Production of Charged Pions in Collisions of 450-Mev Protons with Various Nuclei

Abstract

The differential production cross sections for positive and negative pions by 450-Mev protons on Be, C, Al, Cu, Sn, Sb, Au, Pb, and U have been measured for several pion energies. The energy spectra were measured for carbon at 21.5\ifmmode^\circ\else\textdegree\fi{} and 60\ifmmode^\circ\else\textdegree\fi{} in the laboratory. The variation of cross section as a function of atomic mass number is compared to theoretical curves based on a model where the nucleus is assumed to have a surface layer of neutrons. There is good agreement between the data and the theoretical predictions. The energy spectrum at 21.5\ifmmode^\circ\else\textdegree\fi{} for carbon shows that the positive pions are produced with energies up to the energy expected for the reaction $p+{\mathrm{C}}^{12}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+{\mathrm{C}}^{13}$ with the final carbon nucleus left unexcited. The spectrum for negative pions, however, goes to zero at a lower energy, consistent with the fact that a similar two-body reaction is not possible.