Measurement of Prominent η-Decay Branching Fractions

The decay ψ(2S)→ηJ/ψ is used to measure, for the first time, all prominent η-meson branching fractions with the same experiment in the same dataset, thereby providing a consistent treatment of systematics across branching fractions. We present results for η decays to γγ, π⁺π^-π⁰, 3π⁰, π⁺π^-γ and e⁺e^-γ, accounting for 99.9% of all η decays. The precision of several of the branching fractions and their ratios is improved. Two channels, π⁺π^-γ and e⁺e^-γ, show results that differ at the level of three standard deviations from those previously determined.