Extraction of total cross section data for the pi -p--> pi + pi -n reaction.

Total cross section extractions are sometimes based on extrapolations of in-plane data to unobserved regions of phase space. The total cross section can then only be derived if assumptions are made about the distributions of the independent phase space variables. In the case of the reaction [pi][sup [minus]][ital p][r arrow][pi][sup +][pi][sup [minus]][ital n] an out-of-plane measurement, performed by our group, indicates that these assumptions made by some experimenters are partially not supported by the data.