Fully heavy asymmetric scalar tetraquarks

Abstract

The scalar tetraquarks $T_b$ and $T_c$ with asymmetric contents $bb\overline{b}\overline{c}$ and $cc\overline{c}\overline{b}$ are explored using the QCD sum rule method. These states are modeled as the diquark-antidiquarks composed of the axial-vector components. The masses and current couplings of $T_b$ and $T_c$ are calculated using the two-point sum rule approach. The predictions obtained for the masses of these four-quark mesons prove that they are unstable against the strong two-meson fall-apart decays to conventional mesons. In the case of the tetraquark $T_b$ this is the decay $T_{\mathrm{b}}\to \hat{I}{\cdot }_b{B}_c^{-}$. The processes $T_{\mathrm{c}}\to \hat{I}{\cdot }_c{B}_c^{+}$ and $J/\ddot{I}ˆB_c^{\ast +}$ are kinematically allowed decay modes of the tetraquark $T_c$. The widths of corresponding processes are evaluated by employing the QCD three-point sum rule approach which are necessary to estimate strong couplings at the tetraquark-meson-meson vertices of interest. The mass $m=(15698\pm 95)\mathrm{MeV}$ and width $\hat{I}“[T_b]=(36.0\pm 10.4)\mathrm{MeV}$ of the tetraquark $T_b$ as well as the parameters $\tilde{m}=(9680\pm 102)\mathrm{MeV}$ and $\hat{I}“[T_c]=(54.7\pm 12.6)\mathrm{MeV}$ in the case of $T_c$ provide useful information to search for and interpret new exotic states.

11 Pages and 5 Figures