The origin of light $0^{+}$ scalar resonances

Abstract

We demonstrate how most of the light $J^{P}=0^{+}$ spectrum below $2.0\,\mathrm{GeV}$ and their decays can be consistently described by the unitarized quark model incorporating the chiral constraints of Adler zeros and taking SU(3) breaking effects into account. These resonances appear as poles in the complex $s$ plane in a unified picture as $q\bar{q}$ states strongly dressed by hadron loops. Through the large $N_c$ analysis, these resonances are found to naturally separate into two kinds: $\sigma, \kappa, f_0(980), a_0(980)$ are dynamically generated and run away from the real axis as $N_c$ increases, while the others move towards the $q\bar q $ seeds. In this picture, the line shape of $a_0(980)$ is produced by a broad pole below the $K\bar{K}$ threshold, and exhibits characteristics similar to the $\sigma$ and $\kappa$.