Mechanism of pion absorption in complex nuclei

We analyze, using basic geometrical arguments, the $A$ dependence of the total pion absorption cross section, the effective number of nucleons sharing the pion momentum and energy, and the proton yields from ${\pi }^{+}$ and ${\pi }^{-}$ induced reactions. The results are consistent with the pion penetrating some distance through the nuclear volume and annihilating on a pair of nucleons.