First observation of three pseudoscalar states inJ/ψ→γρρdecay

The Jψ→γ${\pi }^{+}$ ${\pi }^{-}$ ${\pi }^{+}$ ${\pi }^{-}$ and J/ψ→γ${\mathrm{\pi }}^{+}$ ${\mathrm{\pi }}^{\mathrm{-}}$ ${\mathrm{\pi }}^0$ ${\mathrm{\pi }}^0$ decays have been studied by the DM2 experiment from 8.6×${10}^6$ J/ψ’s. Both decays exhibit a large pseudoscalar ρρ dynamics. Three $J^{\mathrm{PC}}$ ${=0\mathrm{}}^{\mathrm{-}+}$ resonant states (more than 3500 events, globally) decaying into ${\rho }^0$ ${\rho }^0$ and with less statistical significance into ${\rho }^{+}$ ${\rho }^{\mathrm{-}}$ are observed. Their branching ratios into ${\rho }^0$ ${\rho }^0$ and ${\rho }^{+}$ ${\rho }^{\mathrm{-}}$ support an $I^G$ ${=0\mathrm{}}^{+}$ assignment. These states, named η(1500), η(1800), and η(2100), are not associated with well-established resonances.