Pions produced near the center-of-mass velocity in heavy-ion collisions

The cross section for producing ..pi../sup +/ and ..pi../sup -/ at velocities close to that of the center of mass was studied for the /sup 40/Ar+/sup 40/Ca reaction at E/A = 1.05 GeV. The ..pi../sup +/ and ..pi../sup -/ data show a flat plateau around y/sub c.m./ = 0. The ..pi../sup -//..pi../sup +/ ratio of 1.5 +- 0.2 is much lower than published theoretical predictions. Data were also obtained for carbon and uranium targets.