Lightest scalar in the SU(L)2 x SU(R)2 linear sigma model.
We consider the lightest scalar meson in the frame of the SU(L)2 x SU(R)2 linear sigma model, keeping in mind that this model could be the low energy realization of two-flavor 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-->gammagamma decay is the four-quark transition. We emphasize that residues of the sigma pole in the pipi-->pipi and gammagamma-->pipi 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.
Achasov
N N
NN
Laboratory of Theoretical Physics, Sobolev Institute for Mathematics, Novosibirsk, 630090, Russia.
Shestakov
G N
GN