Elastic Scattering of 162-MeV Pions by Nuclei

The elastic scattering of 162-MeV ${\pi }^{+}$ and ${\pi }^{-}$ by ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, Si, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ have been measured. All angular distributions, except for ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, exhibit strong diffraction patterns. Optical-model calculations with matter distributions deduced from electron scattering qualitatively reproduce the data, but better agreement for all but ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ can be obtained with suitable modifications. No substantial differences in neutron- and proton-matter radii are indicated.