Vlasov-Uehling-Uhlenbeck theory of medium energy heavy ion reactions: Role of mean field dynamics and two body collisions

Journal Article · Wed May 01 04:00:00 EDT 1985 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.31.1770· OSTI ID:5938270

Kruse, H; Jacak, B V; Molitoris, J J; Westfall, G D; Stoecker, H

The role of nonequilibrium and quantal effects in fast nucleus-nucleus collisions is studied via the Vlasov-Uehling-Uhlenbeck theory which includes the nuclear mean field dynamics, two-body collisions, and Pauli blocking. The intranuclear cascade model, where the dynamics is governed by independent NN collisions, and the Vlasov equation, where the nuclear mean field determines the collision dynamics, are also studied as reference cases. The Vlasov equation (no collision term) yields single particle distribution functions which--after the reaction--are only slightly modified in momentum space; even in central collisions, transparency is predicted. This is in agreement with the predictions of the quantal time-dependent Hartree-Fock method. In contrast, large momentum transfer is obtained when the Uehling-Uhlenbeck collision term is incorporated; then the final momentum distribution is nearly spherically symmetric in the center of mass and a well-equilibrated nuclear system is formed: the nuclei stop each other; the translational kinetic energy is transformed into randomized microscopic motion. The Vlasov-Uehling-Uhlenbeck theory is supplemented with a phase space coalescence model of fragment formation. Calculated proton spectra compare well with recent data for Ar(42, 92, and 137 MeV/nucleon) + Ca. Also the total yields of medium mass fragments are well reproduced in the present approach. The mean field dynamics without two-body collisions, on the other hand, exhibits forward peaked proton distributions, in contrast to the data. The cascade approach underpredicts the yields of low energy protons by more than an order of magnitude.

• Research Organization: National Superconducting Cyclotron Laboratory, Department of Physics and Astronomy and Department of Chemistry, Michigan State University, East Lansing, Michigan 48824
• OSTI ID: 5938270
• Journal Information: Phys. Rev. C; (United States), Journal Name: Phys. Rev. C; (United States) Vol. 31:5; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

653003* -- Nuclear Theory-- Nuclear Reactions & Scattering
653007 -- Nuclear Theory-- Nuclear Models-- (-1987)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BARYON-BARYON INTERACTIONS
BOLTZMANN-VLASOV EQUATION
CHARGED-PARTICLE REACTIONS
DIFFERENTIAL EQUATIONS
DISTRIBUTION FUNCTIONS
EQUATIONS
FUNCTIONS
HADRON-HADRON INTERACTIONS
HARTREE-FOCK METHOD
HEAVY ION REACTIONS
INTERACTIONS
MANY-BODY PROBLEM
MATHEMATICAL SPACE
MEAN-FIELD THEORY
NUCLEAR CASCADES
NUCLEAR REACTIONS
NUCLEON-NUCLEON INTERACTIONS
PARTIAL DIFFERENTIAL EQUATIONS
PARTICLE INTERACTIONS
PHASE SPACE
PROTON SPECTRA
SPACE
SPECTRA
TIME DEPENDENCE
TWO-BODY PROBLEM