Suppressed decay into open charm for the Y(4260) being an hybrid

We investigate the Y(4260) resonance recently discovered by the BaBar Collaboration. We propose the observation of its decay into J/psi psi psi and its non-observation into open charm as a consequence of it being a charmonium hybrid state with a magnetic constituent gluon. We prove a selection rule forbidding its decay into two S-wave charmed mesons in any potential model. We suggest a generalisation of the selection rule based only on the heavy quark nature of the charm. (c) 2005 Elsevier B.V. All rights reserved.