Pre-equilibrium effects in charge-asymmetric low-energy reactions

H Zheng,S Burrello,M Colonna,V Baran

doi:10.1016/j.physletb.2017.04.002

H Zheng, S Burrello + Show 2 more

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https://doi.org/10.1016/j.physletb.2017.04.002

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Abstract

We study the pre-equilibrium dipole response in the charge-asymmetric reaction Sn132+Ni58 at Elab=10 MeV/A, within a semi-classical transport model employing effective interactions for the nuclear mean-field. In particular, we adopt the recently introduced SAMi-J Skyrme interactions, whose parameters are specifically tuned to improve the description of spin–isospin properties of nuclei. Within the same framework, we also discuss pre-equilibrium nucleon emission. Our results show that both mechanisms, i.e., pre-equilibrium dipole oscillations and nucleon emission, are sensitive to the symmetry energy below the saturation density ρ0 (in the range 0.6ρ0−ρ0), to the momentum dependence of the mean-field potential and to the nucleon–nucleon cross section. Finally, a correlation analysis is applied to examine the impact of the model parameters on observables of experimental interest.

Highlights

Heavy ion reactions at energies just above the Coulomb barrier are governed, to a large extent, by one-body dissipation mechanisms
Since larger N/Z ratios signal a larger value of the symmetry energy, our results indicate that preequilibrium nucleon observables mostly probe a density region in between ρc and ρ0
The results of the covariance analysis are consistent with all the features illustrated above for the MI and momentum dependent (MD) Equation of State (EoS): the correlation functions show, in a more quantitative manner, that the observables considered in our study, apart from the expected sensitivity to the symmetry energy, are largely influenced by the momentum dependence of the effective interaction

Summary

Introduction

Heavy ion reactions at energies just above the Coulomb barrier are governed, to a large extent, by one-body dissipation mechanisms. Whereas the three SAMi-J (MD) parametrizations lead to quite similar results, in the MI case the frequency and the magnitude of the power spectrum are higher in the soft case, reflecting the larger value of the symmetry energy (see Fig. 1, panel (a)).

Results

Conclusion