| Popis: |
Doubly differential cross sections for production of positive pions ($20 \mathrm{MeV}\ensuremath{\le}{T}_{\ensuremath{\pi}}^{\mathrm{Lab}}\ensuremath{\le}100 \mathrm{MeV}$) 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 (${T}_{\ensuremath{\pi}}^{\mathrm{c}.\mathrm{m}.}\ensuremath{\le}50$ MeV) was isotropic, even 90\ifmmode^\circ\else\textdegree\fi{} peaking at \ensuremath{\sim} 15 MeV c.m. The intermediate-energy pions ($50\ensuremath{\le}{T}_{\ensuremath{\pi}}^{\mathrm{c}.\mathrm{m}.}\ensuremath{\le}300$ 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, $\mathrm{Pb}(^{20}\mathrm{Ne}, {\ensuremath{\pi}}^{+})X$, $\frac{E}{A}=800$ MeV/nucleon; measured $\ensuremath{\sigma}({E}_{\ensuremath{\pi}}, {\ensuremath{\theta}}_{\ensuremath{\pi}})$, ${E}_{\ensuremath{\pi}}=20\ensuremath{-}100$ MeV, ${\ensuremath{\theta}}_{\ensuremath{\pi}}=30\ensuremath{-}150\ifmmode^\circ\else\textdegree\fi{}$. |
