Abstract

The coupled processes-the pi pi scattering and pi pi -> K (K) over bar in the I(G)J(PC) = 0(+)0(++) channel-are analyzed (both separately and combined) in a model-independent approach based on analyticity and unitarity and using a uniformization procedure. We show that (1) a structure of the Riemann surface of the S matrix for considered coupled processes must be allowed for calculating both amplitudes and resonance parameters, such as the mass and width; and (2) the combined analysis of coupled processes is needed as the analysis of only the pi pi channel does not give correct values of resonance parameters even if the Riemann surface structure is included.