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https://hdl.handle.net/2142/22079
Description
Title
Classical models of heavy ion collisions
Author(s)
Schlagel, Thomas Jeffrey
Issue Date
1990
Doctoral Committee Chair(s)
Pandharipande, V.R.
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Nuclear
Language
eng
Abstract
We study the effects of the nuclear equation of state (EOS) on intermediate energy heavy-ion collisions using classical microscopic models. The role of the EOS on the disassembly of expanding, hot nuclear matter, as well as the experimental data on multi-fragmentation and collective flow phenomena, are reviewed. Microscopic models used to describe heavy-ion collisions are also discussed.
Collisions between cold drops, performed at various energies, are performed using classical molecular dynamics. These drops have an EOS which is similar to that of nuclear matter. Comparisons between collisions and disassemblies of hot, liquid drops indicate that equilibrated, hot matter is formed at 80% of the equilibrium density in central collisions between equal-sized drops. The yield of small clusters is given by the $A\sbsp{c}{-\tau\sb{\rm eff}}$ power law; $\tau\sb{\rm eff}$ depends on the collision energy and has a minimum value of $\tau\sb{\rm eff} \sim$ 1.7, which is also observed in nuclear fragmentation reactions.
Two classical nucleon-nucleon interaction models are developed which have the saturation energy and density of nuclear matter, but have incompressibilities of 250 MeV and 535 MeV. Exact simulations of La+La and Au+Au collisions at 50 to 600 MeV/nucleon indicate that these models are sensitive to the interaction model at $E\sb{\rm lab} > 400$ MeV/nucleon. The results of Au+Au collisions are also compared to experimental data.
The classical nuclear models are used to test the accuracy of the Vlasov-Nordheim approximation in the classical limit, called the Vlasov-Boltzmann (VB) equation, by comparing its results with the exact results at $E\sb{\rm lab} > 400$ MeV/nucleon. VB is found to be a reasonable approximation when the known EOS and scattering cross sections ($\sigma\sb{\rm eff}$) are used. It is difficult to determine both the EOS and $\sigma\sb{\rm eff}$ by fitting the exact results. A new treatment of scattering in VB simulations, which conserves angular momentum in two-body collisions, is also discussed. Using different n-n and n-p $\sigma\sb{\rm eff}$, the VB simulations give very good agreement with the exact results.
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