Heavy quarkonium π+π− transitions and a possible bb¯qq¯ state

π+π− transitions of heavy quarkonia, especially the ϒ(3S)→ϒ(1S)π+π− decay process, are revisited. In the framework of the Chiral Unitary Theory (ChUT), the S wave ππ final state interaction (FSI) is included. It is found that when an additional intermediate state with JP=1+ and I=1 is introduced, not only the ππ invariant mass spectrum and the cosθπ∗ distribution in the ϒ(3S)→ϒ(1S)π+π− process can simultaneously be well explained, but also a consistent description for other bottomonia π+π− transitions can be obtained. As a consequence, the mass and the width of the intermediate state are predicted. From the quark content analysis, this state should be a bb¯qq¯ state.