Investigation of pion absorption in heavy-ion induced subthresholdπ0production

We present results from an experimental study of reabsorption effects in subthreshold ${\mathrm{\pi }}^0$ production in the reaction ${}_{}{}^{129}{}_{}{}^{}\mathrm{Xe}$ ${+}^{197}$Au at 44 MeV/nucleon. Within the picture of pion generation in nucleon-nucleon scattering we deduce, from our data and from a comparison with the systematics of production cross sections available for lighter reaction systems, information on the ${\mathrm{\pi }}^0$ absorption length in nuclear matter. For the ${\mathrm{\pi }}^0$ kinetic-energy range ≃5–100 MeV the energy-averaged ${\lambda }_{\mathrm{abs}}$ and its momentum dependence are obtained, and compared with optical-model calculations.