Estimating the mass of the hidden charm 1+(1+) tetraquark state via QCD sum rules

By using QCD sum rules, the mass of the hidden charm tetraquark [cu][(c) over bar(d) over bar] state with I-G(J(P)) = 1(+)(1(+)) (HCTV) is estimated, which presumably will turn out to be the newly observed charmonium-like resonance Z(c)(+) (3900). In the calculation, contributions up to dimension eight in the operator product expansion (OPE) are taken into account. We find m(1+)(c) = (3912(-153)(+306)) MeV, which is consistent, within the errors, with the experimental observation of Z(c)(+) (3900). Extending to the b-quark sector, m(1+)(b) = (10561(-163)(+395)) MeV is obtained. The calculational result strongly supports the tetraquark picture for the exotic states of Z(c)(+) (3900) and Z(b)(+) (10610).