Interpretation of $\textbackslashensuremath\textbackslashrho$ and $\textbackslashensuremath\textbackslashzeta$ Mesons

The ρ and ζ mesons are assumed to have the same quantum numbers, I=J=1. The P-wave pion-pion scattering is then studied in the hope that the two resonances, ρ and ζ, can be ascribed to the existence of one unstable vector meson B of isospin one. Besides the process 2π⇄B, a strong attractive interaction between pions in the I=J=1 state, which is caused by the exchange of B between pions and also by baryon loops, etc., is considered. The pion-pion scattering amplitude is calculated by the chain-diagram approximation and two resonances, which can be identified with the ρ and ζ mesons, are obtained. The two resonances in the kaon-pion system are discussed on the same lines.