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Type Seminar
La physique dans tous ses états
Date May 17 > 17, 2022 - 11h
Time 11h
Location GANIL, Guest House
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Study of the density dependence of the symmetry energy and cluster production

by Tom Genard

Collisions of heavy ions are the best tools at our disposal to probe nuclear matter. It allows us to reach extreme densities, giving us the possibility to constraint transport models. During the reaction, the initially at saturation density matter expands towards lower density regions in which are produced lighter fragments. Nucleons and clusters are also produced during this process, emitted during the fragmentation process, or as a result of the evaporation of excited primary fragments.

The density dependence of the symmetry energy part of the nuclear equation of state has been studied in recent years. For example, previous works on 40,48Ca+40,48Ca systems assessed the isospin diffusion, putting constraints on the symmetry energy in a lower density medium. However, this study was conducted assuming that cluster production does not affect the effect induced by this density dependence. Transport models, such as AMD (Antisymmerized Molecular Dynamics), can be improved by a study of such observables, and by a better understanding of the cluster formation process.

The aim of this thesis is thus to study that influence, by focusing on the characteristics of cluster production (energy spectra, angular distributions, multiplicities, and their correlations). Indeed, at lower densities, uniform nuclear matter becomes unstable, as inter-nucleon separation becomes comparable to nucleon-nucleon interactions, making the formation of neutron-rich fragments energetically favorable. It is possible to study this phenomenon by selecting semi-peripheral collisions. In this context, an analysis is conducted on the dynamically produced clusters, based on the assumptions of the participant-spectator model.