Isospin Diffusion and Equilibration for Sn+Sn collisions at E/A=35 MeV

TL;DR

This study investigates isospin diffusion and equilibration in Sn+Sn nuclear collisions at 35 MeV per nucleon, providing insights into nuclear symmetry energy and transport phenomena through experimental measurements and theoretical comparisons.

Contribution

It presents new experimental data on isospin diffusion at intermediate energies and compares these results with transport model predictions to constrain the symmetry energy's density dependence.

Findings

Data supports partial isospin equilibration in central collisions.

Results align with transport models predicting transparency.

Inconsistent with emission of fully equilibrated fragments.

Abstract

Equilibration and equilibration rates have been measured by colliding Sn nuclei with different isospin asymmetries at beam energies of E/A=35 MeV. Using the yields of mirror nuclei of 7Li and 7Be, we have studied the diffusion of isospin asymmetry by combining data from asymmetric 112Sn+124Sn and 124Sn+112Sn collisions with that from symmetric 112Sn+112Sn and 124Sn+124Sn collisions. We use these measurements to probe isospin equilibration in central collisions where nucleon-nucleon collisions are strongly blocked by the Pauli exclusion principal. The results are consistent with transport theoretical calculations that predict a degree of transparency in these collisions, but inconsistent with the emission of intermediate mass fragments by a single chemically equilibrated source. Comparisons with ImQMD calculations are consistent with results obtained at higher incident energies that provide constraints on the density dependence of the symmetry energy.