Pion elastic scattering onSi28atTπ=400 MeV

Experimental differential cross sections for ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ elastic scattering on ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ at an incident pion energy of 400 meV are reported. The data fall above the predictions of a calculation using a momentum-space first-order optical potential. The behavior is similar to earlier results for pion scattering at ${\mathit{T}}_{\mathrm{\pi }}$=672 meV and to ${\mathit{K}}^{+}$ nucleus scattering in this energy range, suggesting that there may be a common origin for the observed discrepancy that is not yet understood.