Blind spots of probing the high-density symmetry energy in heavy-ion collisions

TL;DR

This paper investigates the limitations of using neutron-to-proton ratios in heavy-ion collisions to probe the high-density symmetry energy, revealing potential blind spots in current experimental approaches.

Contribution

It identifies specific conditions under which the neutron/proton ratio fails to effectively constrain the high-density symmetry energy in heavy-ion collisions.

Findings

Neutron/proton ratio is ineffective when symmetry energy is less density-dependent.

Blind spots exist in current probing methods for high-density symmetry energy.

The study uses the IBUU transport model to demonstrate these limitations.

Abstract

The nuclear symmetry energy, especially at suprasaturation densities, plays crucial roles in many astrophysical studies. However, nowadays the high-density behavior of the symmetry energy is still very controversial in nuclear community. To constrain the high-density behavior of the symmetry energy, neutron-rich nuclei collisions at medium energies are considered to be one of the most effective methods. While probing the high-density symmetry energy by using heavy-ion collisions, blind spots may exist. In the framework of the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, the blind spots of probing the high-density symmetry energy by the n/p ratio in the central Au+Au reaction at 300 MeV/nucleon are demonstrated. It is found that the nucleon observable neutron to proton ratio n/p in heavy-ion collisions cannot effectively probe the high-density symmetry energy when the high-density symmetry energy is less density-dependent.