Low-energy pion production with 800 MeV/NNe20

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.