Partial-wave analysis of J / ψ → γ γ ϕ

Using a sample of ∼ 10 10     J / ψ events collected by the BESIII detector at the BEPCII collider, a partial-wave analysis of the decay γ γ ϕ is performed to investigate the intermediate resonances in J / ψ → γ R , R → γ ϕ . Resonances including f 1 ( 1285 ) , η ( 1405 ) , f 1 ( 1420 ) , f 1 ( 1510 ) , f 2 ( 1525 ) , X ( 1835 ) , f 2 ( 1950 ) , f 2 ( 2010 ) , f 0 ( 2200 ) , and η c have been detected with statistical significance greater than 5 σ . The product branching fractions B ( J / ψ → γ R , R → γ ϕ ) are reported, and the resonance parameters of η ( 1405 ) and X ( 1835 ) have been precisely determined. It seems likely that η ( 1405 ) and X ( 1835 ) act as the first—and second—excited states of η ′ , respectively. The observation of η c → γ ϕ holds great significance for the in depth study of charmonium properties. No evidence of η ( 1295 ) , η 1 ( 1855 ) or X(2370) is found. The measured upper limits of relevant branching fraction products do not conflict with theoretical expectations for X(2370) as a pseudoscalar glueball and η 1 ( 1855 ) as a hybrid state.