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 ( $$q\bar{q}b\bar{b}$$ q q ¯ b b ¯ with $$q=$$ q = u, d and s) and double-bottom ( $$q\bar{q}bb$$ q q ¯ b b ) 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 $$X_{q\bar{q}}$$ X q q ¯ , $$Z_{b}$$ Z b , and $$Z_{bs}$$ 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 $$I^G(J^P)=1^+(1^{+})$$ I G ( J P ) = 1 + ( 1 + ) are close to $$Z_b^\pm (10610)$$ Z b ± ( 10610 ) , so one may expect these states to be non-negligible components of the experimentally observed $$Z_{b}$$ Z b states. Concerning to the double-bottom tetraquark states, the present results are in general consistent with other previous works. Two possible stable $$T_{bb}$$ T bb states with quark content $$bb\bar{n}\bar{n}$$ b b n ¯ n ¯ ( $$n=u$$ n = u or d quark) lying at energies 10558 MeV and 10650 MeV are found, and one possible stable $$bb\bar{n}\bar{s}$$ b b n ¯ s ¯ state is found, whose energy is $$\sim 10687$$ ∼ 10687 MeV.