Type: Article
Publication Date: 2021-11-18
Citations: 2
DOI: https://doi.org/10.1103/physrevd.104.092004
Based on a data sample of $(1.0087\ifmmode\pm\else\textpm\fi{}0.0044)\ifmmode\times\else\texttimes\fi{}{10}^{10}\text{ }\text{ }J/\ensuremath{\psi}$ events collected by the BESIII detector at the BEPCII accelerator, the absolute branching fraction (BF) of the decay $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\eta}$ is measured with high precision using events in which the radiative photon converts to ${e}^{+}{e}^{\ensuremath{-}}$. Using the measured absolute BF of $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\eta}$, the absolute BFs of four dominant $\ensuremath{\eta}$ decay modes are measured for the first time. The results are $\mathcal{B}(J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\eta})=(1.067\ifmmode\pm\else\textpm\fi{}0.005\ifmmode\pm\else\textpm\fi{}0.023)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, $\mathcal{B}(\ensuremath{\eta}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})=(39.86\ifmmode\pm\else\textpm\fi{}0.04\ifmmode\pm\else\textpm\fi{}0.99)%$, $\mathcal{B}(\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0})=\phantom{\rule{0ex}{0ex}}(31.96\ifmmode\pm\else\textpm\fi{}0.07\ifmmode\pm\else\textpm\fi{}0.84)%$, $\mathcal{B}(\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0})=(23.04\ifmmode\pm\else\textpm\fi{}0.03\ifmmode\pm\else\textpm\fi{}0.54)%$, and $\mathcal{B}(\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma})=(4.38\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.02\ifmmode\pm\else\textpm\fi{}0.10)%$, where the first and second uncertainties are statistical and systematic, respectively. The results are consistent with the world average values within two standard deviations.