Stable scalar tetraquark $$T_{bb;\bar{u}\bar{d}}^{-}$$

Abstract

The mass and coupling of the scalar tetraquark $T_{bb;\overline{u}\overline{d }}^{-}$ (hereafter $T_{b:\overline{d}}^{-} $) are calculated in the context of the QCD two-point sum rule method. In computations we take into account effects of various quark, gluon and mixed condensates up to dimension ten. The result obtained for the mass of this state $m=(10135\pm 240)~\mathrm{MeV} $ demonstrates that it is stable against the strong and electromagnetic decays. We also explore the dominant semileptonic $T_{b:\overline{d}}^{-} \to \widetilde{Z}_{bc;\bar{u}\bar{d}}^{0}l\overline{\nu }_{l}$ and nonleptonic decays $T_{b:\overline{d}}^{-} \to \widetilde{Z}_{bc;\bar{u}\bar{ d}}^{0}M$, where $\widetilde{Z}_{bc;\bar{u}\bar{d}}^{0}$ is the scalar tetraquark composed of color-sextet diquark and antidiquark, and $M$ is one of the final-state pseudoscalar mesons $\pi^{-}, K^{-}, D^{-}$ and $D_s^{-}$ , respectively. The partial widths of these processes are calculated in terms of the weak form factors $G_{1(2)}(q^2)$, which are determined from the QCD three-point sum rules. Predictions for the mass, full width $\Gamma _{\mathrm{full}} =(10.88\pm 1.88)\times 10^{-10}~\mathrm{MeV}$, and mean lifetime $\tau=0.61_{-0.09}^{+0.13}~\mathrm{ps}$ of the $T_{b:\overline{d} }^{-}$ obtained in the present work can be used in theoretical and experimental studies of this exotic state.