Energy Dependence of $\Lambda$ and $\bar{\Lambda }$ Production at CERN-SPS Energies

Abstract

Rapidity distributions for $\Lambda$ and $\bar{\Lambda }$ hyperons in central Pb-Pb collisions at 40, 80 and 158 A$\cdot$GeV and for ${\mathrm{K}}_s^0$ mesons at 158 A$\cdot$GeV are presented. The lambda multiplicities are studied as a function of collision energy together with AGS and RHIC measurements and compared to model predictions. A different energy dependence of the $\Lambda /\pi$ and $\bar{\Lambda }/\pi$ is observed. The $\bar{\Lambda }/\Lambda$ ratio shows a steep increase with collision energy. Evidence for a $\bar{\Lambda }/\bar{\mathrm{p}}$ ratio greater than 1 is found at 40 A$\cdot$GeV.

6 pages, 9 figures, QM2002 proceedings, submitted to Nucl. Phys. A