Study of the transverse mass spectra of strange particles in Pb-Pb collisions at 158 A GeV/c

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. Phy

Analysis of the spectator-angular distribution in the light-nuclei reactions

Angular distributions of spectator particles in dp and 4Hep reactions in the region of a few GeV have been studied. Significant asymmetries of the spectator particle distributions have been observed for reactions where π-mesons are produced in the final state. Results of calculations in the framework of a spectator model taking into account the nuclear wave function, flux factor and the energy dependence of the NN elementary cross-sections, have been compared to experimental data. A good agreement has been observed for the fragments momenta, where the one-pole mechanism dominates

Spin-dependent \mth{np \rightarrow pn} amplitude estimated from \mth{dp\rightarrow ppn}

An estimation of the spin-dependent part of the $np\to pn$ charge exchange amplitude was made on the basis of $dp\to (pp)n$ data, taken at 1.67 GeV/$c$ per nucleon in a full solid-angle arrangement. The $np\to pn$ amplitude turned out to be entirely spin-dependent. This result shows new possibilities for experiments using polarized deuteron beams and polarized proton targets