Differential cross sections for pion elastic scattering from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ at 180 MeV have been analyzed within the framework of diffraction theory. Using a phenomenological determination of the underlying pion dynamics, we deduce the ratios of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ to ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ neutron and proton densities at a radius of 4.7 fm. The results obtained show that ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ has a neutron skin in excess of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and the reverse for the proton skin, in agreement with Hartree-Fock densities, as well as previous determinations from μ x-rays and alpha scattering experiments.

• Received 13 May 1985

DOI:https://doi.org/10.1103/PhysRevC.32.1087