QCD sum rules study of the JPC=1−− charmonium Y mesons

We use QCD sum rules to test the nature of the recently observed mesons Y(4260), Y(4350) and Y(4660), assumed to be exotic four-quark or states with JPC=1−−. We work at leading order in αs, consider the contributions of higher dimension condensates and keep terms which are linear in the strange quark mass ms. We find for the state a mass mY=(4.65±0.10)GeV which is compatible with the experimental candidate Y(4660), while for the state we find a mass mY=(4.49±0.11)GeV, which is still consistent with the mass of the experimental candidate Y(4350). With the tetraquark structure we are working we cannot explain the Y(4260) as a tetraquark state. We also consider molecular and states. For the molecular state we get which is consistent, considering the errors, with the mass of the meson Y(4350) and for the molecular state we get in excellent agreement with the mass of the meson Y(4260).