F. Antinori

Xi-, anti-xi-, Lambda and anti-Lambda production in sulphur - tungsten interactions at 200-GeV/c per nucleon

Abstract Multi-strange baryon and antibaryon production is expected to be a useful probe in the search for quark-gluon plasma formation. We present the transverse mass distributions of negative particles, Λ s , Λ s and Ξ − s produced in sulphur-tungsten interactions at 200 GeV/c per nucleon and give the corrected rations Λ /Λ, Ξ − /Λ and Ξ − / Λ . Our ratio Ξ − / Λ appears to be larger than that from pp interactions.

Centrality dependence of the expansion dynamics in Pb Pb collisions at 158-A-GeV/c

Two-particle correlation functions of negatively charged hadrons from Pb-Pb collisions at 158 GeV/c per nucleon have been measured by the WA97 experiment at the CERN SPS. A Coulomb correction procedure that assumes an expanding source has been implemented. Within the framework of an expanding thermalized source model the size and dynamical state of the collision fireball at freeze-out have been reconstructed as a function of the centrality of the collision. Less central collisions exhibit a different dynamics than central ones: both transverse and longitudinal expansion velocities are slower, the expansion duration is shorter and the system freezes out showing smaller dimensions and higher temperature.Two-particle correlation functions of negatively charged hadrons from Pb-Pb collisions at 158?GeV?c-1/nucleon have been measured by the WA97 experiment at the CERN SPS. A Coulomb correction procedure that assumes an expanding source has been implemented. Within the framework of an expanding thermalized source model the size and dynamical state of the collision fireball at freeze-out have been reconstructed as a function of the centrality of the collision. Less central collisions exhibit a different dynamics than central ones: both transverse and longitudinal expansion velocities are slower, the expansion duration is shorter and the system freezes out, showing smaller dimensions and higher temperature.

Enhancement of strange and multi-strange hyperons and anti-hyperons in S-S and S-W interactions at 200 GeV/c

Strange and multistrange hyperon production is expected to be enhanced in heavy ion interactions if a phase transition from hadronic matter to a quark-gluon plasma takes place. The production yields of Λs, s, Ξ−s, and s relative to the production of negative particles are presented for p-W, p-S, S-W, and S-S interactions at 200 GeV/c per nucleon and compared to those from p-Pb and Pb-Pb interactions at 158 GeV/c per nucleon. In particular, enhancements of strange and multistrange hyperons will be presented where hyperon yields are normalized to the yields of negative particles.

Results on strangeness production from the NA57 experiment

A review of recent NA57 results on K0S and hyperon production from Pb?Pb collisions at 40 and 158 A GeV/c is presented. An energy and centrality dependence of particle yields, strangeness enhancements as well as transverse mass spectra at mid-rapidity are discussed.A review of recent NA57 results on K 0 S and hyperon production from Pb-Pb collisions at 40 and 158 A GeV/c is presented. An energy and centrality dependence of particle yields, strangeness enhancements as well as transverse mass spectra at mid-rapidity are discussed.

Observation of Ω− and in sulphur-tungsten interactions at 200 GeV/c per nucleon

Abstract Multistrange baryon and antibaryon production is suggested to be a useful probe in the search for Quark-Gluon Plasma formation. We report the detection of an Ω − + Ω − signal in central S + W interactions at 200 A GeV/c and measure the ratio Ω − Ω − = 0.57±0.41 at central rapidity and p T >1.6 GeV/ c .

Ω/Ξ production ratio in S‐W

We have measured the (Ω−+Ω+)/(Ξ−+Ξ+) production ratio in central S‐W collisions to be 0.8±0.4 at central rapidity and pT≳1.6 GeV/c.

Λ and Ξ− production in proton‐tungsten interactions at 200 GeV/c per nucleon

The primary aim of the WA85 experiment is the study of strange and multistrange baryon and anti‐baryon production. Particles are detected in the kinematic window of central rapidity and pT≳1.0 GeV/c. Results on the production of Λ,u2009Λ,Ξ− and Ξ− hyperons in proton‐tungsten interactions from the 1990 run are presented and compared with the sulphur‐tungsten data.

Review of strange particle production from the WA85 Collaboration

Strange and, especially, multistrange baryon and anti‐baryon production is expected to be a useful probe in the search for Quark‐Gluon Plasma formation. A review of WA85 results on strange and multistrange particle production in SW and pW interactions at 200 GeV/c per nucleons is presented. In particular, mT distributions and relative ratios are presented for Ξ−s, Ξ−s, Λs, Λs, and K0s.

Charged kaon spectra in SW interactions at 200 GeV/c per nucleon

New results on the production of charged kaons in Sulphur‐Tungsten interactions have been obtained by the WA85 Collaboration. We present mt spectra for K+ and K− particles and the ratio <K+≳/<K−≳ calculated in the kinematic region pt≥0.9 GeV/c and 2.3≤ylab≤3.0.

Search for pentaquarks in WA97 experiment at CERN

The WA97 experiment at CERN has collected data aiming to study strangeness production in heavy ion collisions at 158 A GeV/c; p‐Be data were also taken as reference data. Here we show some results of an analysis of these p‐Be data in order to check for evidence of a recently claimed pentaquark state.