Omega and AntiOmega production in Pb+Pb and p+p collisions at 30, 40 and 158 AGeV

We report preliminary results on Omega and AntiOmega production in central Pb+Pb collisions at 30, 40 and 158 AGeV and p + p interactions at 158 GeV. The midrapidity AntiOmega/Omega ratio is estimated to be 0.45 +- 0.05 and 0.41 +- 0.18 for central Pb+Pb collisions at 158 and 40 AGeV, respectively. The corresponding value for 158 GeV p+p interactions is 0.67 +- 0.62. For central Pb+Pb collisions at 158 AGeV fully corrected distributions are obtained. The inverse slope parameters of the transverse mass spectrum and total yields are T(Omega) = 276 +- 23 MeV, = 0.47 +- 0.07 and T(AntiOmega) = 285 +- 39 MeV, = 0.15 +- 0.02.Comment: Contribution to the proceedings of "Strangeness in Quark Matter 2003" (March 2003, Atlantic Beach NC, USA), to be published in Journal of Physics G., 6 pages, 6 figure

Strangeness production at SPS energies

We present a summary of measurements of strange particles performed by the experiment NA49 in central and minimum bias Pb+Pb collisions in the beam energy range 20A - 158A GeV. New results on Xi production in central Pb+Pb collisions and on Lambda, Xi production in minimum bias collisions are shown. Transverse mass spectra and rapidity distributions of strange particles at different energies are compared. The energy dependence of the particle yields and ratios is discussed. NA49 measurements of the Lambda and Xi enhancement factors are shown for the first time.Comment: Submitted to J. Phys. G (Proceedings of the 9th International Conference on Strangeness in Quark Matter, Los Angeles, USA, March 26-31, 2006). 9 pages, 9 figure

Multistrange Hyperon Production in Pb+Pb collisions at 30, 40, 80 and 158 A⋅\cdotGeV

A non-monotonic energy dependence of the $K^{+} / \pi^{+}$ ratio with a sharp maximum close to 30 A$\cdot$GeV is observed in central Pb+Pb collisions. Within a statistical model of the early stage, this is interpreted as a sign of the phase transition to a QGP, which causes a sharp change in the energy dependence of the strangeness to entropy ratio. This observation naturally motivates us to study the production of multistrange hyperons ($\Xi$, $\Omega$) as a function of the beam energy. Furthermore it was suggested that the kinematic freeze-out of $\Omega$ takes place directly at QGP hadronization. If this is indeed the case, the transverse momentum spectra of the $\Omega$ directly reflect the transverse expansion velocity of a hadronizing QGP. In this report we show preliminary NA49 results on $\Omega^{-}$ and $\bar{\Omega}^{+}$ production in central Pb+Pb collisions at 40 and 158 A$\cdot$GeV and compare them to measurements of $\Xi^{-}$ and $\bar{\Xi}^{+}$ production in central Pb+Pb collisions at 30, 40, 80 and 158 A$\cdot$GeV.Comment: Presented at 25th International School of Nuclear Physics, Erice, Italy, to be published in Progress in Particle and Nuclear Physics, 3 pages, 4 figure