Weak decays of the axial-vector tetraquark $T_{bb;\bar{u} \bar{d}}^{-}$

Abstract: The weak decays of the axial-vector tetraquark $T_{bb;\bar{u} \bar{d}}^{-}$ to the scalar state $Z_{bc;\bar{u} \bar{d}}^{0}$ are investigated using the QCD three-point sum rule approach. In order to explore the process $T_{bb; \bar{u} \bar{d}}^{-} \to Z_{bc;\bar{u} \bar{d}}^{0}l \bar{\nu_l}$, we recalculate the spectroscopic parameters of the tetraquark $T_{bb;\bar{u} \bar{d}}^{-}$ and find the mass and coupling of the scalar four-quark system $Z_{bc;\bar{u} \bar{d}}^{0}$, 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 $T_{bb;\bar{u} \bar{ d}}^{-}$ state is found to be $m=(10035~\pm 260)~\mathrm{MeV}$, which demonstrates that it is stable against the strong and electromagnetic decays. The full width $\Gamma$ and mean lifetime $\tau$ of $T_{bb;\bar{u} \bar{d} }^{-}$ are evaluated using its semileptonic decay channels $T_{bb; \bar{u} \bar{d}}^{-} \to Z_{bc;\bar{u} \bar{d}}^{0}l \bar{\nu_l}$, $l=e,\mu$ and $\tau$. The obtained results, $\Gamma=(7.17\pm 1.23)\times 10^{-8\ \ } \mathrm{MeV}$ and $\tau =9.18_{-1.34}^{+1.90}~\mathrm{fs}$, can be useful for experimental investigations of the doubly-heavy tetraquarks.