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

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 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.
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Metadaten
Author:Hans Kruse, Barbara V. Jacak, Joseph J. Molitoris, Gary D. Westfall, Horst Stöcker
URN:urn:nbn:de:hebis:30-27582
URL:http://link.aps.org/abstract/PRC/v31/p1770
Parent Title (German):Physical review C
Document Type:Article
Language:English
Date of Publication (online):2006/06/12
Year of first Publication:1985
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2006/06/12
Volume:31
Issue:5
Pagenumber:5
First Page:1770
Last Page:1774
Note:
PACS: 24.10.-i, 25.70.-z
HeBIS PPN:187241619
Institutes:Physik
Dewey Decimal Classification:530 Physik
Sammlungen:Universitätspublikationen
Licence (German):License Logo Veröffentlichungsvertrag für Publikationen

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