Symmetry Energy Effects on Fusion Cross Sections

TL;DR

This study explores how the density dependence of symmetry energy influences fusion cross sections in heavy ion collisions with exotic nuclei, revealing larger fusion probabilities with more neutron-rich systems and different symmetry energy parametrizations.

Contribution

It introduces a stochastic mean field approach to analyze the impact of symmetry energy parametrizations on fusion probabilities in exotic nuclear reactions.

Findings

Larger fusion cross sections for neutron-rich systems.

Fusion probability varies with symmetry energy parametrization.

Dynamical Dipole mechanism observed in both fusion and break-up events.

Abstract

We investigate the reaction path followed by Heavy Ion Collisions with exotic nuclear beams at low energies. We will focus on the interplay between reaction mechanisms, fusion vs. break-up (fast-fission, deep-inelastic), that in exotic systems is expected to be influenced by the symmetry energy term at densities around the normal value. The evolution of the system is described by a Stochastic Mean Field transport equation (SMF), where two parametrizations for the density dependence of symmetry energy (Asysoft and Asystiff) are implemented, allowing one to explore the sensitivity of the results to this ingredient of the nuclear interaction. The method described here, based on the event by event evolution of phase space quadrupole collective modes will nicely allow to extract the fusion probability at relatively early times, when the transport results are reliable. Fusion probabilities for reactions induced by 132Sn on 64,58Ni targets at 10 AMeV are evaluated. We obtain larger fusion cross sections for the more n-rich composite system, and, for a given reaction, in the Asysoft choice. Finally a collective charge equilibration mechanism (the Dynamical Dipole) is revealed in both fusion and break-up events, depending on the stiffness of the symmetry term just below saturation.