Lightest scalars as chiral partners of the Nambu--Goldstone bosons

Abstract

We review the spectrum of lightest scalar resonances recently determined using dispersion techniques. The conceptual difference between the pole mass and the bare mass (or the line--shape mass) is stressed. The nature of the lightest scalars are discussed and we argue, without relying on any model details, that the $\sigma (500)$, $\kappa (700)$, $a_0(980)$ and $f_0(980)$ may be understood as chiral partners of the Nambu--Goldstone bosons in the linear realization of chiral symmetry. But there remains some difficulties in understanding the role of $f_0(980)$ in this picture.

Invited talk given by Zheng at QCD06, Montpellier, France, July 3--7, 2006

References in corpus (1)

• An improved study of the kappa resonance and the non-exotic $s$ wave $\pi K$ scatterings up to $\sqrt{s}=2.1$GeV of LASS data

Cited by in corpus (3)

• Glueball nature of the sigma/f_0(600) from pi-pi and gamma-gamma scatterings
• Gluonium nature of the sigma/f_0(600) from its coupling to KK
• Low Lying Scalar Resonances and Chiral Symmetry