ΛProduction near Threshold in Central Nucleus-Nucleus Collisions

$\Lambda$'s produced in central collisions of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+KC1 at 1.8-GeV/u incident energy were detected in a streamer chamber by their charged-particle decay. For central collisions with impact parameters $b<\mathrm{}2.4\mathrm{}$ fm the $\Lambda$ production cross section is 7.6±2.2 mb. A calculation in which $\Lambda$ production occurs in the early stage of the collision qualitatively reproduces the results but underestimates the transverse momenta. An average $\Lambda$ polarization of -0.10±0.05 is observed.