Lattice QCD investigation of a b-bar b-bar u d tetraquark resonance

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Our main objective is to study the existence and to determine mass and width of a b-bar b-bar u d tetraquark resonance with quantum numbers I(J^P) = 0(1^−) using lattice QCD. In previous work based on lattice QCD potentials and the Born-Oppenheimer approximation we found indication for the existence of such a resonance. There, however, several approximations have been used, in particular the b-bar quarks have been considered as infinitely heavy and the light and heavy degrees of freedom have been treated separately. Since b-bar quarks of finite mass are expected to weaken binding of the four-quark system, it is important and interesting to perform a full lattice QCD computation, where such approximations are not employed. Such a computation will provide further insights concerning heavy-heavy-light-light tetraquarks, a topic which received considerable interest in recent years, in particular due to the experimental discovery of the electrically charged Z_c and Z_b tetraquark states.