Y(4260) as a mixed charmonium-tetraquark state
Using the QCD sum rule approach we study the Y(4260) state assuming that it can be described by a mixed charmonium-tetraquark current with $J^PC=1^--$ quantum numbers. For the mixing angle around $θ ≈ (53.0± 0.5)^0$, we obtain a value for the mass which is in good agreement with the experimental mass of the Y(4260). However, for the decay width we find the value $\Ga_Y ≈ (1.0± 0.2)$ MeV which is not compatible with the experimental value $\Ga ≈ (88± 23)$ MeV. Therefore, we conclude that, although we can explain the mass of the Y(4260), this state cannot be described as a mixed charmonium-tetraquark state since, with this assumption, we can not explain its decay width.