Abstract
The first measurements of light antinucleus production in Au + Au collisions at the Relativistic Heavy-Ion Collider are reported. The observed production rates for (d) over bar and (3)(He) over bar are much larger than in lower energy nucleus-nucleus collisions. A coalescence model analysis of the yields indicates that there is little or no increase in the antinucleon freeze-out volume compared to collisions at CERN SPS energy. These analyses also indicate that the (3)(He) over bar freeze-out volume is smaller than the (d) over bar freeze-out volume.