Precision Measurement of the Branching Fractions of $\eta$' Decays

Abstract

Based on a sample of (1310.6±7.0)×106 J/ψ events collected with the BESIII detector, we present measurements of J/ψ and $\eta^\prime $ absolute branching fractions using the process J/ψ→γη′. By analyzing events where the radiative photon converts into an e+e− pair, the branching fraction for J/ψ→γη′ is measured to be (5.27±0.03±0.05)×10−3. The absolute branching fractions of the five dominant decay channels of the η′ are then measured independently for the first time and are determined to be B(η′→ηπ+π−) = (29.90±0.03±0.55), B(η′→γπ+π−) = (41.24±0.08±1.24), B(η′→ηπ0π0) = (21.36±0.10±0.92), B(η′→γω) = (2.489±0.018±0.074), and B(η′→γγ) = (2.331±0.012±0.035), where the first uncertainties are statistical and the second systematic.