EPJ

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EPJ C - Particles and Fields
Particles and Fields
Eur. Phys. J. C 9, 141-158
DOI 10.1007/s100529900023

Scalar mesons and multichannel amplitudes

R. Kaminski1 - L. Lesniak1 - B. Loiseau2

1 Department of Theoretical Physics, H. Niewodniczanski Institute of Nuclear Physics, PL 31-342 Kraków, Poland
2 LPTPE Université P. et M. Curie, 4, Place Jussieu, F-75252 Paris Cedex 05, France

Received: 19 October 1998 / Revised version: 25 January 1999 / Published online: 15 April 1999

Abstract
Properties of scalar-isoscalar mesons are analyzed in a unitary model using separable interactions in three decay channels: $\pi\pi$ , $K\overline{K}$and an effective $2\pi2\pi$. We obtain different solutions by fitting various data on the $\pi\pi$ and $K\overline{K}$ phase shifts and inelasticities including the CERN-Cracow-Munich measurements of the $\pi^- p_{\uparrow} \rightarrow \pi^+ \pi^- n$reaction on a polarized target. The analytical structure of the meson-meson multichannel amplitudes is studied with special emphasis on the role played by the S-matrix zeroes. S-matrix poles, located in the complex energy plane not too far from the physical region, are interpreted as scalar resonances. We see a wide f0(500), a narrow f0(980) and a relatively narrow f0(1400). In one of our solutions a resonance at about 1700 MeV is also found. Total, elastic and inelastic channel cross sections, branching ratios and coupling constants are evaluated and compared with available data. We construct an approximation to our model and show that the Breit-Wigner approach has a limited phenomenological applicability.

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