Partial wave analysis of J/ψ\to γϕϕ

Using $5.8 \times 10^7 J/ψ$ events collected in the BESII detector, the radiative decay $J/ψ\to γϕϕ\to γK^+ K^- K^0_S K^0_L$ is studied. The $ϕϕ$ invariant mass distribution exhibits a near-threshold enhancement that peaks around 2.24 GeV/$c^{2}$. A partial wave analysis shows that the structure is dominated by a $0^{-+}$ state ($η(2225)$) with a mass of $2.24^{+0.03}_{-0.02}{}^{+0.03}_{-0.02}$ GeV/$c^{2}$ and a width of $0.19 \pm 0.03^{+0.06}_{-0.04}$ GeV/$c^{2}$. The product branching fraction is: $Br(J/ψ\to γη(2225))\cdot Br(η(2225)\to ϕϕ) = (4.4 \pm 0.4 \pm 0.8)\times 10^{-4}$.

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