Experiment NA57 has collected high statistics, high purity samples of
Ks0, Λ, Ξ and Ω 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 about the most central
55% 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
under consideration and, for the first time at the SPS, as a function of the
event centrality.Comment: Contribution to the International Workshop on QCD: QCD@Work 2003 -
Conversano (Italy) 14-18 June 2003 (eConf C030614