Resonance $X(5568)$ as an exotic axial-vector state
  The mass and meson-current coupling constant of the resonance $X(5568)$, as well as the width of the decay $X(5568)\to B_s^{\ast}\pi$ are calculated by modeling the exotic $X(5568)$ resonance as a diquark-antidiquark state $% X_b=[su][bd]$ with quantum numbers $J^{P}=1^{+}$. The calculations are made employing QCD two-point sum rule method, where the quark, gluon and mixed vacuum condensates up to dimension eight are taken into account. The sum rule approach on the light-cone in its soft-meson approximation is used to explore the vertex $X_bB_{s}^{\ast}\pi$ and extract the strong coupling $% g_{X_bB_{s}^{\ast}\pi}$, which is a necessary ingredient to find the width of the $X_b \to B_s^{\ast}\pi^{+}$ decay process. The obtained predictions are compared with the experimental data of the D0 Collaboration, and results of other theoretical works. 
S. S. Agaev, K. Azizi, B. Barsbay, H. Sundu
hep-ph