Pion absorption on nuclei at 65 MeV

Proton-proton and proton-neutron angular correlations as well as proton and deuteron inclusive spectra from pion absorption on C, Al, Cu, and Ta were measured at $T_{\pi }$=65 MeV. We compared the results with the prediction of the intranuclear cascade model, assuming that pion absorption proceeds only through two-nucleon absorption processes. The differential cross sections of the (${\pi }^{+}$,p) and (${\pi }^{+}$,pp) reactions were fairly well reproduced by the calculation in a wide angular range. Ratios R of the pion absorption cross section on a pn pair to that on a pp or nn pair, were in agreement between the inclusive and exclusive measurements for C and Al, but for Cu, the inclusive measurement gave a smaller R value. The internuclear cascade calculations for the (${\pi }^{\pm }$,pn) and (${\pi }^{\mathrm{-}}$,pp) reactions revealed the importance of the pion charge exchange process before absorption, even at $T_{\pi }$=65 MeV.