Radiative decays of \phi-meson and nature of light scalar resonances

Abstract

Based on gauge invariance, we show that the new threshold phenomenon is discovered in the \phi radiative decays \phi\to\gamma a0\to\gamma\pi0\eta and \phi\to\gamma f0\to\gamma\pi0\pi0. This enables to conclude that production of the lightest scalar mesons a0(980) and f0(980) in these decays is caused by the four-quark transitions, resulting in strong restrictions on the large Nc expansions of the decay amplitudes. The analysis shows that these constraints give new evidences in favor of the four-quark nature of a0(980) and f0(980) mesons.