Exploring the structure of a possible light scalar nonet

TL;DR

This paper reviews meson-meson scattering studies suggesting a light scalar nonet with a structure possibly closer to a dual quark-dual antiquark configuration, involving mixing mechanisms for higher-mass scalars.

Contribution

It proposes a nonet pattern for light scalar mesons based on effective chiral Lagrangian analysis and discusses mixing mechanisms for higher scalar states.

Findings

Evidence for a strange scalar resonance around 900 MeV.

Support for a nonet pattern closer to dual quark-dual antiquark structure.

Discussion of mixing between quark-antiquark and tetraquark states.

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 $\kappa (900)$ together with a similarly obtained $\sigma (560)$ 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 $q{\bar q}$ and $qq{\bar q} {\bar q}$ states.