Recent results on (anti)nucleus and (anti)hyperon production in nucleus-nucleus collisions at CERN SPS energies

Abstract

The NA49 experiment has collected comprehensive data on particle production in nucleus-nucleus collisions over the whole SPS beam energies range, the critical energy domain where the expected phase transition to a deconfined phase is expected to occur. The latest results from Pb+Pb collisions between 20$A$ GeV and 158$A$ GeV on baryon stopping and light nuclei production as well as those for strange hyperons are presented. The measured data on $p$, $\bar{p}$, $\Lambda$, $\bar{\Lambda }$, ${\Xi }^{-}$ and ${\bar{\Xi }}^{+}$ production were used to evaluate the rapidity distributions of net-baryons at SPS energies and to compare with the results from the AGS and the RHIC for central Pb+Pb (Au+Au) collisions. The dependence of the yield ratios and the inverse slope parameter of the $m_t$ spectra on the collision energy and centrality, and the mass number of the produced nuclei ${}^{3}He$, $t$, $d$ and $\bar{d}$ are discussed within coalescence and statistical approaches. Analysis of the total multiplicity exhibits remarkable agreement between the measured yield for ${}^{3}He$ and those predicted by the statistical hadronization model. In addition, new results on $\Lambda$ and $\bar{\Lambda }$ as well as ${\Xi }^{-}$ production in minimum bias Pb+Pb reactions at 40$A$ GeV and 158$A$ GeV and central C+C, Si+Si and Pb+Pb collisions are presented. The system size dependence of the yields of these hyperons was analysed to determine the evolution of strangeness enhancement relative to elementary p+p collisions.

arXiv commentPresented at Critical Point and Onset of Deconfinement 4th International Workshop, July 9-13 2007, GSI Darmstadt,Germany}