Nuclear modification factor for charged pions and protons at forward rapidity in central Au plus Au collisions at 200 GeV

We present spectra of charged pions and protons in 0–10% central Au + Au collisions at View the MathML sourcesNN=200 GeV at mid-rapidity (y=0y=0) and forward pseudorapidity (η=2.2η=2.2) measured with the BRAHMS experiment at RHIC. The spectra are compared to spectra from p+pp+p collisions at the same energy scaled by the number of binary collisions. The resulting nuclear modification factors for central Au + Au collisions at both y=0y=0 and η=2.2η=2.2 exhibit suppression for charged pions but not for (anti-) protons at intermediate pTpT. The View the MathML sourcep¯/π− ratios have been measured up to pT∼3 GeV/cpT∼3 GeV/c at the two rapidities and the results indicate that a significant fraction of the charged hadrons produced at intermediate pTpT range are (anti-) protons at both mid-rapidity and η=2.2η=2.2

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

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

First results on strange baryon production from the NA57 experiment

We briefly describe the NA57 experiment, the status of the data taking, of the event reconstruction and of the physics analysis. For the physics results, we shall keep separate the study of the 40 A GeV /c Pb-Pb data (for which the bulk of reference p-Be data are still to be collected in 2001) from the study of the enhancements as a function of the number of wounded nucleons at 160 A GeV/c. (11 refs)

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