Fully heavy asymmetric scalar tetraquarks

TL;DR

This paper predicts the masses and decay widths of asymmetric scalar tetraquarks with heavy quarks using QCD sum rules, indicating their instability against strong decays and providing data for experimental searches.

Contribution

It introduces a QCD sum rule approach to calculate properties of heavy asymmetric scalar tetraquarks, including their masses, couplings, and decay widths, which is a novel application for these states.

Findings

Mass of T_b: 15698 ± 95 MeV

Width of T_b: 36.0 ± 10.4 MeV

Mass of T_c: 9680 ± 102 MeV

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 $T_{\mathrm{b}}\to \eta _{b}B_{c}^{-}$. The processes $T_{\mathrm{c}}\rightarrow \eta _{c}B_{c}^{+}$ and $J/\psi B_{c}^{\ast +}$ 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 $\Gamma[T_b]=(36.0 \pm 10.4)~ \mathrm{MeV}$ of the tetraquark $T_{b}$ as well as the parameters $ \widetilde{m}=(9680 \pm 102)~\mathrm{MeV}$ and $\Gamma[T_c]=(54.7 \pm 12.6)~ \mathrm{MeV}$ in the case of $T_{c}$ provide useful information to search for and interpret new exotic states.