Exploring the Structure of a Possible Light Scalar Nonet(§4. Meson Spectroscopy and Quark Model,Possible Existence of the σ-Meson and Its Implications to Hadron Physics)

Abstract

We first review the work of the Syracuse group, which uses an effective chiral Lagrangian approach, on meson-meson scattering. An illustration providing evidence for the existence of a strange scalar resonance of mass around 900 MeV is given. An attempt to fit this κ(900) together with a similarly obtained σ(560) and the well known a_0(980) and f_0(980) into a nonet pattern. suggests that the underlying structure is closer to a dual quark-dual antiquark than to a quark-antiquark. A possible mechanism to explain a next higher-in mass scalar meson nonet is also discussed. This involves mixing between qq^^- and qqq^^-q^^- states.