Axial-vector molecules $\Upsilon B_{c}^{-}$ and $\eta_{b}B_{c}^{\ast-} $

Abstract

Axial-vector hadronic molecules $\mathcal{M}_{\mathrm{AV}}=\Upsilon B_{c}^{-} $ and $\widetilde{\mathcal{M}}_{\mathrm{AV}}=\eta_{b}B_{c}^{\ast -} $ with the quark content $bb \overline{b}\overline{c}$ are studied using QCD sum rule method. The spectroscopic parameters of these molecules are computed in the context of the two-point sum rule method. Predictions for their masses are identical to each other and confirm that they are structures unstable against dissociations to ordinary heavy mesons. We evaluate the width of the state $\mathcal{M}_{\mathrm{AV}}$ and assume that it is equal to that of $\widetilde{\mathcal{M}}_{\mathrm{AV}} $. To this end, we explore its dominant decay channels $\mathcal{M}_{\mathrm{AV}} \to \Upsilon B_{c}^{-} $ and $\mathcal{M}_{\mathrm{AV}} \to \eta_{b}B_{c}^{\ast -}$. There also are subleading modes of $\mathcal{M}_{\mathrm{AV}}$ generated due to annihilation of $\overline{b}b$ quarks. We consider decays of the molecule $\mathcal{M}_{\mathrm{AV}}$ to pairs of the mesons $B^{\ast -} \overline{D}^{0}$, $\overline{B}^{\ast 0} D^{-}$, $B^{-} \overline{D} ^{\ast 0}$, $\overline{B}^{0} D^{\ast -}$, $\overline{B}_{s}^{\ast 0} D_{s}^{-}$, and $\overline{B}_{s}^{0} D_{s}^{\ast -}$. To find strong couplings at the $\mathcal{M}_{\mathrm{AV}}$-meson-meson vertices which determine the partial widths of these processes, we apply QCD three-point sum rule approach. The mass $m=(15800 \pm 90)~\mathrm{MeV}$ and width $ \Gamma [\mathcal{M}_{\mathrm{AV}}]=(114 \pm 17)~ \mathrm{MeV}$ of the molecule $\mathcal{M}_{\mathrm{AV}}$ are useful for experimental studies of fully heavy molecular structures at ongoing and planning experiments.