb\bar{u}\bar{d} T_{bb} are searched in framework chiral quark model with an accurate few-body method, Gaussian expansion method. The real scaling method is also applied to identify genuine states. In calculation, meson–meson structure, diquark–antidiquark their coupling all considered. numerical results show: (i) For only I(J^P) = 0(1^+) different structures. binding energy varies from few MeV for structure over 100 structure. example, there exists weakly molecule DD^* state around 3841.4 MeV, 1.8 below D^0D^{*+} which may be good candidate observed LHCb; however deeper mass 3700.9 obtained. When considering mixing, system decreases 3660.7 shallow disappears. (ii) Besides states, several T_{QQ}(Q c, b) 1(0^+), 1(1^+), 1(2^+), proposed.