Mass transport in anharmonic potentials

We investigate the effect of nuclear shell structure on the mass transport in low-energy heavy-ion collisions. The shell-correction energy leads to anharmonic driving potentials and thus, to nonlinear drift coefficients in the Fokker-Planck equation. Results for²³⁸U (7.42 MeV/nucleon)+²³⁸U are presented. The drift towards the closed Pb-shell enhances the fluctuations in the mass transport and provides an explanation for the large variances found experimentally. Local maxima in the mass distribution at the shell minima disappear due to the temperature dependence of the driving potential.     

Microscopic transport theory of heavy-ion collisions

Effects from shell structure on mass transport coefficients are studied in a schematic model. The diffusion coefficient is slightly reduced by shell effects, the reduction being less than 20% for realistic cases and reasonably high excitation energies. A much stronger effect results for the drift coefficient. This is due to the rapid variation of the shell correction energy as function of the fragmentation variable. The influence of shell effects on the time-dependent mass distributions is illustrated.     

Particle production and nonlinear diffusion in relativistic systems

The short parton production phase in high‐energy heavy‐ion collisions is treated analytically as a nonlinear diffusion process. The initial buildup of the rapidity density distributions of produced charged hadrons within τ_p? 0.25 fm/c occurs in three sources during the colored partonic phase. In a two‐step approach, the subsequent diffusion in pseudorapidity space during the interaction time of τ_int? 7‐10 fm/c (mean duration of the collision) is essentially linear as expressed in the Relativistic Diffusion Model (RDM) which yields excellent agreement with the data at RHIC energies, and allows for predictions at LHC energies. Results for d+Au are discussed in detail.     

Quark-gluon plasma formation in heavy-ion collision

To account for the non-equilibrium character of quark-gluon plasma formation in relativistic heavy-ion collisions, it is proposed to use the product of energy density ? and interaction time τ_int (rather than ?) as the critical quantity for plasma formation. In a geometrical model, τ is approximated by the transit time, and ? by the maximum energy density calculated in the center-of-mass frame. For central collisions, an analytical expression for ?·τ is given. As an example, the systems ¹⁶O + ¹⁶O and ²⁰⁸Pb + ²⁰⁸Pb are investigated as functions of c.m. energy, and their respective suitability for plasma formation is discussed.     

Time evolution of relativistic d + Au and Au + Au collisions

The evolution of charged‐particle production in collisions of heavy ions at relativistic energies is investigated as function of centrality in a nonequilibrium‐statistical framework. Precise agreement with recent d + Au and Au + Au data at = 200 GeV is found in a Relativistic Diffusion Model with three sources for particle production. Only the midrapidity source comes very close to local equilibrium, whereas the analyses of the overall pseudorapidity distributions show that the systems remain far from statistical equilibrium.     

Time-dependent condensation of bosonic potassium

The European Physical Journal D - Much effort has been devoted to describing qualitatively and quantitatively electron scattering processes due to their ever-increasing importance in many...     

Relativistic diffusion model

Evidence is presented that diffusion drives colliding many-particle systems at relativistic energies from the initial δ–functions in rapidity towards the equilibrium distribution. Analytical solutions of a linear Fokker-Planck equation represent rapidity spectra for participant protons in central heavy-ion collisions at SPS-energies accurately. Thermal equilibrium in the interaction region is not attained, nonequilibrium features persist and can account for the broad rapidity spectra. Received: 24 November 1998 / Revised version: 20 February 1999     

Nonlinear diffusion and particle production in relativistic systems

The short parton production phase in high-energy heavy-ion collisions is treated analytically as a nonlinear diffusion process. The initial buildup of the rapidity density distributions of produced charged hadrons within τ_p0.25 fm/c occurs in three sources during the colored partonic phase. In a two-step approach, the subsequent diffusion in pseudorapidity space during the interaction time of τ_int7–10 fm/c (mean duration of the collision) is essentially linear as expressed in the Relativistic Diffusion Model (RDM) which yields excellent agreement with the data at RHIC energies, and allows for predictions at LHC energies. Results for d+Au are discussed in detail.