Etude d'extensions stochastiques d'équations cinétiques pour la production de kaons sous le seuil dans les collisions d'ions lourds

Abstract : Kaon production in heavy-ion collisions at bombarding energies below the nucleon-nucleon threshold is highly interesting. It can be related to the time evolution of the nuclear density during the collision which, in turn, could provide information on the Equation of State (EOS) of the nuclear matter at high densities and/or high temperatures. It could also help elucidating the question of whether subthreshold kaon production is a collective process or can still be explained by elementary baryon-baryon processes. In a first step, we give a review of models used for studying kaon production and we discuss the different parametrizations of the elementary kaon production cross-sections. In the second step, we study kaon production in the framework of the nuclear Boltzmann equation. This study shows that kaon production is very sensitive to the elementary cross-sections but not sufficiently to the mean field to determine accurately the EOS. We have then studied kaon production in the framework of the Boltzmann-Langevin equation. This approach goes beyond the average description of the Boltzmann equation by incorporating fluctuations due to high order correlations. To simulate this equation, we have developed an original method based on the projection of fluctuations on multipole moments of the momentum distribution. This study shows that large fluctuations appear in the early stages of the collision. It also shows that fluctuations, when incorporated into the equation of motion, substantially increase the kaon production cross-sections. In the last part, we have developed a model based on the results of the simulations of Boltzmann and Boltzmann-Langevin approaches to study kaon production far below the threshold. This model allows to evaluate kaon production cross-sections at energies as low as 100 MeV/n. Our results for the Ca + Ca collision are in good agreement with experimental data
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M. Belkacem-Bouricha. Etude d'extensions stochastiques d'équations cinétiques pour la production de kaons sous le seuil dans les collisions d'ions lourds. Physique Nucléaire Expérimentale [nucl-ex]. Université de Caen, 1992. Français. ⟨in2p3-00010194⟩

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