Known decays of eta

(Only the first generation of decays, no cascades)

Final state Branching
$\eta^{}_{}$ $\to$ $\gamma^{}_{}$ $\gamma^{}_{}$ 3.9e-1
$\eta^{}_{}$ $\to$ $\pi^{0}_{}$ $\pi^{0}_{}$ $\pi^{0}_{}$ 3.2e-1
$\eta^{}_{}$ $\to$ $\pi^{+}_{}$ $\pi^{-}_{}$ $\pi^{0}_{}$ 2.2e-1
$\eta^{}_{}$ $\to$ $\pi^{+}_{}$ $\pi^{-}_{}$ $\gamma^{}_{}$ 4.6e-2
$\eta^{}_{}$ $\to$ $e^{+}_{}$ $e^{-}_{}$ $\gamma^{}_{}$ 7.0e-3
$\eta^{}_{}$ $\to$ $\mu^{+}_{}$ $\mu^{-}_{}$ $\gamma^{}_{}$ 3.1e-4
$\eta^{}_{}$ $\to$ $\pi^{0}_{}$ $\gamma^{}_{}$ $\gamma^{}_{}$ 2.7e-4
$\eta^{}_{}$ $\to$ $\pi^{+}_{}$ $\pi^{-}_{}$ $e^{+}_{}$ $e^{-}_{}$ 2.1e-4
$\eta^{}_{}$ $\to$ $\mu^{+}_{}$ $\mu^{-}_{}$ 5.8e-6