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We report the observation and study of the decay$J/\psi\rightarrow\phi\eta\eta'$ using $1.3\times{10^9}$ $J/\psi$ eventscollected with the BESIII detector. Its branching fraction, including allpossible intermediate states, is measured to be$(2.32\pm0.06\pm0.16)\times{10^{-4}}$. We also report evidence for a structure,denoted as $X$, in the $\phi\eta'$ mass spectrum in the $2.0-2.1$ GeV/$c^2$region. Using two decay modes of the $\eta'$ meson ($\gamma\pi^+\pi^-$ and$\eta\pi^+\pi^-$), a simultaneous fit to the $\phi\eta'$ mass spectra isperformed. Assuming the quantum numbers of the $X$ to be $J^P = 1^-$, itssignificance is found to be 4.4$\sigma$, with a mass and width of $(2002.1 \pm27.5 \pm 21.4)$ MeV/$c^2$ and $(129 \pm 17 \pm 9)$ MeV, respectively, and aproduct branching fraction$\mathcal{B}(J/\psi\rightarrow\eta{}X)\times{}\mathcal{B}(X\rightarrow\phi\eta')=(9.8\pm 1.2 \pm 1.7)\times10^{-5}$. Alternatively, assuming $J^P = 1^+$, thesignificance is 3.8$\sigma$, with a mass and width of $(2062.8 \pm 13.1 \pm7.2)$ MeV/$c^2$ and $(177 \pm 36 \pm 35)$ MeV, respectively, and a productbranching fraction$\mathcal{B}(J/\psi\rightarrow\eta{}X)\times{}\mathcal{B}(X\rightarrow\phi\eta')=(9.6\pm 1.4 \pm 2.0)\times10^{-5}$. The angular distribution of$J/\psi\rightarrow\eta{}X$ is studied and the two $J^P$ assumptions of the $X$cannot be clearly distinguished due to the limited statistics. In allmeasurements the first uncertainties are statistical and the second systematic.

Observation and study of the decay $J/\psi\rightarrow\phi\eta\eta'$