Anomalous decay f1(1285)→ργ and related processes

We work out the low-energy expansion of the anomalous f1(1285)→ργ decay amplitude by using the Nambu–Jona-Lasinio model with U(2)×U(2) chiral symmetric four-quark interactions in the one-quark-loop approximation. The related processes f1(1285)→ωγ, a1(1260)→ωγ, and a1(1260)→ργ, are also considered. An effective meson Lagrangian responsible for f1ργ, f1ωγ, a1ργ and a1ωγ interactions is found. The predicted radiative decay widths, Γf1→ρ0γ=311 keV, Γf1→ωγ=34.3 keV, Γa1→ρ0γ=26.8 keV, Γa1→ωγ=238 keV, allow an experimental test of the hypothesis that f1(1285) and a1(1260)-mesons have a quark-antiquark nature. At present, only the f1(1285)→ργ decay has been measured. Our result is in remarkably good agreement with the recent data of CLAS Collaboration Γf1→ρ0γ=453±177 keV, but disagrees with the Particle Data Group-based estimate of Γf1→ρ0γ=1326±313 keV. The calculations presented require a minimum of theoretical input, and are shown to be consistent with the nonrenormalization theorems of QCD.