Centrality dependence of the expansion dynamics in Pb - Pb collisions at 158 A GeV/c

ABSTRACT 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 temperatur

Enhancement of hyperon production at central rapidity in 158 A GeV/c Pb-Pb collisions

Results are presented on hyperon and antihyperon production in Pb\u2013Pb, pPb and pBe collisions at 158 GeV/c per nucleon. , and yields have been measured at central rapidity and medium transverse momentum as functions of the centrality of the collision. Comparing the yields in Pb\u2013Pb 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 in the central Pb\u2013Pb collisions

Determination of the event centrality in the WA97 and NA57 experiments

ABSTRACT 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

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. (14 refs)

Results on hyperon production from NA57

ABSTRACT The NA57 experiment has been designed to study the onset of enhanced production of strange baryons and anti-baryons in Pb–Pb collisions with respect to p–Be collisions. Results from 40 and 160 A GeV/c Pb–Pb data will be shown. The main focus is on the checks of the NA57 analysis chain

Hyperon yields in Pb - Pb collisions from NA57 experiment

ABSTRACT We report results from the experiment NA57 at CERN SPS on hyperon yields at midrapidity in Pb-Pb collisions at 158 A GeV/c and 40 A GeV/c. A, Z and R yields are compared with preliminary results from the STAR. experiment at BNL

Results on 40 A GeV/c Pb - Pb collisions from the NA57 experiment

ABSTRACT The NA57 experiment has been designed to study the onset of the strange baryon and antibaryon enhancements in Pb-Pb with respect to p-Be collisions, first observed by WA97 at 160 A GeV/c. NA57 has extended the WA97 measurements to investigate the evolution of strangeness enhancement over a wider centrality range and as a function of the beam energy. Results on hyperon production in central Pb-Pb collisions at 40 A GeV/c are presented and compared with those obtained at higher energy, in the same centrality range