Peculiarities in multichannel interaction amplitudes for meson-meson scattering and scalar meson spectroscopy

Interactions in coupled channels ππ, KK̄ and an effective 2π2π 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. PACS numbers: 11.80.Gw, 13.60.Le, 13.75.Lb, 14.40.Cs Structure and dynamics of scalar mesons is still not clear and is a subject of many theoretical and experimental efforts [1]. Their multichannel decays and possible interference with glueball states below 2 GeV make results of analyses very model-dependent. In our model we use separable potentials [2, 3] for three coupled channels: ππ , KK and σσ (an effective 2π2π) in S-wave with isospin 0. We also do not assume the existence of any scalar mesons before fitting experimental data. As experimental data for the ππ interactions we use ”down-flat” and ”up-flat” solutions of [4] in the effective two-pion mass mππ range from 600 MeV to 1600 MeV. Below 600 MeV we use the ππ data described in [2] and the KK channel data of [5].