Observation of a pseudoscalar state in J/ψ→γφφ near φφ threshold

We present a study of the radiative decay J/ψ→γφφ in the γ${\mathit{K}}^{+}$ ${\mathit{K}}^{\mathrm{-}}$ ${\mathit{K}}^{+}$ ${\mathit{K}}^{\mathrm{-}}$ and γ${\mathit{K}}^{+}$ ${\mathit{K}}^{\mathrm{-}}$ ${\mathit{K}}_{\mathit{S}}^0$ ${\mathit{K}}_{\mathit{L}}^0$ final states. A pseudoscalar state is observed in the φφ invariant-mass spectrum at 2.22 GeV/${\mathit{c}}^2$ with a width of 150 MeV/${\mathit{c}}^2$. The product branching ratios are B(J/ψ→γX)B(X→φφ)=(3.3±0.8±0.5)×${10}^{\mathrm{-}4}$ for the γ${\mathit{K}}^{+}$ ${\mathit{K}}^{\mathrm{-}}$ ${\mathit{K}}^{+}$ ${\mathit{K}}^{\mathrm{-}}$ mode and B(J/ψ→γX)B(X→φφ)=(2.7±0.6 ±0.6)×${10}^{\mathrm{-}4}$ for the γ${\mathit{K}}^{+}$ ${\mathit{K}}^{\mathrm{-}}$ ${\mathit{K}}_{\mathit{S}}^0$ ${\mathit{K}}_{\mathit{L}}^0$ mode. No evidence for $2^{++}$ states below 2.4 GeV/${\mathit{c}}^2$ is found in this radiative J/ψ decay mode.