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- and 3 He- 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- freeze-out volume is smaller than the d- freeze-out volume.