The Zb(10610) and Zb(10650) as axial-vector tetraquark states in the QCD sum rules

In this article, we study the axial-vector mesons Z(b)(10 610) and Z(b)(10 650) with the C gamma(mu)-C gamma(5) type and C gamma(mu)-C gamma(nu) type interpolating currents, respectively, by carrying out the operator product expansion to the vacuum condensates up to dimension 10. In calculations, we explore the energy scale dependence of the QCD spectral densities of the hidden bottom tetraquark states in detail for the first time, and suggest a formula mu =root M-X/Y/Z(2)-(2M(b))(2) with the effective mass M-b = 5.13 GeV to determine the energy scales. The numerical results favor assigning the Z(b)(10610) and 4(10 650) as the C gamma(mu)-C gamma(5) type and C gamma(mu)-C gamma(nu) type hidden bottom tetraquark states, respectively. We obtain the mass of the J(PC) = 1(++) hidden bottom tetraquark state as 'a byproduct, which can be compared to the experimental data in the futures. Furthermore, we study the strong decays Z(b)(+/-) (10 610) -> Upsilon pi(+/-), eta(b)rho(+/-) with the three-point QCD sum rules, the decay widths also support assigning the Z(b)(10 610) as the C gamma(mu)-C gamma(5) type hidden bottom tetraquark state. (C) 2014 Elsevier B.V. All rights reserved.