Inclusion of heavy spin effects in the $ud\bar{b}\bar{b}$ $I(J^P)=0(1^{-})$ four-quark channel in the Born-Oppenheimer approximation

We refine our previous study of a $ud\bar{b}\bar{b}$ tetraquark resonance with quantum numbers $I(J^P)=0(1^{-})$, which is based on antiheavy-antiheavy lattice QCD potentials, by including heavy quark spin effects via the mass difference of the $B$ and the $B^{\ast }$ meson. This leads to a coupled channel Schrödinger equation, where the two channels correspond to $BB$ and $B^{\ast }{B}^{\ast }$, respectively. We search for $T$ matrix poles in the complex energy plane, but do not find any indication for the existence of a tetraquark resonance in this refined coupled channel approach. We also vary the antiheavy-antiheavy potentials as well as the $b$ quark mass to further understand the dynamics of this four-quark system.