LAUSR

Symmetries play important roles in the understanding of hadron structures and spectroscopy. Motivated by the discovery of the doubly charmed tetraquark $T_{cc}^+(3875)$, we study the ground states of the doubly heavy tetraquarks with the QCD inspired heavy antiquark-diquark symmetry in the constituent quark model. Six ground states of $T_{QQ} (Q=c,b)$ are predicted and the lightest $T_{cc}$ state has a mass of $3875.8\pm 7.6$ MeV and spin-parity $1^+$ which are consistent with those of the observed $T_{cc}^+(3875)$. In addition, the magnetic moments of the predicted tetraquarks $T_{cc}^+(3876)$ and $T_{bb}^-(10396)$ are also estimated in the same model, which provide further informations to distinguish the structures of the $T_{QQ}$ states. Our results show that the heavy antiquark-diquark symmetry conserves well in these doubly heavy tetraquarks in both the spectrum and magnetic moment perspectives.