Systematics of doubly heavy tetraquarks: nonstrange and strange

Masses, magnetic moments and color-spin structures of nonstrange and strange tetraquarks with two heavy quarks are systematically studied in QCD string picture with chromomagnetic interaction. Our mass computations combined with weak and radiative decays indicate that there are two doubly-heavy tetraquarks, the bottom-charmed tetraquark Tcb(7173,01⁺)⁰ and the doubly-bottom tetraquark Tbb(10406,01⁺)⁻, to be stable against the strong decay, having the lifetimes of $0.069$ fs and $326$ fs, respectively. Magnetic moments are also computed and found to be sensitive to chromomagnetic mixing of the color-spin configurations of these tetraquarks, being valuable probe to experimentally detect the nontrivial color configuration 6c⊗6̄c.