Lambda production in central Pb $plus$ Pb collisions at CERN-SPS energies

Abstract

In this paper we present recent results from the NA49 experiment for $\\Lambda$ and $\\bar{\\Lambda}$ hyperons produced in central Pb+Pb collisions at 40, 80 and 158 A$\\cdot$GeV. Transverse mass spectra and rapidity distributions for $\\Lambda$ 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 $\\Lambda/\\pi$ at mid-rapidity and in 4$\\pi$ has a maximum around 40 A$\\cdot$GeV. In addition, $\\bar{\\Lambda}$ rapidity distributions have been measured at 40 and 80 A$\\cdot$GeV, which allows to study the $\\bar{\\Lambda}$/$\\Lambda$ ratio.