The SPS ion program and the first LHC data

For the first time in the CERN history two experimental programs devoted to study nucleus-nucleus collisions at high energies are performed in parallel. In the SPS ion program, carried out by NA61/SHINE, interactions of light and medium size ions in the energy range 5-20 GeV are investigated. The program aims to discover the critical point of strongly interacting matter as well as establish properties of the onset of deconfinement. In 2010 ALICE, ATLAS and CMS at LHC recorded first data on Pb+Pb collisions at the highest energy reached up to now, 2760 GeV. This opens a new exciting area in the field of heavy ion collisions. The relation between the two programs is discussed in this presentation. Surprisingly, the first LHC results strongly support the NA49 discovery of the onset of deconfinement and thus further experimental study of nucleus-nucleus collisions at the CERN SPS.Comment: invited talk at the EPIC@LHC workshop, July 2011, Bari, Ital

On the history of multi-particle production in high energy collisions

The 60th birthday of Johann Rafelski was celebrated during the Strangeness in Quark Matter 2011 in Krakow. Johann was born in Krakow and he initiated the series of the SQM conferences. This report, which briefly presents my personal view on a history of multi-particle production in high energy collisions, is dedicated to Johann.Comment: 12 pages, 9 figures, invited talk at Strangeness in Quark Matter 2011, Krakow, Polan

Core-corona separation in the UrQMD hybrid model

We employ the UrQMD transport + hydrodynamics hybrid model to estimate the effects of a separation of the hot equilibrated core and the dilute corona created in high energy heavy ion collisions. It is shown that the fraction of the system which can be regarded as an equilibrated fireball changes over a wide range of energies. This has an impact especially on strange particle abundancies. We show that such a core corona separation allows to improve the description of strange particle ratios and flow as a function of beam energy as well as strange particle yields as a function of centrality.Comment: 10 pages, 11 figures, version accepted by PR

Critical line of the deconfinement phase transition

Phase diagram of strongly interacting matter is discussed within the exactly solvable statistical model of the quark-gluon bags. The model predicts two phases of matter: the hadron gas at a low temperature T and baryonic chemical potential muB, and the quark-gluon gas at a high T and/or muB. The nature of the phase transition depends on a form of the bag mass-volume spectrum (its pre-exponential factor), which is expected to change with the muB/T ratio. It is therefore likely that the line of the 1st} order transition at a high muB/T ratio is followed by the line of the 2nd order phase transition at an intermediate muB/T, and then by the lines of "higher order transitions" at a low muB/T.Comment: 13 pages, 6 figure