Pion production by pions in the 16O (π+,π+π-) reaction at Tπ+ = 280 MeV

The results of an experiment of pion-induced pion production on 16O at a laboratory energy of 280 MeV are reported. The four-fold-differential cross section, d4σ/dΩsub(π+)dΩsub(π-)dEsub(π+)dEsub(π-), was measured, and the missing mass, Mx, for the reaction 16O(π+,π+π-) at laboratory angles of 500, 800 and 1150 for the π-, and from 220 to 1280 for the π+ was deduced. The angular and energy distributions of the many-fold differential cross sections are compared with an A(π+,π+π-) model for the reaction. The observed cross sections are reproduced in magnitude and shape when the theoretical calculations consider a proper pion dispersion relation, ω(q), inside the nuclear medium. The total cross section, deduced by integrating the four-fold differential cross sections, is compared with the available theoretical predictions for the 16O(π+,π+π-) reaction. (orig.)