A family of double-beauty tetraquarks: Axial-vector state ■

The spectroscopic parameters and decay channels of the axial-vector tetraquark ■(in what follows,■ are explored using the quantum chromodynamics(QCD) sum rule method.The mass and coupling of this state are calculated using two-point sum rules by taking into account various vacuum condensates,up to 10 dimensions.Our prediction for the mass of this state m=(10215±250) MeV confirms that it is stable with respect to strong and electromagnetic decays and can dissociate to conventional mesons only via weak transformations.We investigate the dominant semileptonic ■ and nonleptonic ■ decays of ■.In these processes,■ is a scalar tetraquark ■ built of a color-triplet diquark and an antidiquark,whereas M is one of the vector mesons ρ~-,K~*(892),D~*(2010)~-,and D_s~(*-).To calculate the partial widths of these decays,we use the QCD three-point sum rule approach and evaluate the weak transition form factors G_i(i=0,1,2,3),which govern these processes.The full width Γ_(full)=(12.9±2.1) × 10~(-8) MeV and the mean lifetime τ=5.1+_(-0.71) ~(+0.99) fs of the tetraquark ■ are computed using the aforementioned weak decays.The obtained information about the parameters of ■ and ■ is useful for experimental investigations of these double-heavy exotic mesons.