Analysis of the experiment on the measurement of four-dimensional differential cross sections in the reaction pi(-)p ->pi(-)pi(+)n at p=400 MeV/c - art. no. 045203

An analysis of the experiment of the Erlangen group on the density distribu tion measurement for the reaction pi(-) p --> pi(-) pi(+)n at the Paul Sche rrer Institute accelerator is presented. Revised data were used to determin e the reaction amplitude parameters including mr scattering lengths. It is shown that the amplitude a(0)(I=2) can only be extracted with large uncerta inties from these data, while a(0)(I=0) and three other scattering lengths are obtained with rather good statistical accuracy. However, the available experimental data do not allow one to make a good choice between several so lutions which essentially increases the theoretical uncertainties of the pi pi scattering lengths obtained, It is shown that the location of detectors in this experiment was not optimal for selecting the one pion exchange (OP E) graph effects.