Differential isospin-fractionation in dilute asymmetric nuclear matter

TL;DR

This paper investigates how the neutron/proton ratio varies with nucleon momentum during the liquid-gas phase transition in asymmetric nuclear matter, revealing a differential isospin-fractionation effect that depends on nucleon energy.

Contribution

It introduces a self-consistent thermal model and transport model analysis to study the momentum-dependent differential IsoF in nuclear matter, providing new insights into the isovector interaction.

Findings

Neutron/proton ratio in the gas phase is smaller for energetic nucleons.

Differential IsoF effects are consistent across thermal and transport models.

Results suggest potential to extract isovector interaction details from experiments.

Abstract

The differential isospin-fractionation (IsoF) during the liquid-gas phase transition in dilute asymmetric nuclear matter is studied as a function of nucleon momentum. Within a self-consistent thermal model it is shown that the neutron/proton ratio of the gas phase becomes {\it smaller} than that of the liquid phase for energetic nucleons, although the gas phase is overall more neutron-rich. Clear indications of the differential IsoF consistent with the thermal model predictions are demonstrated within a transport model for heavy-ion reactions. Future comparisons with experimental data will allow us to extract critical information about the momentum dependence of the isovector strong interaction.