Fully open-flavor tetraquark states

We have studied the masses for fully open-flavor tetraquark states $$bc\bar{q}\bar{s}$$ and $$sc\bar{q}\bar{b}$$ ($$q=u, d$$) with quantum numbers $$J^{P}=0^{+},1^{+}$$. We systematically construct all diquark–antiquark interpolating currents and calculate the two-point correlation functions and spectral densities in the framework of QCD sum rule method. Our calculations show that the masses are about $$7.1-7.2$$ GeV for the $$bc\bar{q}\bar{s}$$ tetraquark states and $$7.0-7.1$$ GeV for the $$sc\bar{q}\bar{b}$$ tetraquarks. The masses of $$bc\bar{q}\bar{s}$$ tetraquarks are below the thresholds of $$\bar{B}_{s}D$$ and $$\bar{B}_{s}^{*}D$$ final states for the scalar and axial-vector channels respectively. The $$sc\bar{q}\bar{b}$$ tetraquark states with $$J^{P}=1^{+}$$ lie below the $$B_{c}^{+}K^{*}$$ and $$B_{s}^{*}D$$ thresholds. Such low masses for these possible tetraquark states indicate that they can only decay via weak interaction and thus are very narrow and stable