Pion and γ-ray bremsstrahlung in nuclear collisions at intermediate energies

The authors apply the bremsstrahlung model for pion production to symmetric nuclear collisions at energies far below the single NN threshold. There they expect this mechanism to be dominant. Once the deceleration parameter of the theory is adjusted, all main features of recent neutral-pion measurements can be explained. The parameter is close to hydrodynamical values. Since the gamma -ray bremsstrahlung also reflects the kinematics of its source, a simultaneous measurement of pion and gamma -ray bremsstrahlung can be used to further test the collision dynamics. The results of the calculations for both kinds of radiation are presented. In addition they show that for higher bombarding energies the thermally produced pions can fill the gap between the bremsstrahlung and the experimental data.