PION-PRODUCTION IN THE REACTION PI(-)P-UP-ARROW-]PI(-)PI(+)ETA ON A POLARIZED PROTON TARGET AT 1.78 GEV C/

Dipion production by a beam of 1.78-GeV/c negative pions on polarized- proton and liquid-hydrogen targets has been studied experimentally. Th e experimental searches covering the region of low momentum transfers have been performed for dipion-mass values close to the rho-meson mass . The complete set of the spin-density-matrix elements has been found, and model-independent and model-dependent amplitude analyses of the r eaction have been carried out. The experiment makes it possible to rem ove the high-energy ambiguity in the solution obtained from amplitude analyses. The data from this experiment support the existence of sigma (750)00(++) with mass M-sigma-744 +/- 5 h MeV and width Gamma(sigma) = 77 +/- 22 MeV and make it possible to estimate the intercept of the a (1)-meson trajectory. The experiment has been performed at the acceler ator installed at ITEP (Moscow).