Partial wave analysis of J/ψ→γ(ηπ+π−)

A partial wave analysis of BES J / ψ → γ ( ηπ + π − ) data has been performed in the mass region 1.1 to 2.0 GeV. A peak is observed due to η (1440) in the ηπ + π − invariant mass distribution; J P =0 − is preferred over 1 + . Its mass is M =1385±7 MeV and it decays into both ησ and a 0 (980) π , with BR[ a 0 (980) π , a 0 → ηπ / ησ ]=0.70±0.12( stat )±0.20( syst ). Destructive interference between the two decay modes is observed. In addition, in the higher ηπ + π − mass region, there is a definite 2 −+ signal, with M =1840±15 MeV and Γ =170±40 MeV and an additional 0 −+ signal at 1760±35 MeV. We also find a possible contribution from a 1 ++ signal decaying dominantly through a 0 (980) π ; its mass and width are fitted to be M =1505±20 MeV and Γ =130 −20 +50 MeV.