Abstract
The recently observed Y(4260) lies far above the decay threshold with a width less than 100 MeV. We argue that it is very difficult to accommodate Y(4260) as a conventional cc¯ radial excitation or a D-wave state. It cannot be a hadronic molecule. Its production mechanism and special decay pattern do not favor the glueball interpretation. If Y(4260) is a scalar tetraquark, it must be produced by the I=0 component of the virtual photon. Then the I=1,Iz=0 component of the virtual photon should have produced its isovector partner Y′(4260), which may be searched for in the decay channel π+π−π0J/ψ using exactly the same database from the initial state radiation process. The observation/non-observation of Y′(4260) can easily confirm/reject the tetraquark hypothesis. However, a tetraquark far above threshold can fall apart into DD¯,D*D¯ very easily. Its not-so-large width and the non-observation of DD¯ mode tend to disfavor the tetraquark hypothesis. Hence the only feasible interpretation is a hybrid charmonium if Y(4260) is NOT an experimental artifact. At present, none of the experimental information from BaBar measurement is in conflict with the hybrid charmonium picture.
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