We show on gauge invariance grounds that the fine threshold phenomenon is discovered in the radiative decays φ → γa 0 → γπ 0 η and φ → γf 0 → γπ 0 π 0. This enables to conclude that production of the lightest scalar mesons a 0 (980) and f 0 (980) in these decays is caused by the four-quark transitions, resulting in strong restrictions on the large N C expansions of the decay amplitudes. The ana...

The formulae needed to parametrise σ, κ, a0(980) and f0(980) are reviewed. For σ and κ, the Adler zero due to Chiral Symmetry Breaking plays a crucial role. The f0(980) and a0(980) are locked to the KK threshold by a cusp mechanism which leads to a sharp peak in attraction at the threshold. This mechanism may play a wider role. A novel suggestion is that the confinement potential involves a coo...

Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan Graduate School of Engineering, Department of Materials Science, Tohoku University, Sendai 980-8579, Japan Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan Institute of Multidisciplinary Research fo...

Based on the main assumption that the a0(980) and D ∗ sJ (2317) belong to the 1 3P0 qq̄ multiplet, in the framework of Regge phenomenology and meson-meson mixing, it is suggested that the a0(980), K ∗ 0 (1052), f0(1099) and f0(530) constitute the ground scalar meson nonet, and that the f0(1099) is composed mostly of ss̄ while the f0(530) is mainly uū+dd̄. It is supposed that these states would lik...

We study how the scalar f0(980) and a0(980) states are produced in the two-photon collisions and radiative decays of the φ meson through unitarized Born amplitudes with the charged pion and kaon loops followed by S-wave meson-meson scattering amplitudes. We found in a previous paper that f0(980) is generated as the bound state resonance, but a0(980) as the cusp, and find here that the nature of...