Double-heavy tetraquark states with heavy diquark-antiquark symmetry *

We calculate the masses of $QQ\bar{q}\bar{q}$ ($Q=c,b$; $q=u,d,s$) tetraquark states with aid heavy diquark-antiquark symmetry (HDAS) and chromomagnetic interaction (CMI) model. The highest-spin ($J=2$) tetraquarks that have only $(QQ)_{\bar{3}_c}(\bar{q}\bar{q})_{3_c}$ color structure are related those conventional hadrons using HDAS. Thereafter, their partner determined mass splittings in CMI Our numerical results reveal that: (i) lightest $cc\bar{n}\bar{n}$ ($n=u,d$) is an $I(J^P)=0(1^+)$ state around 3929 MeV (53 above $DD^*$ threshold) none double-charm stable; (ii) stable double-bottom lowest $0(1^+)$ $bb\bar{n}\bar{n}$ 10488 ($\approx116$ below $BB^*$ $1/2(1^+)$ $bb\bar{n}\bar{s}$ 10671 ($\approx20$ $BB_s^*/B_sB^*$ threshold); (iii) two $bc\bar{n}\bar{n}$ tetraquarks, namely $0(0^+)$ 7167 7223 MeV, near-threshold states. Moreover, we discuss constraints on double-heavy hadrons. Specifically, for nonstrange obtain $T_{cc}<3965$ $T_{bb}<10627$ $T_{bc}<7199$ MeV.