Peculiarities in multichannel interaction amplitudes for meson-meson   scattering and scalar meson spectroscopy
  Interactions in coupled channels pipi, KKbar and an effective 2pi2pi in scalar-isoscalar wave have been analysed. Influence of interchannel couplings on analytical structure of multichannel interaction amplitudes has been studied. Interplay of S-matrix zeroes and poles and their relation with parameters of scalar resonances has been investigated. 
R. Kaminski, L. Lesniak and B. Loiseau