Decoding the X(5568) as a Fully Open-Flavor su(b)over-bar(d)over-bar Tetraquark State

We investigate the recent evidence for a charged X(5568) meson as an exotic open-flavor tetraquark state su (b) over bar(d) over bar with J(P) = 0(+)/1(+) in the framework of QCD sum rules. We use the color antisymmetric [(3) over bar (c)](su) circle times [3(c)]((b) over bar(d) over bar) tetraquark currents in both scalar and axial-vector channels to perform evaluations and numerical analyses. Our results imply that the X(5568) can be interpreted as both the scalar su (b) over bar(d) over bar tetraquark state and the axial-vector one, which are in good agreement with the experimental measurement. We also discuss the possible decay patterns of the X(5568) and suggest to search for its neutral partner in the radiative decay into B-s(0)gamma and B-s*gamma, which can be used to determine its spin-parity quantum numbers. Moreover, we predict its charmed partner state around 2.55 GeV with the quark content su (c) over bar(d) over bar and J(P) = 0(+)/1(+).