$\overline{\mathit{d}}$ and ${}^3\overline{\mathrm{He}}$ Production in $\sqrt{s_{\mathrm{NN}}}=130\mathit{G}\mathit{e}\mathit{V}\mathit{A}\mathit{u}+\mathit{A}\mathit{u}$ Collisions

The first measurements of light antinucleus production in $\mathrm{Au}+\mathrm{Au}$ collisions at the Relativistic Heavy-Ion Collider are reported. The observed production rates for $\overline{d}$ and ${}^3\overline{\mathrm{He}}$ 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 ${}^3\overline{\mathrm{He}}$ freeze-out volume is smaller than the $\overline{d}$ freeze-out volume.