Anomalous decay f_1(1285) → π~+ π~- γ in the Nambu-Jona-Lasinio model

摘要

Using the Nambu-Jona-Lasinio model with the U(2) × U(2) chiral symmetric effective four-quark interactions, we derive the amplitude of the radiative decay f_1 (1285) → π~+π~-γ, find the decay width Γ(f_1 → π~+π~-γ) = 346 keV and obtain the spectral dipion effective mass distribution. It is shown that in contrast to the majority of theoretical estimates (which consider the a_1 (1260) meson exchange as the dominant one), the most relevant contribution to this process is the ρ~0-resonance exchange related with the triangle f_1ρ~0γ anomaly. The spectral function is obtained to be confronted with the future empirical data.