Partial wave analysis of J/psi to gamma phi phi

Using $5.8 times 10^7 J/psi$ events collected in the BESII detector, the radiative decay $J/psi to gamma phi phi to gamma K^+ K^- K^0_S K^0_L$ is studied. The $phiphi$ 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 ($eta(2225)$) 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: $Br(J/psi to gamma eta(2225))cdot Br(eta(2225)to phiphi) = (4.4 pm 0.4 pm 0.8)times 10^{-4}$.