Midrapidity $\Lambda$ and $\overline{\Lambda }$ Production in $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ Collisions at $\sqrt{s_{NN}}=130\mathrm{G}\mathrm{e}\mathrm{V}$

We report the first measurement of strange ($\Lambda$) and antistrange ($\overline{\Lambda }$) baryon production from $\sqrt{s_{NN}}=130\mathrm{G}\mathrm{e}\mathrm{V}$ $\mathrm{A}\mathrm{u}+\mathrm{A}\mathrm{u}$ collisions at the Relativistic Heavy Ion Collider (RHIC). Rapidity density and transverse mass distributions at midrapidity are presented as a function of centrality. The yield of $\Lambda$ and $\overline{\Lambda }$ hyperons is found to be approximately proportional to the number of negative hadrons. The production of $\overline{\Lambda }$ hyperons relative to negative hadrons increases very rapidly with transverse momentum. The magnitude of the increase cannot be described by existing hadronic string fragmentation models alone.