LOW-ENERGY PION-PRODUCTION IN HIGH-ENERGY NUCLEUS-NUCLEUS COLLISIONS

Doubly differential cross sections for production of pions with 400-MeV/N Ne20 on C, NaF, Cu, and Pb have been measured for a range of 20 MeV<TπLAB<100 MeV and 30°<θπLAB<150°. The results are compared with previous data with 800-MeV/N Ne20. The broad maximum at θπc.m.=90° in the center-of-mass angular distribution of low-energy pions observed at 800 MeV/N is not seen at the present energy. Neither was such a maximum at the central-rapidity region observed in (p+ nucleus) reactions at Ep=730 MeV. The 90° maximum seems to be a phenomenon specific to nucleus-nucleus collisions around 1 GeV/N, where the multiplicity of Δ formation is high and multiple Δ interaction could influence the pion production. The distribution at higher bombarding energies has yet to be studied. NUCLEAR REACTIONS C, NaF, Cu, Pb(Ne20,π+)X, EA=400 MeV/nucleon; measured σ(Eπ,θπ), Eπ=20-100 MeV, θπ=30°-150°. © 1979 The American Physical Society.