Low-Energy Pion Production at 0' with Heavy Ions from 125 to 400 MeV/Nucleon

The results of a systematic study of 0/sup 0/ pion production by heavy ions from 125 to 400 MeV/nucleon are presented. The dependence of the cross section on the mass number of the target, the energy of the beam, and the pion charge and energy are discussed. A striking feature of the data is an unexpectedly large ..pi../sup -//..pi../sup +/ ratio for pions of velocity close to the projectile velocity.