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Results are presented on neutral kaon, hyperon and antihyperon production in Pb-Pb and p-Be interactions at 40 GeV/c per nucleon. The enhancement pattern follows the same hierarchy as seen in the higher energy data - the enhancement increases with the strangeness content of the hyperons and with the centrality of collision. The centrality dependence of the Pb-Pb yields and enhancements is steeper at 40 than at 158 A GeV/c. The energy dependence of strangeness enhancements at mid-rapidity is discussed., Comment: 15 pages, 10 figures and 3 tables. Presented at International Conference on Strangeness in Quark Matter (SQM2009), Buzios, Rio de Janeiro, Brazil, 27 Sept - 2 Oct 2009. Submitted to J.Phys.G: Nucl.Part.Phys, one reference added

In this paper we present results on transverse mass spectra and Hanbury-Brown and Twiss correlation functions of negatively charged hadrons, which are expected to be mostly negative pions, measured in Pb-Pb collisions at 40 A GeV/c beam momentum. Based on these data, the collision dynamics and the space-time extent of the system at the thermal freeze-out are studied over a centrality range corresponding to the most central 53% of the Pb--Pb inelastic cross section. Comparisons with freeze-out conditions of strange particles and HBT results from other experiments are discussed., Comment: 29 pages, 18 figures

The transverse mass spectra of K0s, Lambda, Xi and Omega particles produced in Pb-Pb collisions at 40 A GeV/c have been studied for a sample of events corresponding to the most central 53% of the inelastic Pb-Pb cross-section. We analyze the distributions in the framework of a parameterized model inspired by hydrodynamics. The dependence of the freeze-out parameters on particle species and event centrality is discussed and comparisons with results at higher energy are shown., Comment: submitted to Journal Of Physics G: Nuclear And Particle Physics

Results are presented on hyperon and antihyperon production in Pb-Pb, pPb and pBe collisions at 158 GeV/c per nucleon. Lambda, Xi and Omega yields have been measured at central rapidity and medium transverse momentum as functions of the centrality of the collision. Comparing the yields in Pb-Pb to those in pBe interactions, strangeness enhancement is observed. The enhancement increases with the centrality and with the strangeness content of the hyperons, reaching a factor of about 20 for the Omega in the central Pb-Pb collisions., Comment: submitted to J. Phys. G.: Nucl. Part. Phys

The production at central rapidity of K0s, Lambda, Xi and Omega particles in Pb-Pb collisions at 158 A GeV/c has been measured by the NA57 experiment over a centrality range corresponding to the most central 53% of the inelastic Pb-Pb cross section. In this paper we present the rapidity distribution of each particle in the central rapidity unit as a function of the event centrality. The distributions are analyzed based on hydrodynamical models of the collisions., Comment: 15 pages, 10 figures

We present central-to-peripheral nuclear modification factors, R_CP, for the p_T distributions of K^0_S, Lambda, Anti-Lambda, and negatively charged particles, measured at central rapidity in Pb-Pb collisions at top SPS energy. The data cover the 55% most central fraction of the inelastic cross section. The K^0_S and Lambda R_CP(p_T) are similar in shape to those measured at sqrt{s_NN} = 200 GeV at RHIC, though they are larger in absolute value. We have compared our K^0_S R_CP data to a theoretical calculation. The prediction overestimates the data at p_T \approx 3-4 GeV/c, unless sizeable parton energy loss is included in the calculation., Comment: 13 pages, 5 figures, submitted to Physics Letters B

The multiplicity of charged particles in the central rapidity region has been measured by the NA57 experiment in Pb--Pb collisions at the CERN SPS at two beam momenta: 158 A GeV/{\it c} and 40 A GeV/{\it c}. The value of $dN_{ch}/d\eta$ at the maximum has been determined and its behaviour as a function of centrality has been studied in the centrality range covered by NA57 (about 50% of the inelastic cross section). The multiplicity increases approximately logarithmically with the centre of mass energy., Comment: 19 pages, 8 figures

A measurement of strange baryon and antibaryon production in Pb-Pb collisions has been carried out by the NA57 experiment at the CERN SPS, with 40 and 158 A GeV/c beam momentum. Results on $\Lambda$, $\Xi$ and $\Omega$ hyperon yields at mid-rapidity in the most central 53% of Pb-Pb collisions at 40 A GeV/c are presented and compared with those obtained at higher energy, in the same collision centrality range. The $\Lambda$ and $\Xi^-$ yields per unit rapidity stay roughly constant while those of $\Omega^-$, $\bar\Lambda$, $\bar\Xi^+$ and $\bar\Omega^+$ increase when going to the higher SPS energy. Hyperon yields at the SPS are compared with those from the STAR experiment in $\sqrt{s_{NN}}$ = 130 GeV Au-Au collisions at RHIC., Comment: 9 pages, 4 figures, 3 tables, accepted for publication in Physics Letters B

The NA57 experiment has collected high statistics, high purity samples of \PKzS and \PgL, $\Xi$ and $\Omega$ hyperons produced in Pb-Pb collisions at 158 $A$ GeV/$c$. In this paper we present a study of the transverse mass spectra of these particles for a sample of events corresponding to the most central 53% of the inelastic Pb-Pb cross-section. We analyse the transverse mass distributions in the framework of the blast-wave model for the full sample and, for the first time at the SPS, as a function of the event centrality., Comment: 22 pages, 14 figures, submitted to J. Phys. G: Nucl. Phys