Weak decays of the axial-vector tetraquark Tbb;(u)over-bar(d)over-bar-

The weak decays of the axial-vector tetraquark T-bb;(u) over bar(d) over bar(-) to the scalar state Z(bc;(u) over bar(d) over bar)(0) are investigated using the QCD three-point sum rule approach. In order to explore the process T-bb;(u) over bar(d) over bar(-) -> Z(bc;(u) over bar(d) over bar)(0)l (nu) over bar (l), we recalculate the spectroscopic parameters of the tetraquark T-bb;(u) over bar(d) over bar(-) and find the mass and coupling of the scalar four-quark system Z(bc;(u) over bar(d) over bar)(0), which are important ingredients of calculations. The spectroscopic parameters of these tetraquarks are computed in the framework of the QCD two-point sum rule method by taking into account various condensates up to dimension ten. The mass of the T-bb;(u) over bar(d) over bar(-) state is found to be m = (10035 +/- 260) MeV, which demonstrates that it is stable against the strong and electromagnetic decays. The full width Gamma and mean lifetime tau of T-bb;(u) over bar(d) over bar(-) are evaluated using its semileptonic decay channels T-bb;(u) over bar(d) over bar(-) -> Z(bc;(u) over bar(d) over bar)(0)l (nu) over bar (l), l = e, mu, and tau. The obtained results, Gamma = (7.17 +/- 1.23) x 10(-8) MeV and tau = 9.18(-1.34)(+1.90) fs, can be useful for experimental investigations of the doubly-heavy tetraquarks.