ON PHENOMENOLOGICAL SIGMA-MODELS

In the framework of the linear sigma model the question of the phenomenological description of broad scalar resonances compatible with chiral symmetry and unitarity is discussed. It is shown that naive inclusion of decay widths in the propagators of scalar mesons is not an adequate approximation for the physical amplitudes. In this connection a critical discussion of work by Shabalin (Refs. 8-10) is given. In particular, possible modifications of some results (Refs. 9 and 10) for K+ --> pi+pi-e+nu and K(S) --> pipi) decays connected with the requirements of the unitarity condition are considered.