Study of Isoscaling with Statistical Multifragmentation Models

Source: arXiv


Different statistical multifragmentation models have been used to study isoscaling, i.e. the factorization of the isotope ratios from two reactions, into fugacity terms of proton and neutron number, R21(N,Z)=Y2(N,Z)/Y1(N,Z)=C*exp(a*N+b*Z). Even though the primary isotope distributions are quite different from the final distributions due to evaporation from the excited fragments, the values of a and b are not much affected by sequential decays. a is shown to be mainly sensitive to the proton and neutron composition of the emitting source and may be used to study isospin-dependent properties in nuclear collisions such as the symmetry energy in the equation of state of asymmetric nuclear matter.

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    • "A precise determination of the temperature achieved in nuclear reactions has become a priority in the study of heavy ion reactions. For example, recent investigations involving radioactive isotopes [1] [2] [3] [4] [5] promise to elucidate the role of the asymmetry mass terms of the nuclear equation of state through the phenomenon of isoscaling. For this, however, similar but isotopically different reactions must reach a common equilibrium temperature T at the same time. "
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    ABSTRACT: In this study the double isotope yield ratio thermometer, commonly used in heavy ion reactions, is put to the test in molecular dynamics simulations for a variety of nuclear reactions and energies. Comparing results to other estimates of the temperature and to experimental measurements, it is determined that the double isotope yield temperature indeed reflects the hot and dense phase of the reaction. Correlations between the double isotope yield temperature, the system size, beam energies, and collision times were investigated.
    Full-text · Article · Jul 2007 · Nuclear Physics A
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    • "where α and β are fitting parameters. Equations of the form of (1) can be linked, under some approximations, to primary isotope yields produced by disassembling infinite equilibrated systems in microcanonical and grand canonical ensembles [4], as well as to breakups in canonical [6] ensembles. Little reflection is needed to understand that R 21 could be affected by many reaction variables. "
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    ABSTRACT: The origin and dynamical evolution of isoscaling was studied using classical molecular dynamics simulations of ${}^{40}$Ca + ${}^{40}$Ca, ${}^{48}$Ca + ${}^{48}$Ca, and ${}^{52}$Ca + ${}^{52}$Ca, at beam energies ranging from $20 \ MeV/A$ to $85 MeV/A$. The analysis included a study of the time evolution of this effect. Isoscaling was observed to exist in these reactions from the very early primary isotope distributions (produced by highly {\it non-equilibrated} systems) all the way to asymptotic times. This indicates that isoscaling is independent of quantum effects and thermodynamical equilibrium. In summary, collision-produced isoscaling appears to be due more to the mere partitioning of the proton-neutron content of the participant nuclei, than to specific details of the reaction dynamics.
    Full-text · Article · Apr 2005 · Physical Review C
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    ABSTRACT: Calculations for a set of nuclear multifragmentation data are made using a Canonical and a Grand Canonical Model. The physics assumptions are identical but the Canonical Model has an exact number of particles, whereas, the Grand Canonical Model has a varying number of particles, hence, is less exact. Interesting differences are found. Comment: 12 pages, Revtex, and 3 postscript figures
    Preview · Article · Jun 2001 · Physical Review C
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