Elastic scattering of 180-MeV ${\pi }^{+}$ and ${\pi }^{-}$ on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and tritium has been measured from ${\theta }_{\pi }(\mathrm{c}.\mathrm{m}.\mathrm{})=44\mathrm{}° \mathrm{to} 96°$. The superratio $R\equiv \frac{\left[\frac{d\sigma ({\pi }^{+}+{}_{}{}^3{}_{}{}^{}\mathrm{H})}{d\sigma ({\pi }^{-}+{}_{}{}^3{}_{}{}^{}\mathrm{He})}\right]}{\left[\frac{d\sigma ({\pi }^{+}+{}_{}{}^3{}_{}{}^{}\mathrm{He})}{d\sigma ({\pi }^{-}+{}_{}{}^3{}_{}{}^{}\mathrm{H})}\right]}$ is found to vary with angle reaching a maximum of 1.31±0.09 at ${\theta }_{\pi }=65\mathrm{}°$. The direct Coulomb effects do not account for the observed differences of $R$ from 1.0 which is the expected value on the basis of charge symmetry.

• Received 19 December 1983

DOI:https://doi.org/10.1103/PhysRevLett.52.735