XVIII International Conference on Hadron Spectroscopy and Structure (HADRON2019)

A detailed study is presented of the flavor-exotic isoscalar $T_{bb}^-\equiv b b \bar u \bar d$ tetraquark. with spin and parity $J^P=1^+$. In realistic quark models, with a careful treatment of the 4-body problem, the $T_{bb}^-$ is approximately $150\,$MeV below the strong decay threshold $B^-\bar {B^*}^{0}$ and $105\,$MeV below the electromagnetic decay threshold $B^- \bar B^0 \gamma$. The lifetime of $T_{bb}$ is estimated, as well as the dominant decay modes where the tetraquark might be looked for in future experiments. Its total decay width is $\Gamma \simeq 79. \times 10^{-15}\,$GeV and therefore its lifetime $\tau \simeq 8.3\,$ps. The promising final states are ${B^*}^{-}\, {D^*}^{+} \, l^- \, \bar \nu_l$ and $\bar {B^*}^{0} \, {D^*}^{0} \, l^- \, \bar \nu_l $ among the semileptonic decays, and, among the non-leptonic ones, ${B^*}^{-} \, {D^*}^{+} \, {D_s^*}^-$, $\bar {B^*}^{0} \, {D^*}^{0} \, {D_s^*}^- $ ${B^*}^{-} \, {D^*}^{+} \, \rho^-$.