Subthreshold pion production

The Boltzmann master equation as adopted for treating equilibration in heavy ion reactions has been modified to include pion production rates from (n,n), (n,p), and (p,p) collisions. We calculate neutral pion production cross sections for reactions of 35 MeV/nucleon ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ with ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$ targets. We also calculate ${\pi }^0$ production cross sections for reactions of ${}_{}{}^{12}{}_{}{}^{}$C${+\mathrm{}}^{12}$C, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ at beam energies of 60, 74, and 84 MeV/nucleon, and of 44 MeV/nucleon ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ with ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. Results of these calculations are generally within a factor of 2 of experimental values. Compound nucleus excitations predicted for the equilibrated nuclei for the above reactions are also estimated for implications in a compound nucleus interpretation of the pion production mechanism.