Observation of spin-1 ${\mathit{f}}_1$(1285) in the reaction γγ*→${\mathrm{\eta }}^0$${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$

We observe both the ${\mathit{J}}^{\mathit{P}\mathit{C}}$=$1^{++}$ ${\mathit{f}}_1$(1285) and the ${\mathit{J}}^{\mathit{P}\mathit{C}}$=$0^{\mathrm{-}+}$ η’(958) in tagged two-photon interactions and the η’(958) in untagged interactions. The measured $Q^2$ dependence and decay distribution support the $f_1$(1285) spin and parity assignment. The radiative width of the $f_1$(1285) is measured as (${\mathit{M}}^2$/${\mathit{Q}}^2$)${\mathrm{\Gamma }}_{\gamma \gamma \mathrm{*}}$=9.4±2.5±1.7 keV, on the assumption of a ρ-pole form factor.