The absorption of 239 MeV positive pions on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, N, and Ar is studied. A strong enhancement is seen in the differential cross sections in the kinematic region associated with free $\pi -p$ scattering. This enhancement is interpreted as a clear signature of initial state interactions in the absorption of pions on nuclei.

• Received 1 February 1996

DOI:https://doi.org/10.1103/PhysRevC.53.R2591