Study of η (1475 ) and X (1835 ) in radiative J /ψ decays to γ ϕ

The decay J /ψ →γ γ ϕ is studied using a sample of 1.31 ×10⁹ J /ψ events collected with the BESIII detector. Two structures around 1475 MeV /c² and 1835 MeV /c² are observed in the γ ϕ invariant mass spectrum for the first time. With a fit on the γ ϕ invariant mass, which takes into account the interference between the two structures, and a simple analysis of the angular distribution, the structure around 1475 MeV /c² is found to favor an assignment as the η (1475 ) and the mass and width for the structure around 1835 MeV /c² are consistent with the X (1835 ). The statistical significances of the two structures are 13.5 σ and 6.3 σ , respectively. The results indicate that both η (1475 ) and X (1835 ) contain a sizeable s s ¯ component.