Measurement of branching fractions for $\psi(3686)\rightarrow\gamma\eta',\gamma\eta$ and $\gamma\pi^{0}$

TL;DR

This study measures the branching fractions of $ ext{psi}(3686)$ decays into $ ext{gamma} ext{eta}$, $ ext{gamma} ext{pi}^0$, and $ ext{gamma} ext{eta'}$ using a large data sample, providing more precise results and confirming these rare decay modes.

Contribution

First measurement of $ ext{psi}(3686)$ radiative decays into $ ext{eta}$ and $ ext{pi}^0$ with improved precision, expanding understanding of charmonium decay processes.

Findings

Branching fraction for $ ext{psi}(3686) ightarrow ext{gamma} ext{eta}$ is $(0.85 extpm0.18 extpm0.05) imes10^{-6}$.

Branching fraction for $ ext{psi}(3686) ightarrow ext{gamma} ext{pi}^0$ is $(0.95 extpm0.16 extpm0.05) imes10^{-6}$.

Branching fraction for $ ext{psi}(3686) ightarrow ext{gamma} ext{eta'}$ is $(125.1 extpm2.2 extpm6.2) imes10^{-6}$.

Abstract

Using a data sample of $448\times10^{6}$ $\psi(3686)$ events collected with the BESIII detector operating at the BEPCII storage ring, the decays $\psi(3686)\rightarrow\gamma\eta$ and $\psi(3686)\rightarrow\gamma\pi^{0}$ are observed with a statistical significance of $7.3\sigma$ and $ 6.7\sigma$, respectively. The branching fractions are measured to be $\mathcal{B}(\psi(3686)\rightarrow\gamma\eta)=(0.85\pm0.18\pm0.05)\times10^{-6}$ and $\mathcal{B}(\psi(3686)\rightarrow\gamma\pi^{0})=(0.95\pm0.16\pm0.05)\times10^{-6}$. In addition, we measure the branching fraction of $\psi(3686)\rightarrow\gamma\eta'$ to be $\mathcal{B}(\psi(3686)\rightarrow\gamma\eta')=(125.1\pm2.2\pm6.2)\times 10^{-6}$, with improved precision compared to previous results.