N. Carrer

Strangeness enhancement at mid-rapidity in Pb Pb collisions at 158-A-GeV/c

We study the influence of lexical subsumption on the semantic proximity of terms. By studying the semantic relation between lexically subsumed terms in an existing controlled vocabulary and those in a corpus, we formulate hypotheses on the underlying specific relations. These hypotheses enable us to propose an ordering of term variants found in the corpus, by probability of decreasing semantic proximity. Results from our experiment show that surface indices like the presence of proper names, compounds and the number of added words in a term variant are criteria for ordering the variants of the same term. The ranking obtained will enable us to form more semantically-cohesive clusters. Applications targeted are text mining, question-answering and science and technology watch.

Production of strange and multistrange hadrons in nucleus—nucleus collisions at the SPS

Abstract We report the main results from experiment WA97 on the production of strange and multistrange hadrons at midrapidity in Pb+Pb, p+Pb and p+Be collisions at 158 A GeV/ c . A comparison with some of the available models is presented.

LAMBDA , XI AND OMEGA PRODUCTION AT MID-RAPIDITY IN PB-PB AND P-PB COLLISIONS AT 158 A GEV/C

Λ, Ξ and Ω yields and transverse mass spectra measured at central rapidity in Pb-Pb and p-Pb collisions at 158 A GeV/c are presented. The yields in Pb-Pb interactions are given as a function of the collision centrality and compared with those obtained from p-Pb collisions. The dependence of hyperon yields on the centrality of the impact and on the strangeness content of the hyperon are discussed.

A study of cascade and strange baryon production in sulphur-sulphur interactions at 200 GeV/c per nucleon

Strange and multistrange baryon and antibaryon production has been studied in sulphur sulphur interactions at 200 GeV/c per nucleon at central rapidity using the CERN Omega Spectrometer. Particle production ratios and transverse mass spectra are presented for Λ, Ξ−, Λ and Ξ−.

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.

Determination of the event centrality in the WA97 and NA57 experiments

The procedure employed by the WA97 and NA57 experiments to determine the number of wounded nucleons in different Pb + Pb centrality classes is discussed. We will also compare different centrality scales and their influence on the measurement of the centrality dependence of strange particle yields.

Silicon pixel detectors for tracking in NA57

Abstract In this paper, after recalling the main features of the NA57 experiment, we describe its silicon pixel tracker.

DI-V

The first results on V0-V0 pairs, namely invariant masses and HBT correlations, obtained by the WA97 experiment in Pb-Pb collisions are presented. There is no evidence for any resonance signal.

^{0}

KS0, Λ, Ξ, Ω and negative particle h− yields and transverse mass spectra, measured at central rapidity in p-Pb and Pb-Pb collisions at 158 A GeV/c, are presented and discussed. Yields are studied as a function of the number of nucleons participating in the collision Npart, which have been estimated using the Glauber model. From p-Pb to Pb-Pb collisions the particle yields per participant increase substantially. Such an enhancement is more pronounced for multiply strange particles, and reaches an order of magnitude for Ω. For a number of participants Npart > 100, however, all yields per participant appear to be constant.

Events in Pp-Pb collisions at 158 A GeV/c

Abstract The WA94 experiment uses the production of strange particles and antiparticles to investigate the properties of hot hadronic matter created in heavy-ion interactions. Λ, Λ , Ξ− and Ξ + particle yields and transverse mass spectra are presented for pS interactions. These results are compared with those from SS interactions. Our results are also compared with those from pW and SW interactions of the WA85 experiment.