Bsπ-B(K)over-bar interactions in finite volume and X(5568)

The recent observation of X(5568) by the D0 Collaboration has aroused a lot of interest both theoretically and experimentally. In the present work, we first point out that X (5568) and D-s0* (2317) cannot simultaneously be of molecular nature, from the perspective of heavy-quark symmetry and chiral symmetry, based on a previous study of the lattice QCD scattering lengths of DK and its coupled channels. Then we compute the discrete energy levels of the B-s pi and B (K) over bar system in finite volume using unitary chiral perturbation theory. The comparison with the latest lattice QCD simulation, which disfavors the existence of X(5568), supports our picture where the B-s pi and B (K) over bar interactions are weak and X (5568) cannot be a B-s pi and B (K) over bar molecular state. In addition, we show that the extended Weinberg compositeness condition also indicates that X (5568) cannot be a molecular state made from B-s pi and B (K) over bar interactions.