We discuss the experimental and theoretical status of charge-symmetry violation (CSV) in the elastic scattering of ${\pi }^{+}$ and ${\pi }^{-}$ on ${}^3\mathrm{H}$ and ${}^3\mathrm{He}.$ Analysis of the experimental data for the ratios $r_1,$ $r_2,$ and R at $T_{\pi }=142,$ 180, 220, and 256 MeV provides evidence for the presence of CSV. We describe pion scattering from the three-nucleon system in terms of single- and double-scattering amplitudes. External and internal Coulomb interactions as well as the ${\Delta }_{33}$-mass splitting are taken into account as sources of CSV. Reasonable agreement between our theoretical calculations and the experimental data is obtained for $T_{\pi }=180,$ 220, and 256 MeV. For these energies, it is found that the ${\Delta }_{33}$-mass splitting and the internal Coulomb interaction are the most important contributions for CSV in the three-nucleon system. The CSV effects are rather sensitive to the choice of pion-nuclear scattering mechanisms, but at the same time, our theoretical predictions are much less sensitive to the choice of the nuclear wave function. It is found, however, that data for $r_2$ and R at $T_{\pi }=142\mathrm{}\mathrm{MeV}$ do not agree with the predictions of our model, which may indicate that there are additional mechanisms for CSV which are important only at lower energies.

• Received 22 April 2002

DOI:https://doi.org/10.1103/PhysRevC.66.054007