We report the observation and study of $J/psi
ightarrowphietaeta’$ decay
using $1.3 imes{10^9}$ $J/psi$ events collected with the BESIII detector. Its
branching fraction including all the possible intermediate states is measured
to be $(2.32pm0.06pm0.16) imes{10^{-4}}$. A structure denoted as $X$ is
observed in the $phieta’$ mass spectrum in $2.0-2.1$ GeV/$c^2$ region. A
simultaneous fit to $phieta’$ mass spectra with two decay modes of $eta’$
meson ($gammapi^+pi^-$ and $etapi^+pi^-$) is performed. Assuming the
$J^P$ value of the structure as $1^-$, the significance of the structure is
evaluated to be 5.3$sigma$; the mass and width are determined to be $(2002.1
pm 27.5 pm 15.0)$ MeV/$c^2$ and $(129 pm 17 pm 7)$ MeV, respectively; the
product branching fraction is measured to be
$mathcal{B}(J/psi
ightarroweta{}X) imes{}mathcal{B}(X
ightarrowphieta’)=(9.8
pm 1.2 pm 1.5) imes10^{-5}$. Assuming the $J^P$ value of the structure as
$1^+$, the significance of the structure is evaluated to be 4.9$sigma$; the
mass and width are determined to be $(2062.8 pm 13.1 pm 4.2)$ MeV/$c^2$ and
$(177 pm 36 pm 20)$ MeV, respectively; the product branching fraction is
measured to be
$mathcal{B}(J/psi
ightarroweta{}X) imes{}mathcal{B}(X
ightarrowphieta’)=(9.6
pm 1.4 pm 1.6) imes10^{-5}$. The angular distribution is studied and the two
assumptions could hardly be distinguished due to the limited statistics. In all
measurements the first uncertainties are statistical and the second systematic.
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