We use QCD sum rules to study the possible existence of $QQ-\bar{ u}\bar{ d}$ mesons, assumed to be a state with $J^{ P}=1^{ +}$. For definiteness, we work with a current with an axial heavy diquark and a scalar light antidiquark, at leading order in $\alpha_s$. We consider the contributions of condensates up to dimension eight. For the $b$-quark, we predict $M_{ T_{ bb}}= (10.2\pm 0.3) { \rm GeV}$, which is below the $\bar{ B}\bar{ B}^*$ threshold. For the $c$-quark, we predict $M_{ T_{ cc}}= (4.0\pm 0.2) { \rm GeV}$, in agreement with quark model predictions.
Categories: hep-ph