Elliptic flow and the symmetry energy at supra-saturation density

TL;DR

This paper discusses how elliptic flow measurements in neutron-rich heavy-ion collisions can inform us about the symmetry energy at high densities, with initial results favoring a moderately soft to linear density dependence.

Contribution

It provides experimental insights into the density dependence of the symmetry energy using elliptic flow data and compares these with transport model predictions.

Findings

Data favor a moderately soft to linear symmetry energy density dependence

Transport models agree with experimental flow ratios and differences

High-accuracy data can improve the nuclear matter equation of state

Abstract

The elliptic flow in collisions of neutron-rich heavy-ion systems at intermediate energies emerges as an observable sensitive to the strength of the symmetry energy at supra-saturation densities. First results obtained by comparing ratios or differences of neutron and hydrogen flows with predictions of transport models favor a moderately soft to linear density dependence, consistent with ab-initio nuclear-matter theories. Comprehensive data sets of high accuracy can be expected to improve our knowledge of the equation of state of asymmetric nuclear matter.