Search for the decay $\eta'\to\gamma\gamma\eta$

Abstract

Using a data sample of 1.31×109 J/ψ events collected with the BESIII detector, a search for η′→γγη via J/ψ → γη′ is performed for the first time. No significant η′ signal is observed in the γγη invariant mass spectrum, and the branching fraction of η′→γγη is determined to be less than 1.33 × 10−4 at the 90% confidence level.