[en] In the models for energetic heavy ion reactions it is assumed that during the reaction a hot and dense nuclear matter, a fireball is formed from all or a part of nucleons of the target and projectile nuclei. The process is similar to the chemical processes leading to dynamical equilibrium. The relaxation times necessary to establish ''chemical'' equilibrium among different hadrons in hot, dense hadronic matter is deducted in a statistical model. Consequences for heavy ion collisions are discussed. The possibility of Bose-Einstein pion condensation around the break-up time of the nuclear fireball is pointed out. (D.P.)

[en] The time necessary to achieve the equilibrium ratio of strange to non strange quarks in heavy ion reactions is estimated in the framework of perturbative QCD. It is found, in the present approximation, to be much larger than the total collision time of even a central U+U collision at Esub(LAB)=2.1 GeV/nucleon bombarding energy. (author)

[en] Multi-heavy baryon yields in heavy ion collisions were calculated using an extended version of combinatoric break-up model for the description of hadron formation, and for the prediction of the coalescence probability of two or three charm quarks. The combinatoric break-up model, describing the rehadronisation of the quark-gluon matter, needs the quark and gluon content of the very high energy density matter before rehadronisation as an input. An estimation for the expected number of multi-charmed baryons (with two or three heavy quarks) in the RHIC and LHC colliders is presented. (R.P.) 7 refs.; 2 figs.; 2 tab

[en] Full texts of three contributions are presented, to the HIPAGS workshop (Brookhaven, NY, USA, March 1990), to the Quark Matter '90 Conference (Menton, France, 7-11 May 1990), and to the International Workshop on Correlations and Multiparticle Production (CAMP, Marburg, Germany, F.R., 14-16 May 1990), respectively. Their titles in the above order are: scaling in fragmentation of target spectators; energy densities, target fragmentation and pion correlations in ultrarelativistic heavy ion collisions as predicted by SPACER; on an interpretation of the GGLP formula. The papers have been indexed separately for the INIS database. (R.P.)

[en] A method is given to reconstruct the local state of a heavy ion collision which produced the detected particles. Only some particle ratios are needed; in the simplest case 2 of them determines the local state if it was in complete thermodynamic equilibrium, and the assumption is checked later. Applying the method on the available data of the E802 experiment, T ∼ 120 MeV, n/n₀ ∼ 0.4 and S/N_B ∼ 14 is obtained, which is a reasonable break-up stage. (author) 22 refs.; 7 figs

[en] The composite particle production in heavy ion collision is calculated in the framework of a hadrochemical model. A critical comparison is performed between the produced entropy and the observables. It is shown that the observed d/p ratio is not the proper quantity to determine the specific entropy, because this ratio strongly depends on the volume of the deuteron. (author)

[en] A statistical model for the time development of fireballs is presented showing the possibility of the production of pion condensatum of Bose-Einstein type. (author)

[en] The three phases of central heavy ion reactions (ignition phase, expansion phase and break up stage) are quatitatively described in a simple model based on the subsequent application of geometric picture, hadrochemical equations, hydrodynamic description. The possibility of the Bose-Einstein condensation of pions is also pointed out. (P.L.)

[en] We discuss within the framework of an analytical model central collisions between large nuclei at an intermediate energy. The model assumes three stages: the ignition stage in which thermalized nucleons are created within the reaction volume; the expansion phase in which the hot nuclear matter expands and cools; and finally, the evaporation stage in which the system disintegrates through a surface evaporation. The model provides a qualitative insight into the connections between the main physical processes throughout the collision event. (orig.)

No abstract available