Doubly differential cross sections for production of positive pions ($20 \mathrm{MeV}\le T_{\pi }^{\mathrm{Lab}}\le 100 \mathrm{MeV}$) in bombardment of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ on NaF, Cu and Pb targets at 800 MeV/N have been measured with a range telescope. The results showed that the angular distribution of low-energy pions in the nucleon-nucleon center of mass ($T_{\pi }^{\mathrm{c}.\mathrm{m}.\mathrm{}}\le 50$ MeV) was isotropic, even 90° peaking at ∼ 15 MeV c.m. The intermediate-energy pions ($50\le T_{\pi }^{\mathrm{c}.\mathrm{m}.\mathrm{}}\le 300$ MeV) were forward and backward peaked, reflecting the individual nucleon-nucleon process in the isobar model of production. The observed cross sections were shown to be generally reproduced by an incoherent superposition of the experimental ($p$ + nucleus) cross sections.

NUCLEAR REACTIONS NaF, Cu, $\mathrm{Pb}({}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}, {\pi }^{+})X$, $\frac{E}{A}=800\mathrm{}$ MeV/nucleon; measured $\sigma (E_{\pi }, {\theta }_{\pi })$, $E_{\pi }=20-100\mathrm{}$ MeV, ${\theta }_{\pi }=30-150\mathrm{}°$.

• Received 2 February 1979

DOI:https://doi.org/10.1103/PhysRevC.20.1332