Semihard Interactions in Nuclear Collisions Based on a Unified Approach to High Energy Scattering

Our ultimate goal is the construction of a model for interactions of two nuclei in the energy range between several tens of GeV up to several TeV per nucleon in the centre-of-mass system. Such nuclear collisions are very complex, being composed of many components, and therefore some strategy is needed to construct a reliable model. The central point of our approach is the hypothesis, that the behavior of high energy interactions is universal (universality hypothesis). So, for example, the hadronization of partons in nuclear interactions follows the same rules as the one in electron-positron annihilation; the radiation of off-shell partons in nuclear collisions is based on the same principles as the one in deep inelastic scattering. We construct a model for nuclear interactions in a modular fashion. The individual modules, based on the universality hypothesis, are identified as building blocks for more elementary interactions (like e^+ e^-, lepton-proton), and can therefore be studied in a much simpler context. With these building blocks under control, we can provide a quite reliable model for nucleus-nucleus scattering, providing in particular very useful tests for the complicated numerical procedures using Monte Carlo techniques.Comment: 10 pages, no figures; Proc. of the ``Workshop on Nuclear Matter in Different Phases and Transitions'', Les Houches, France, March 31 - April 10, 199

Initial Condition for QGP Evolution from NEXUS

We recently proposed a new approach to high energy nuclear scattering, which treats the initial stage of heavy ion collisions in a sophisticated way. We are able to calculate macroscopic quantities like energy density and velocity flow at the end of this initial stage, after the two nuclei having penetrated each other. In other words, we provide the initial conditions for a macroscopic treatment of the second stage of the collision. We address in particular the question of how to incorporate the soft component properly. We find almost perfect "Bjorken scaling": the rapidity coincides with the space-time rapidity, whereas the transverse flow is practically zero. The distribution of the energy density in the transverse plane shows typically a very "bumpy" structure.Comment: 17 pages, 24 figure

Resistência à penetração e rendimento da soja após intervenção mecânica em latossolo vermelho sob plantio direto.

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A New Approach to Nuclear Collisions at RHIC Energies

We present a new parton model approach for nuclear collisions at RHIC energies (and beyond). It is a selfconsistent treatment, using the same formalism for calculating cross sections like the total and the inelastic one and, on the other hand, particle production. Actually, the latter one is based on an expression for the total cross section, expanded in terms of cut Feynman diagrams. Dominant diagrams are assumed to be composed of parton ladders between any pair of nucleons, with ordered virtualities from both ends of the ladder.Comment: 8 pages, 3 figures (proceedings Quark Matter 99

A Novel Mechanism of H^0 Di-baryon Production in Proton-Proton Interactions from Parton Based Gribov-Regge Theory

A novel mechanism of H^0 and strangelet production in hadronic interactions within the Gribov-Regge approach is presented. In contrast to traditional distillation approaches, here the production of multiple (strange) quark bags does not require large baryon densities or a QGP. The production cross section increases with center of mass energy. Rapidity and transverse momentum distributions of the H^0 are predicted for pp collisions at E_lab = 160 AGeV (SPS) and \sqrt s = 200 AGeV (RHIC). The predicted total H^0 multiplicities are of order of the Omega-baryon yield and can be accessed by the NA49 and the STAR experiments.Comment: 4 page

Time-Dependent Quasiparticle Current Density Functional Theory of X-Ray Nonlinear Response Functions

A real-space representation of the current response of many-electron systems with possible applications to x-ray nonlinear spectroscopy and magnetic susceptibilities is developed. Closed expressions for the linear, quadratic and third-order response functions are derived by solving the adiabatic Time Dependent Current Density Functional (TDCDFT) equations for the single-electron density matrix in Liouville space.Comment: 11 page

Parton-Based Gribov-Regge Theory

We present a new parton model approach for hadron-hadron interactions and, in particular, for the initial stage of nuclear collisions at very high energies (RHIC, LHC and beyond). The most important aspect of our approach is a self-consistent treatment, using the same formalism for calculating cross sections and particle production, based on an effective, QCD-inspired field theory, where many of the inconsistencies of presently used models will be avoided. In addition, we provide a unified treatment of soft and hard scattering, such that there is no fundamental cutoff parameter any more defining an artificial border between soft and hard scattering. Our approach cures some of the main deficiencies of two of the standard procedures currently used: the Gribov-Regge theory and the eikonalized parton model. There, cross section calculations and particle production cannot be treated in a consistent way using a common formalism. In particular, energy conservation is taken care of in case of particle production, but not concerning cross section calculations. In addition, hard contributions depend crucially on some cutoff, being divergent for the cutoff being zero. Finally, in case of several elementary scatterings, they are not treated on the same level: the first collision is always treated differently than the subsequent ones. All these problems are solved in our new approach