Abstract
Using a data sample of $1.31\times10^{9} ~J/\psi$ events collected with the BESIII detector, a search for $\eta'\to\gamma\gamma\eta$ via $J/\psi\to\gamma\eta'$ is performed for the first time. No significant $\eta'$ signal is observed in the $\gamma\gamma\eta$ invariant mass spectrum, and the %upper limit of the branching fraction of $\eta'\to\gamma\gamma\eta$ is determined to be less than $1.33 \times 10^{-4}$ at the 90$\%$ confidence level.
Highlights
The η0 meson provides a unique opportunity for understanding the distinct symmetry-breaking mechanisms
its decays play an important role in exploring the effective theory of quantum chromodynamics (QCD) at low energy
The dominant contributions come from the vector meson exchange processes
Summary
The η0 meson provides a unique opportunity for understanding the distinct symmetry-breaking mechanisms present in low-energy quantum chromodynamics (QCD) [1–5], and its decays play an important role in exploring the effective theory of QCD at low energy [6]. Within the frameworks of the linear σ model and the vector meson dominance (VMD) model [7,8], the branching fractions of η0 → γγπ[0] and η0 → γγη are predicted to be 3.8 × 10−3 and 2.0 × 10−4 [8], respectively. The dominant contributions come from the vector meson exchange processes, where for η0 → γγπ[0], the ω contributes 80.2% of the total VMD signal, while the ρ contributes 4.6%. By excluding the intermediate contributions from ωðρ0Þ → γπ[0], the so-called nonresonant branching fraction of η0 → γγπ[0] was determined to be ð6.16 Æ 0.64 Æ 0.67Þ × 10−4 [9], which confirmed the theoretical prediction and indicated that this decay was dominated by the VMD processes. The BESIII experiment using J=ψ radiative decays has observed a series of η0 new decay modes [11–17], and in this paper we present a search for η0 → γγη in the J=ψ radiative decay
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