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We present a Generalized Effective String Rope Model (GESRM) for the description of the initial state of relativistic heavy ion collisions. We start from the Effective String Rope Model (ESRM) and take into account fluctuations in the initial state following the Glauber Monte Carlo approach. Results from symmetric Au+Au collisions at different impact parameters and asymmetric A+Au head on collisions are presented at RHIC energies. The produced initial state is used as an initial condition for further hydrodynamical calculations., 28 pages, 38 figures

The evolution of dynamical perturbations is examined in nuclear multifragmentation in the frame of Vlasov equation. Both plane wave and bubble type of perturbations are investigated in the presence of surface (Yukawa) forces. An energy condition is given for the allowed type of instabilities and the time scale of the exponential growth of the instabilities is calculated. The results are compared to the mechanical spinodal region predictions.

Signatures of collective effects are studied in the quark gluon string model and in the fluid dynamical model for Au+Au collisions at 11.6A GeV/c. In the fluid dynamical model the dependence of observables on the quark-gluon plasma (QGP) formation in the equation of state is pointed out although the maximal total amount of pure QGP formed is only about 8 ${\mathrm{fm}}^{3}$ in these reactions. In contrast to the baryon rapidity distribution, the in-plane transverse flow and especially the squeeze-out effect are particularly sensitive to the EOS. In the QGSM the lifetime and extent of baryon density in strings are studied. The QGSM picture is very similar to the one obtained in the fluid dynamical model with a pure hadronic EOS.

Our aim is to study qualitatively the process of QGP cooling and hadronization. Following the statistical theory of the first order phase transitions we have to operate with such categories as nucleation rate, pre-exponential factor, surface free energy of bubbles and velocity of bubble growth. We compute the temperature, average bubble size, bubble density and fraction of space converted to the hadronic phase as a function of time. Also, we check the sensitivity of our scenarios to variations of the parameters mentioned above, as well as different schemes of QGP expansion: from longitudinal to spherical expansion. The results obtained are compared to idealized adiabatic Maxwell equilibrium scenario.

Strangeness production at the CERN Super Proton Synchrotron energies is studied within the quark-gluon string model. The observed shape of rapidity and transverse mass distributions are reproduced fairly well for both peripheral and central heavy ion collisions. However, for central collisions the model underpredicts strange particle abundances by a factor of about 2:2:4 for ${\mathit{K}}_{\mathit{S}}^{0}$, \ensuremath{\Lambda}, and \ensuremath{\Lambda}\ifmmode\bar\else\textasciimacron\fi{}, respectively. This discrepancy can be considered as a possible manifestation of collective string-string interactions similar to the formation of a color rope. Model predictions for coming experiments with the Pb beam at CERN are given.

This writeup is a compilation of the predictions for the forthcoming Heavy Ion Program at the Large Hadron Collider, as presented at the CERN Theory Institute 'Heavy Ion Collisions at the LHC - Last Call for Predictions', held from May 14th to June 10th 2007., LaTeX, 185 pages, uses iop styles; writeup of the CERN Theory Institute 'Heavy Ion Collisions at the LHC - Last Call for Predictions', held from May 14th to June 10th 2007

The final states of central Ca + Ca and Nb + Nb collisions at 400 and 1050 MeV/nucleon and at 400 and 650 MeV/nucleon, respectively, are studied with two independently developed statistical models, namely the classical microcanonical model and the quantum-statistical grand canonical model. It is shown that these models are in agreement with each other for these systems. Furthermore, it is demonstrated that there is essentially a one-to-one relationship between the observed relative abundances of the light fragments p, d, t, $^{3}\mathrm{He}$, and \ensuremath{\alpha} and the entropy per nucleon, for breakup temperatures greater than 30 MeV. Entropy values of 3.5--4 are deduced from high-multiplicity selected fragment yield data.

The time-scales of rehadronization are considered for a baryon-free QGP at RHIC and LHC energies. The non-equilibrium nucleation scenario leads to mechanical instability of the supercooled QGP phase which then may be suddenly converted in a timelike deflagration from the supercooled state to a (super)heated hadronic matter. In a model simulation such a sudden process was indeed possible and satisfied energy and momentum conservation with non-decreasing entropy. It is possible to reach a hadronic state frozen out immediately after the timelike deflagration. If a TD leads to a simultaneous hadronization and freeze-out, the conditions of a pion-flash are satisfied. This rehadronization mechanism is signalled by a reduced difference between the sidewards and outward components of Bose-Einstein correlation functions, in the observation of the free masses of the resonances in the dilepton spectra and in a clean strangeness signal of the QGP., 18 pages, uses aip.sty,revtex.sty,epsf.sty, 3 uufiled eps figures are included.

This book gives an overview of relativistic heavy ion physics with particular emphasis on those theoretical approaches which seek an understanding and explanation of the measurements. These approaches try to build a bridge between more basic theories, such as lattice QCD or nucleon-nucleon interactions, and complicated experimental observables involving a large number of particles. Thus, mainly theoretical approaches are discussed here which are strongly and directly related to experiments, and in turn they are phenomenological to some extent. These models use the available information from more complete reaction model describing the whole collision and the observables.It is suitable as a text for advanced undergraduate and graduate students - both experimentalists and theorists - for studies in the field of relativistic heavy ion physics. It may also serve as a handbook where basic concepts of reaction models can be found and the most important references for further reading are provided.

The transition from nuclear matter to quark matter in shock fronts is discussed. The relativistic shock equations are considered and applied to quark-matter production in dependence on the bag constant. The problem of shock splitting is discussed as a possible signature of the phase transition. One-dimensional hydrodynamical calculations for a two-phase system of nuclear matter and quark plasma are presented and compared to results of the shock equations for stable and unstable shock fronts.

The importance of interfragment interactions in the nuclear multifragmentation process is demonstrated in the framework of a grand canonical model. Attempts are made to find the signature of liquid-gas-phase transitions and to obtain the equation of state at subnuclear densities.

It is shown that the apparent power-law behavior of the fragment yields obtained in high-energy proton-nucleus and nucleus-nucleus collisions can be understood in terms of the coexistence of liquid and vapor phases of nuclear matter. The fragment yields are computed by calculating the disassembly of the liquid and vapor sources microanonically. Good agreement with data is obtained for a wide range of breakup densities.

The nuclear structure of zero temperature neutron star matter is investigated in the density region ϱ=1011−1014 g/cm3. The energy of a nucleus embedded into a nucleon liquid is calculated in the Thomas-Fermi approximation. We find that the beginning of the neutron drip is a first order transition of phase at the critical pressureP=2.0×1030 dyn/cm2. The resulting equation of state is compared with previous predictions and the inside structure of neutron stars are determined by integrating theOppenheimer—Volkoff equations.

Transverse-momentum data are analyzed for the presence of collective flow of nuclear matter in interactions of Au and Xe in nuclear emulsion at energies from 0.5 to 1.2 GeV/nucleon. Evidence of such flow is obtained from 122 interactions involving AgBr in nuclear emulsion by adapting a recently proposed method of transverse-momentum analysis.

A new theoretical model is introduced which is able to describe the initial compression and thermalization stage of an ultrarelativistic heavy-ion collision in a hydrodynamical three-flow picture. The first and second fluid is attributed to the nucleons of target and projectile, while a third component is introduced in order to take into account the gradual thermalization of the incoming flow. Based on relativistic transport theory, hydrodynamic equations of motion are derived for each component including transitions of target and projectile nucleons to the thermalized matter component as well as mutual deceleration accompanied with gradual heat transfer between the components. Hence, the multicomponent formalism contains the former two fluid approach as a limiting case.

Taking into account a finite conversion rate the transition of nuclear matter to quark-gluon matter and vice versa is treated in a hydrodynamical model for heavy ion collisions. For fast conversion pure quark matter is formed for laboratory energies between 4 and 10 GeV per nucleon while below 4 GeV per nucleon matter stays in a mixed phase. Due to the large amount of latent heat the temperature does not exceed k T = 160 MeV.

When nuclei collide at beam energies from several tens of MeV to several GeV per nucleon considerable disorder is generated. Nuclear fragments ranging from nucleons all the way up in mass to the target and projectile nuclei themselves have been observed experimentally. Theoretical models for the dynamics of the formation and emission of these clusters of nucleons are reviewed. Most of the models, but not all, are statistical in origin, following from the assumption that the phase space available for cluster formation and emission is the dominant factor. The entropy generated during the collision may be studied in diverse dynamical models, such as intranuclear cascade and nuclear fluid dynamics. The entropy of the system may be estimated from the measured abundances of nuclear clusters, thus providing information on the properties of hot and dense nuclear matter. Critical analysis of both conventional and exotic interpretations of the data are given.

Spherical hydrodynamical expansion and linear compression and expansion are calculated in viscous relativistic hydrodynamics. The break-up process subsequent to the hydrodynamical collective flow is also taken into account. The results lay the foundation of the blast-wave model and the comparison of the linear and spherical models with the experiment provides further evidence for the soft nuclear matter equation of state.

Mutual inhibition between neurons combined with a learning principle similar to that proposed by Hebb is shown to secure a powerful self-organizing property for neural networks. Numerical analysis reveals that the system investigated always organizes itself into the same final state from any arbitrarily chosen initial state.

In a fluid-dynamical model, the extra entropy production which arises from a nonequilibrium phase transition from nuclear to quark-gluon matter is calculated.

Recent experimental data for light particle and complex fragment emission are compared to the results of a microcanonical statistical fragmentation model. The entropy produced in the reactions is extracted by varying the breakup temperature and density. The best fit to the data is nearly independent of the temperature and density. The extracted entropy is somewhat higher for light particles than for complex fragments.

Systematic deviations from the Lorentzian approximation to the E1-giant dipole resonance (GDR) shape has been observed at the low energy side of the GDR /1,2/. The strength involved amounts to a few percent of the E1 sum rule,so this phenomenon is called pygmy resonance. A remarkable regularity has been mentioned by Lane /3/: The anomaly appears in mass number regions where empty single-particle states with l=0,1 are near the threshold. Applying the 1p-1h description the 1p-1h states containing the mentioned s or p-neutron particle states (threshold states) have unperturbed energies close to the energy of the anomaly. So these states may be saved from being coupled to the GDR. Such calculations /3,4,5/ performed in the pure 1p-1h shell model provide different amounts of the strength of the pygmy resonance as a function of the used residual interaction and basis.

Inclusive cross sections for the reactions $p+A\ensuremath{\rightarrow}p+X$ at 100 GeV are discussed in the framework of the evolution model proposed by Hwa. An exact solution to the evolution equation is found. A momentum-degradation length of 4.9 fm is inferred from the data.