Measurement of the branching fraction of $\psip \to ωηη$

Abstract

Using a sample of (2.712 $\pm$ 0.014)$\times 10^9$ $\psip$ events collected with the BESIII detector at the BEPCII collider in 2009, 2012, and 2021, the decay $\psip \to ωηη$ is observed for the first time. The branching fraction of the $\ddot{I}ˆ(3686)\to \ddot{I}‰\hat{I}\cdot \hat{I}\cdot$ decay is measured to be (1.65 $\pm$ 0.02 $\pm$ 0.21)$\times 10^{-5}$, where the first uncertainty is statistical and the second systematic. Clear structures associated with the well-established $\ddot{I}‰(1420)$ and $f_0(1710)$ resonances are observed in the $\ddot{I}‰\hat{I}\cdot$ and $\hat{I}\cdot \hat{I}\cdot$ invariant-mass spectra, respectively.