Subthreshold pion spectra in nucleus-nucleus collision

The energy spectra of neutral pion produced in C-12-C-12 reaction at E(Lab) = 60, 74 and 84 MeV/nucleon is calculated within a modified thermal model. The nuclear mean held is taken into account through the Brueckner G-matrix effective interaction. Pion reabsorption is included through different energy and density dependence pion-nucleus optical potentials. A comparison to the experimental data shows a satisfactory agreement of pion spectra over a wide range of pion energy. Modifications are made to the pion-nucleus optical potential of Meherem et al. in order to describe pion spectra as well as pion-nucleus reactions.