Theoretical study on low-lying hidden-bottom and double-bottom tetraquark states

Abstract

We perform a theoretical study on the spectrum of the low-lying hidden-bottom (\(q\bar{q}b\bar{b}\) with \(q=\) u, d and s) and double-bottom (\(q\bar{q}bb\)) tetraquark states within a nonrelativistic quark model, in which the instanton-induced interaction is taken as the residual spin-dependent hyperfine interaction between quarks. All the model parameters are fixed by fitting the spectrum of the ground hadron states. The numerical results indicate that masses of several \(X_{q\bar{q}}\), \(Z_{b}\), and \(Z_{bs}\) tetraquark states are below and near thresholds of corresponding meson-meson channels, thus these states may form components of exotic meson states with reasonable probabilities. Especially, in present model, masses of several obtained states with quantum number \(I^G(J^P)=1^+(1^{+})\) are close to \(Z_b^\pm (10610)\), so one may expect these states to be non-negligible components of the experimentally observed \(Z_{b}\) states. Concerning to the double-bottom tetraquark states, the present results are in general consistent with other previous works. Two possible stable \(T_{bb}\) states with quark content \(bb\bar{n}\bar{n}\) (\(n=u\) or d quark) lying at energies 10558 MeV and 10650 MeV are found, and one possible stable \(bb\bar{n}\bar{s}\) state is found, whose energy is \(\sim 10687\) MeV.