Partial wave analysis of J/ψ→γϕϕ

Using 5.8×107J/ψ events collected in the BESII detector, the radiative decay J/ψ→γϕϕ→γK+K−KS0KL0 is studied. The ϕϕ invariant mass distribution exhibits a near-threshold enhancement that peaks around 2.24 GeV/c2. A partial wave analysis shows that the structure is dominated by a 0−+ state (η(2225)) with a mass of 2.24−0.02+0.03−0.02+0.03 GeV/c2 and a width of 0.19±0.03−0.04+0.06 GeV/c2. The product branching fraction is: Br(J/ψ→γη(2225))⋅Br(η(2225)→ϕϕ)=(4.4±0.4±0.8)×10−4.