We have measured differential cross sections for the elastic scattering of charged pions from ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ into the backward hemisphere. Near the peak of the delta resonance, at ${\mathit{T}}_{\mathrm{\pi }}$=180 MeV, an angular distribution covering 114° to 168° in the laboratory extends our earlier measurements. At ${\mathit{T}}_{\mathrm{\pi }}$=142, 180, 220, and 256 MeV, we have measured an excitation function at angles approaching 170°. The cross sections for the reactions ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^{+}$${)}^3$He, ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^{\mathrm{-}}$${)}^3$H show a rise at back angles which is not seen for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^{\mathrm{-}}$${)}^3$He and ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^{+}$${)}^3$H. There is a dip in the cross sections near 130° for ${\mathit{T}}_{\mathrm{\pi }}$=180 MeV.

• Received 20 May 1994

DOI:https://doi.org/10.1103/PhysRevC.51.2534