Observation of the Decayψ(3684)→ψ(3095)η

Abstract

We have observed the decay $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)\mathrm{}\eta$ with a branching fraction of (4.3±0.8)%. This measurement, together with previous measurements of $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)+\mathrm{anything}$, $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)\mathrm{}{\pi }^{+}{\pi }^{-}$, and $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)\mathrm{}\gamma \gamma$, indicates that isospin is conserved in the decay $\psi \mathrm{}\left(3684\right)\mathrm{}\to \psi \mathrm{}\left(3095\right)\mathrm{}\pi \pi$ and establishes the isospin and $G$ parity of the $\psi \mathrm{}\left(3684\right)\mathrm{}$ to be $I^G=0^{-}$.