Strange particle production in 158 and 40 AA GeV/cc Pb-Pb and p-Be collisions

Results on strange particle production in Pb-Pb collisions at 158 and 40 $A$ GeV/$c$ beam momentum from the NA57 experiment at CERN SPS are presented. Particle yields and ratios are compared with those measured at RHIC. Strangeness enhancements with respect to p-Be reactions at the same beam momenta have been also measured: results about their dependence on centrality and collision energy are reported and discussed.Comment: Contribution to the proceedings of the "Hot Quarks 2004" Conference, July 18-24 2004, New Mexico, USA, submitted to Journal of Physics G 7 pages, 5 figure

Phenotypic variation of the Aedeagus of Drosophila serido Vilela & Sene (Diptera: Drosophilidae)

Drosophila serido Vilela & Sene is a polytypic and cactophilic species with broad geographic distribution in Brazil. The morphology of the aedeagi of eight natural populations of D. serido was analyzed. Based on features of their aedeagi, populations of D. serido were discriminated with an efficiency of nearly 75%. The analysis using the Mantel test suggests that the morphological divergence of D. serido is correlated with the geographic distance among populations. There is no single cause to explain the observed pattern; therefore, the results were discussed considering the three main hypotheses to explain the aedeagus evolution: lock and key, pleiotropy and sexual selection. Alternatively, the aedeagus variability of D. serido might be related to environmental causes, such as temperature and/or host cacti.Fil:Soto, I.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Latest results from NA57.

NA57 at the CERN SPS has studied the production of strange particles in Pb-Pb and p-Be collisions. Hyperon enhancements at 40 A GeV/c are presented and compared to results at 160 GeV/c beam momenta. The momentum spectra are analysed based on hydrodynamical models and freeze-out temperature, transverse and longitudinal flow velocities are extracted. Central-toperipheral nuclear modification factors at 160 A GeV/c are calculated

Centrality dependence of strange baryon yields in Pb-Pb collisions

PoS(hep2001)248New data on strange baryon yields in Pb–Pb interactions at 158 GeV/c per nucleon are presented as a function of the collision centrality. The possible onset of a deconfined phase when the collision involves from 50 to 100 wounded nucleons is discussed