How can X±(5568) escape detection?

Abstract

Multi-quark states were predicted by Gell-Mann when the quark model was first formulated. Recently, numerous exotic states that are considered to be multi-quark states have been experimentally confirmed (four-quark mesons and five-quark baryons). Theoretical research indicates that the four-quark state might comprise molecular and/or tetraquark structures. We consider that the meson containing four different flavors sub¯d¯ should exist and decay via the X(5568)→Bsπ channel. However, except for the D0 collaboration, all other experimental collaborations have reported negative observations for X(5568) in this golden portal. This contradiction has stimulated the interest of both theorists and experimentalists. To address this discrepancy, we propose that the assumed X(5568) is a mixture of a molecular state and tetraquark, which contributes destructively to X(5568)→Bsπ. The cancellation may be accidental and it should be incomplete. In this scenario, there should be two physical states with the same flavor ingredients, with spectra of 5344±307 and 6318±315. X(5568) lies in the error range of the first state. We predict the width of the second state (designated as S2) as Γ(XS2→Bsπ)=224±97 MeV. We strongly suggest searching for it in future experiments.