Recent BESIII data indicate a significant rate of the process e +e- →hc π+ π- at the Y(4260) and Y(4360) resonances, implying a substantial breaking of the heavy quark spin symmetry. We consider these resonances within the picture of hadrocharmonium, i.e. of (relatively) compact charmonium embedded in a light-quark mesonic excitation. We suggest that the resonances Y(4260) and Y(4360) are a mixture, with mixing close to maximal, of two states of hadrochamonium, one containing a spin-triplet cc pair and the other containing a spin-singlet heavy quark pair. We argue that this model is in a reasonable agreement with the available data and produces distinctive and verifiable predictions for the energy dependence of the production rate in e +e- annihilation of the final states J/ψππ, ψ'ππ and hc ππ, including the pattern of interference between the two resonances.
Bibliographical noteFunding Information:
This work is supported, in part, by the DOE grant DE-FG02-94ER40823.
- heavy quark spin symmetry