Chiral Symmetry and Scalars

Abstract

The suggestion by Jaffe that if $σ$ is a light $q^{2}\bar{q}^{2}$ state $0^{++}$ then even the fundamental chiral transformation properties of the $σ$ becomes {\bf unclear}, has stimulated much interest. Adler pointed out that in fact the seminal work on chiral symmetry via PCAC consistency, is really quite consistent with the $σ$ being predominantly $q^{2}\bar{q}^{2}$. This interpretation was actually backed by subsequent work on effective Lagrangian methods for linear and non linear realizations. More recent work of Achasov suggests that intermediate four-quark states determine amplitudes involving other scalars $a_{0}(980)$ and $f_{0}(980)$ below 1 GeV, and the report by Ning Wu that study on $σ$ meson in $J/ψ\to ωπ^{+}π^{-}$ continue to support a non $q\bar{q}$ $σ$ with mass as low as 390 MeV. It is also noted that more recent re-analysis of $πK$ scattering by S. Ishida {\em et al.} together with the work of the E791 Collaboration, support the existence of the scalar $κ$ particle with comparatively light mass as well.