Lightest scalar in the SU_L(2)*SU_R(2) linear σmodel

Abstract

We consider the lightest scalar meson in the frame of the $S{U}_L(2)\times S{U}_R(2)$ linear $\sigma$ model, keeping in mind that this model could be the low energy realization of the two-flavour QCD. We show that the $\sigma$ field is described by its four-quark component at least in the $\sigma$ resonance energy (virtuality) region and the $\sigma \to \gamma \gamma$ decay is the four quark transition. We emphasize that residues of the $\sigma$ pole in the $\pi \pi \to \pi \pi$ and $\gamma \gamma \to \pi \pi$ amplitudes do not give an idea about the $\sigma$ meson nature, and the progress in studying the $\sigma$ meson production mechanisms in different processes could essentially further us in understanding its nature.

10 pages, 3 figures, English improved, PACS numbers changed, two Refs. added, E-mail addresses removed and Ref. [1] shortened for the overrun of the article length allowable in Phys. Rev. Lett

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• Theory of Scalars