Event-by-event multiplicity fluctuations in nucleus-nucleus collisions are studied within the HSD and UrQMD transport models. The scaled variances of negative, positive, and all charged hadrons in Pb+Pb at 158 AGeV are analyzed in comparison to the data from the NA49 Collaboration. We find a dominant role of the fluctuations in the nucleon participant number for the final hadron multiplicity fluctuations. This fact can be used to check different scenarios of nucleus-nucleus collisions by measuring the final multiplicity fluctuations as a function of collision centrality. The analysis reveals surprising effects in the recent NA49 data which indicate a rather strong mixing of the projectile and target hadron production sources even in peripheral collisions.PACS numbers: 25.75.Gz,

We use the ultra-relativistic quantum molecular dynamic UrQMD version 2.2 to study forward backward fluctuations and compare our results with the published data by the PHOBOS.Comment: 4 pages, 6 figures, poster presented at Strong & Electroweak Matter (SEWM2006), BNL, United States, May 10-13 200

We investigate the rapidity dependence of the elliptical flow in heavy ion collisions at 200 GeV (cms), by employing a three-dimensional hydrodynamic evolution, based on different initial conditions, and different freeze-out scenarios. It will be shown that the form of pseudo-rapidity (η) dependence of the elliptical flow is almost identical to spacetime-rapidity (η s ) dependence of the initial energy distribution, independent of the freeze-out prescriptions.

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The recently proposed baryon-strangeness correlation (CBS) is studied with a string-hadronic transport model (UrQMD) for various energies from E lab = 4 AGeV to √ s = 200 AGeV. It is shown that rescattering among secondaries can not mimic the predicted correlation pattern expected for a Quark-Gluon-Plasma. However, we find a strong increase of the CBS correlation function with decreasing collision energy both for pp and Au+Au/Pb+Pb reactions. For Au+Au reactions at the top RHIC energy ( √ s = 200 AGeV), the CBS correlation is constant for all centralities and compatible with the pp result. With increasing width of the rapidity window, CBS follows roughly the shape of the baryon rapidity distribution. We suggest to study the energy and centrality dependence of CBS which allow to gain information on the onset of the deconfinement transition in temperature and volume.Several observables [1] have been proposed throughout the last decades to study the characteristics of the highly excited matter created in heavy ions collisions, where a Quark-Gluon Plasma (QGP) is believed to be created. Among these observables, that give the opportunity to probe whether or not the system went through a phase of deconfined quarks and gluons, the ones related to fluctuations and correlations seem to be the most prospective. Fluctuation probes might be more adequate for the exploration of heavy ion reactions, because the distributions of energy density or initial temperature, isospin and particle density have strong fluctuations from event to event [2,3,4]. On the theoretical side event-by-event fluctuations where suggested to study• kinetic and chemical equilibration in nuclear collisions [5,6,7,8,9,10,11,12,13,14],• the onset of the deconfinement phase [15,16,17,18,19,20,21] • the location of the tri-critical end-point of the QCD phase transition [22,23,24] or• the formation of exotic states, like DCCs [25].On the experimental side, progress has been made by many experiments to extract momentum and particle number ratio fluctuations from heavy ion reaction: Eby-E fluctuations are actively studied in the SPS energy regime (starting from 20 AGeV on) by the NA49 group [26,27,28,29,30,31,32,33,34] and the CERES collaboration [35,36,37,38]. At RHIC energies the PHENIX [39,40,41] and STAR [42,43,44] experiments are addressing the field of single event physics.Recently a novel event-by-event observable has been introduced by Koch et al. [45], the baryon-strangeness correlation coefficient C BS . This correlation is proposed as a tool to specify the nature (ideal QGP or strongly coupled QGP or hadronic matter) of the highly compressed and heated matter created in heavy ions collisions. The idea is that depending on the phase the system is in, the relation between baryon number and strangeness will be different: On the one hand, if one considers an ideal plasma of quarks and gluons, strangeness will be carried by freely moving strange and anti-strange quarks, carrying baryon number in strict proportions. This leads to a strong correlation bet...