Energy Dependence of $Λ$ and $\barΛ$ Production at CERN-SPS Energies

Abstract

Rapidity distributions for $Λ$ and $\barΛ$ hyperons in central Pb-Pb collisions at 40, 80 and 158 A$\cdot$GeV and for ${\rm K}_{s}^{0}$ 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 $Λ/π$ and $\barΛ/π$ is observed. The $\barΛ/Λ$ ratio shows a steep increase with collision energy. Evidence for a $\barΛ/\bar{\rm p}$ ratio greater than 1 is found at 40 A$\cdot$GeV.