Measurement of Branching Ratios for $η_c$ Hadronic Decays

Abstract

In a sample of 58 million $J/ψ$ events collected with the BES II detector, the process J/$ψ\toγη_c$ is observed in five decay channels: $η_c \to K^+K^-π^+π^-$, $π^+π^-π^+π^-$, $K^\pm K^0_S π^\mp$ (with $K^0_S\toπ^+π^-$), $ϕϕ$ (with $ϕ\to K^+K^-$) and $p\bar{p}$. From these signals, we determine $Br(J/ψ\toγη_c)\times Br(η_c\to K^+K^-π^+π^-)$ $=(1.5\pm0.2\pm0.2)\times10^{-4}$, $Br(J/ψ\toγη_c)\times Br(η_c\to π^+π^-π^+π^-)$ $=(1.3\pm0.2\pm0.4)\times10^{-4}$, $Br(J/ψ\toγη_c)\times Br(η_c\to K^\pm K_{S}^{0}π^\mp)$ $=(2.2\pm0.3\pm0.5)\times10^{-4}$, $Br(J/ψ\toγη_c)\times Br(η_c\to ϕϕ)$ $=(3.3\pm0.6\pm0.6)\times10^{-5}$ and $Br(J/ψ\toγη_c)\times Br(η_c\to p\bar{p})$ $=(1.9\pm0.3\pm0.3)\times10^{-5}$.