We show how to obtain information about the states of an effective field theory in terms of the underlying fundamental theory. In particular, we analyze the spectroscopic nature of meson resonances from the meson-meson scattering amplitudes of the QCD low energy effective theory, combined with the expansion in the large number of colors. The vectors follow a $\overline{q}q$ behavior, whereas the $\sigma$, $\kappa$, and $f_0(980)$ scalars disappear for large $N_c$, in support of a $\overline{q}\overline{q}qq$-like nature. The $a_0$ shows a similar pattern, but the uncertainties are large enough to accommodate both interpretations.

• Received 25 September 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.102001