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Theses

Etude de la multifragmentation du systeme Au+Au entre 40 et 100 MeV/A: expansion et flot radial

Abstract : My thesis relates to central collisions of Au+Au at energies going from 40 to 100 MeV/A. It was pursued in the scope of an analysis of the collection and the interpretation of data obtained though the 4th campaign of measures from the INDRA multidetector. The first part for this study, related to the data collection, enabled me to rebuild the kinetic energies and the charge of the fragments detected thanks to data issued from ionisation chamber and silicium detectors of INDRA. For the first time, it has been possible to demonstrate and correct the non-linear effects appearing in INDRA's acquisition chain. At the
end of this study, I focussed on the selection of central collisions. For that purpose, and in order not to dodge the resulting interpretations on physics, I used two different methods: selection in impact parameter and PCA. A comparative study of those mathematical tools has been performed, showing instructive results.


The interpretation of the results requires the use of different codes, which in turn imply the validity of the hypothesis which need to be made (thermodinamic equilibrium, existence of a 'freeze-out' volume). The use of statistical models (SMM, MMMC) enabled to extract the size of the emitter system, named 'single source', as well as its excitation energy. The anisotropy of the fragments kinetic energy distributions enabled, depending on the incident energy of the collision, first to demonstrate the deformation of the source and second to rebuild the existing thermal and collective energies. A second comparison of the data has been performed, this time using dynamic models (QMD, CMD). At the conclusion of this study, remarques on the validity of such approaches as SMM or MMMC could be made, questioning the fundaments of the physical interpretation of the collective flow which commonly made.
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https://tel.archives-ouvertes.fr/tel-00004100
Contributor : Franck Lavaud <>
Submitted on : Tuesday, January 6, 2004 - 12:00:00 AM
Last modification on : Wednesday, October 14, 2020 - 3:42:28 AM
Long-term archiving on: : Friday, April 2, 2010 - 7:31:23 PM

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Franck Lavaud. Etude de la multifragmentation du systeme Au+Au entre 40 et 100 MeV/A: expansion et flot radial. Physique Nucléaire Théorique [nucl-th]. Université Paris Sud - Paris XI, 2001. Français. ⟨tel-00004100⟩

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