Abstract
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_spi and Bbar{K} 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_spi and Bbar{K} interactions are weak and X(5568) cannot be a B_spi and Bbar{K} 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_spi and Bbar{K} interactions.
Highlights
An apparently exotic mesonic state, the so-called X (5568) state, was observed by the D0 Collaboration in the Bs0π ± invariant mass spectrum [1]
Ds∗0(2317) has been suggested to be a molecular state made from D K and Dsη interactions in many studies; see, e.g., Refs. [23,24,25,26,27,28]
In Ref. [18], the authors point out that if one assumes a molecular picture for the X (5568), heavy-quark symmetry dictates that the charmed partner of X (5568) should be located around 2.24 ± 0.15 GeV
Summary
An apparently exotic mesonic state, the so-called X (5568) state, was observed by the D0 Collaboration in the Bs0π ± invariant mass spectrum [1]. MeV, respectively, and the preferred spin-parity is J P = 0+ This state, being one of the exotic X Y Z states [2], should contain at least four valence quark flavors u, d, s, and b. The unitary chiral perturbation theory (UChPT), respecting both approximate heavy-quark symmetry and chiral symmetry and their breaking pattern, has turned out to be a useful tool in understanding the X Y Z states. When extended to the bottom sector guided by heavy-quark symmetry, the covariant UChPT shows that the interactions in the Bsπ –B Kchannel are rather weak and do not support the existence of a low-lying resonance or bound state, consistent with an explicit search on the second Riemann sheet [28]
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