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

Abstract

Based on a sample of $(1310.6 \pm 7.0) \times 10^6~J/\psi$ events collected with the BESIII detector, we present measurements of $J/\psi$ and $\eta^\prime $ absolute branching fractions using the process $J/\psi\rightarrow\gamma\eta^\prime$. By analyzing events where the radiative photon converts into an $e^+e^−$ pair, the branching fraction for $J/\psi\rightarrow\gamma\eta^\prime$ is measured to be $(5.27\pm0.03\pm0.05)\times 10^{-3}$. The absolute branching fractions of the five dominant decay channels of the $\eta^\prime$ are then measured independently for the first time and are determined to be $\mathcal{B}(\eta^\prime \rightarrow \eta \pi^{+} \pi^{-})$ $=$ $(29.90±0.03±0.55)%$, $\mathcal{B}(\eta^\prime \rightarrow \gamma \pi^{+} \pi^{-})$ $=$ $(41.24±0.08±1.24)%$, $\mathcal{B}(\eta^\prime \rightarrow \eta \pi^{0} \pi^{0})$ $=$ $(21.36±0.10±0.92)%$, $\mathcal{B}(\eta^\prime \rightarrow \gamma \omega)$ $=$ $(2.489±0.018±0.074)%$, and $\mathcal{B}(\eta^\prime \rightarrow \gamma \gamma)$ $=$ $(2.331±0.012±0.035)%$, where the first uncertainties are statistical and the second systematic.