MULTIFRAGMENTATION · Nuclear thermo-dynamics
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2006-01-20 → 2008-01-19
- EU contribution
- €151,853
- Participants
- 1
- Scheme
- EIF
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Results in brief
Final Activity Report Summary - MULTIFRAGMENTATION (Nuclear thermo-dynamics)
A method for identifying statistical equilibrium stages in the dynamics of nuclear multi-fragmentation in heavy ion collisions at intermediate energies was successfully developed. The approach has been tested for multi-fragmentation reactions induced by 129 Xe projectiles on 119 Sn targets at beam laboratory energies of 32 and 50 AMeV. The method evaluated the equilibrium expectations using the microcanonical multi-fragmentation model (MMM) and the reaction dynamics was simulated by means of the stochastic mean field (SMF) transport theory. A unique solution, corresponding to the maximum population of the system phase space, could be identified at both energies. The related phase-space configuration of the system dynamical evolution was at the level of a pre-fragment structure, i.e. of clusters in a compact form, not fully separated and still with nuclear interactions, which was not a freeze-out configuration. In the higher energy events the stage with an occupied huge part of the available phase space was still present if a considerable amount of radial collective flow was accounted for. Equilibration times and volumes could be well identified. The conclusions were that nuclear multi-fragmentation processes could be described in a statistical microcanonical frame only after a very careful choice of the fragmenting equilibrated source and with the inclusion of external collective constraints. In spite of the earlier termination of the project, due to the fellow personal reasons, the results largely achieved the research objectives of the original proposal.
Data: CORDIS, © European Union
Project objective
The statistical multifragmentation model (A. H. Raduta et al.) will be improved such as to take into account the fragment deformation degrees of freedom and to acheive realistic features specific to dynamical simulations. The modification is supposed to r estore the van der Waals shape of the nuclear phase diagram calculated via statistical models. The new version of the model and results of dynamical simlations at frezee-out will be comparatively applied in all evaluations thus contributing to the solidi ty of the obtained results. The phase diagrams of various nuclear systems will be evaluated and their evolution with size, presence or absence of the Coulomb field and isospin will be investigated. The correlation between the position of the system in the phase diagram and the average isospin of the produced fragments and isoscaling will be investigated. Scaling analyses resulting in identifying the system's critical exponents and, consequently its universality class will be performed. The sharp microcano nical heat capacity formulas recently proposed (A. H. Raduta et al.) will be paralelly applied on multifragmentation data and predictions of statistical and dynamical (BUU or QMD) simulations at various moments in time, thus drawing a solid conclusion conc erning the existence of a liquid-gas phase transition in nuclear matter. Finally, an investigation will be made concerning the relevance of the concept of freeze-out. Can one really identify a distinct, statistically equilibrated stage in the process of collision between two heavy ions? Estimators for equilibrium will be designed and their value will be measured in time for the case of dynamical simulations. Whatever the result, this kind of analysis will help in gaining realism concerning the statistical nature of nuclear multifragmentation and parameters crucial in establishing the system thermodynamics like the freeze-out volume will be identified.
Original text from CORDIS.
Participants
- LABORATORI NATIONALI DEL SUD, ISTITUTO DI FISICA NUCLEARE · CATANIACoordinatorCity levelItaly
Links
Data: CORDIS, © European Union