We study the exotic $bc\bar{ q}\bar{ q}$, $bc\bar{ s}\bar{ s}$ and $qc\bar{ q}\bar{ b}$, $sc\bar{ s}\bar{ b}$ systems by constructing the corresponding tetraquark currents with $J^P=0^+$ and $1^+$. After investigating the two-point correlation functions and the spectral densities, we perform QCD sum rule analysis and extract the masses of these open-flavor tetraquark states. Our results indicate that the masses of both the scalar and axial vector tetraquark states are about $7.1-7.2$ GeV for the $bc\bar{ q}\bar{ q}$ system and $7.2-7.3$ GeV for the $bc\bar{ s}\bar{ s}$ system. For the $qc\bar{ q}\bar{ b}$ tetraquark states with $J^P=0^+$ and $1^+$, their masses are extracted to be around $7.1$ GeV. The masses for the scalar and axial vector $sc\bar{ s}\bar{ b}$ states are $7.1$ GeV and $6.9-7.1$ GeV, respectively. The tetraquark states $qc\bar{ q}\bar{ b}$ and $sc\bar{ s}\bar{ b}$ lie below the thresholds of $D^{ (\ast)}B^{ (\ast)}$ and $D_s^{ (\ast)}B_s^{ (\ast)}$ respectively, but they can decay into $B_c$ plus a light meson. However, the tetraquark states $bc\bar{ q}\bar{ q}$ and $bc\bar{ s}\bar{ s}$ lie below the $D^{ (\ast)}\bar B^{ (\ast)}$ and $D_s^{ (\ast)}\bar B_s^{ (\ast)}$ thresholds, suggesting dominantly weak decay mechanisms.
Categories: hep-ph hep-ex