Lambda production in central Pb+Pb collisions at CERN-SPS energies

Abstract

In this paper we present recent results from the NA49 experiment for $Λ$ and $\barΛ$ hyperons produced in central Pb+Pb collisions at 40, 80 and 158 A$\cdot$GeV. Transverse mass spectra and rapidity distributions for $Λ$ are shown for all three energies. The shape of the rapidity distribution becomes flatter with increasing beam energy. The multiplicities at mid-rapidity as well as the total yields are studied as a function of collision energy including AGS measurements. The ratio $Λ/π$ at mid-rapidity and in 4$π$ has a maximum around 40 A$\cdot$GeV. In addition, $\barΛ$ rapidity distributions have been measured at 40 and 80 A$\cdot$GeV, which allows to study the $\barΛ$/$Λ$ ratio.