Direct hadron production in ultrarelativistic heavy ion collisions

Hadrons emitted by the pre-surface layer of quark-gluon plasma (QGP) before phase transition into hadronic gas are considered as possible source of direct information about QGP. It is shown that these hadrons dominate at soft p_t if QGP is created in ultrarelativistic heavy ion collisions.Comment: 14 pages, 14 Postscript figures, submitted to Nuclear Physics

The First Magnetic Fields

We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium.Comment: Accepted for publication in Space Science Reviews. Pdf can be also downloaded from http://canopus.cnu.ac.kr/ryu/cosmic-mag1.pd

Analysis of intermediate-energy heavy-ion collisions within relativistic mean-field two-fluid model

A three-dimensional realization of the relativistic mean-field two-fluid model is described. First results of analyzing the inclusive data on the yield of nuclear fragments and pions, as well as the Plastic-Ball rapidity distributions of nuclear fragments are presented. For comparison, calculations within the conventional relativistic hydrodynamical model with the same mean fields are also performed. In spite of a pronounced sensitivity of the nuclear dynamics to the nuclear equation of state (more precisely, to the form of the mean fields), it is found that all the analyzed observables, except the pion spectra, appear to be fairly insensitive to it. The sensitivity to the nuclear stopping power is slightly higher. The orginal sensitivity of the rapidity distributions to the stopping power is smeared out by the Plastic-Ball filter and selection criterion. Nevertheless, one can conclude that the stopping power induced by the Cugnon parametrization of the nucleon-nucleon cross sections is not quite sufficient for a more adequate reproduction of the experimental data. (orig.)Available from TIB Hannover: RO 801(93-40) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman