Isospin Dynamics in Peripheral Heavy Ion Collisions at Fermi Energies

TL;DR

This study investigates how isospin transport occurs in peripheral heavy ion collisions at Fermi energies, focusing on the effects of symmetry energy, mean field momentum dependence, and identifying sensitive observables.

Contribution

It provides new insights into the role of symmetry energy and mean field effects on isospin dynamics in heavy ion collisions at Fermi energies.

Findings

Isospin transport is influenced by symmetry energy and density gradients.

Reaction times are affected by the isoscalar momentum dependence of the mean field.

Two observables are identified as sensitive probes of the isovector nuclear equation-of-state.

Abstract

We present a detailed study of isospin dynamics in peripheral collisions at Fermi energies. We consider symmetric and mixed collisions of (124,112)Sn isotopes at 35 and 50 AMeV to study the isospin transport between the different reaction components (residues, gas and possibly intermediate mass fragments) and, in particular, the charge equilibration in the mixed system. We evaluate the effects of drift terms due to asymmetry and density gradients, which are directly related to the poorly known value and slope of the symmetry energy below saturation density. We verify the importance of an isoscalar momentum dependence of the mean field, which is found to influence the isospin transport since it changes the reaction times. We finally suggest two observables particularly sensitive to the isovector part of the nuclear equation-of-state: the correlation between isospin equilibration and kinetic energy loss for binary events, and the isospin content of the produced mid-rapidity fragments for neck fragmentation events.