Light scalars as tetraquarks or two-meson states from large N_c and unitarized Chiral Perturbation Theory

By means of unitarized Chiral Perturbation Theory it is possible to obtain a remarkable description of meson-meson scattering amplitudes up to 1.2 GeV, and generate poles associated to scalar and vector resonances. Since Chiral Perturbation Theory is the QCD low energy effective theory, it is then possible to study its large N_c limit where q q̅ states are easily identified. The vectors thus generated follow closely a q q̅ behavior, whereas the light scalar poles follow the large-N-c behavior expected for a dominant tetraquark or two-meson structure