Dynamics of cluster production in Xe+Sn collisions between 32 and 150 A MeV
Description
Heavy-ion collisions are the best tools we have at our disposal for studying nuclear matter. In particular, the study of clusters, light aggregates of nucleons, is a key ingredient in understanding and constraining the parameters of the equation of state of nuclear matter. During these collisions, the system undergoes compression, followed by expansion. A significant number of light and intermediate clusters are emitted during these collisions. But we don't know whether they are formed during the system's compression or expansion phase. Several transport models nevertheless attempt to predict cluster formation, based on dynamical theories. These are based on a variety of assumptions and approximations, as there is no single theoretical framework for studying dense matter. Understanding cluster production is also crucial when modeling compact astrophysical objects, such as neutron stars and type II supernovae. The analysis carried out during this thesis will focus on the characterization of clusters formed during Xe+Sn collisions, at intermediate incident energies between 32 and 150 A MeV. These data were collected at GSI and GANIL, using the INDRA multidetector. They are compared with a semi-classical model, ELIE. First, we will characterize the participant zone in Xe+Sn collisions, at an incident energy of 100 A MeV. This zone emits clusters, which may reflect the conditions of the nuclear environment at the time of their formation. Isospin effects will be of particular interest. We will compare cluster production for four systems : 129,124Xe + 112,124Sn. The total mixing of target and projectile contributions is observed, based on a production hierarchy that depends on the total N/Z ratio of the system. A significant effect of centrality on the production of heavy clusters is also observed. The second part of this analysis focuses on the dynamic characterization of clusters in the participant zone. Compression of the participant zone during collision results in radial expansion, contributing to the transverse kinetic energy of the clusters. In our analysis, we postulate that this contribution is the only one dependent on density. It can be extracted from the kinetic energy, and is used to estimate the maximum density reached during the collision. It is calculated here for 129,136Xe + 124Sn systems from 32 to 150 A MeV. The maximum densities calculated far exceed the saturation density, reaching up to 2 times the saturation density for an incident energy of 150 A MeV. These results are compatible with those of published transport models (BNV, pBUU, TDHF). A maximum density calculation, performed with BUU(at)VECC-McGill for our studied systems, reproduces our results beyond 65 A MeV. These experimental results, characterizing clusters and their production, can impose important constraints on transport models. (author)
Abstract (French)
Les collisions d'ions lourds sont les meilleurs outils dont nous disposons pour etudier la matiere nucleaire. En particulier, l'etude des clusters, des agregats legers de nucleons, constitue un ingredient cle a la comprehension et a la contrainte des parametres de l'equation d'etat de la matiere nucleaire. Lors de ces collisions, le systeme subit une compression, suivi d'une expansion. Une quantite importante de clusters legers et intermediaires est emise lors de ces collisions. Mais nous ne savons pas s'ils sont formes lors de la phase de compression, ou d'expansion, du systeme. Plusieurs modeles de transport tentent neanmoins de predire la formation des clusters, a partir de theories dynamiques. Elles reposent sur diverses hypotheses et approximations, car il n'existe pas de cadre theorique permettant d'etudier la matiere dense. La comprehension de la production de clusters est egalement cruciale lors de la modelisation d'objets astrophysiques compacts, comme les etoiles a neutrons et les supernovae de type II. L'analyse realisee lors de cette these portera sur la caracterisation des clusters formes lors de collisions de Xe+Sn, a des energies incidentes intermediaires, entre 32 et 150A MeV. Ces donnees ont ete collectees a GSI et au GANIL, par le multidetecteur INDRA. Elles sont comparees a un modele semi-classique, ELIE. Dans un premier temps, nous allons caracteriser la zone participante lors de collisions de Xe+Sn, a une energie incidente de 100 A MeV. Cette zone emet des clusters, qui peuvent refleter les conditions du milieu nucleaire lors de leur formation. Les effets d'isospin vont etre d'interet particulier. Nous allons ainsi comparer la production de clusters pour quatre systemes : 129,124Xe + 112,124Sn. Le melange total des contributions provenant de la cible et du projectile est observe, a partir d'une hierarchie de production dependant du rapport N/Z total du systeme. Un effet important de la centralite sur la production de clusters lourds est egalement observe. La seconde partie de cette analyse porte sur la caracterisation dynamique des clusters dans la zone participante. La compression de la zone participante lors de la collision se traduit par un mouvement d'expansion radial, contribuant a l'energie cinetique transverse des clusters. Dans notre analyse, nous postulons que cette contribution est la seule dependante de la densite. Elle peut etre extraite de l'energie cinetique, et permet d'estimer la densite maximale atteinte lors de la collision. Elle est ici calculee pour des systemes 129,136Xe + 124Sn de 32 a 150 A MeV. Les densites maximales calculees depassent largement la densite de saturation, atteignant jusqu'a 2 fois la densite de saturation pour une energie incidente de 150 A MeV. Ces resultats sont compatibles avec les resultats de modeles de transports publies (BNV, pBUU,TDHF). Un calcul de la densite maximale, realise avec BUU(at)VECC-McGill pour nos systemes etudies, reproduit nos resultats au-dela de 65 A MeV. Ces resultats experimentaux, caracterisant les clusters et leur production, peuvent imposer des contraintes importantes sur les modeles de transport
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Additional details
Additional titles
- Original title (French)
- Dynamique de production des clusters dans les collisions de Xe+Sn entre 32 et 150 A MeV
Publishing Information
- Imprint Pagination
- 147 p.
- Report number
- FRCEA-TH--16747
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 55034269
- Subject category
- S73: NUCLEAR PHYSICS AND RADIATION PHYSICS;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- EQUATIONS OF STATE; HEAVY IONS; ION COLLISIONS; NUCLEAR MATTER; NUCLEAR MODELS; NUCLEAR PHYSICS; TIN ISOTOPES; XENON ISOTOPES
- Descriptors DEC
- CHARGED PARTICLES; COLLISIONS; EQUATIONS; IONS; ISOTOPES; MATHEMATICAL MODELS; MATTER; PHYSICS
Optional Information
- Notes
- 126 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses