Different nature of rho and a1

Abstract

Within the very same framework using lowest-order chiral interactions and optionally s-channel resonances it is shown that the ρ meson can be understood as a preformed (quark-antiquark) state -with only a small admixture of a π-π state -whereas the a 1 meson can be understood as a ρ-π state without the need for a preformed state.