Symmetry energy and nucleon-nucleon cross sections

TL;DR

This paper extends a nuclear collision model to include isospin-dependent nucleon-nucleon cross sections derived from the nuclear matter equation of state, highlighting the impact of symmetry energy on collision observables.

Contribution

It introduces a method to estimate isospin-dependent cross sections using the Van der Waals form of the nuclear matter equation of state, enhancing the modeling of nuclear collisions.

Findings

Symmetry energy significantly affects nucleon emission ratios.

Observable dependencies on symmetry energy can help constrain its density dependence.

The model provides a tool for testing nuclear equations of state in astrophysics.

Abstract

The extension of the Boltzmann-Uehling-Uhlenbeck model of nucleus-nucleus collision is presented. The isospin-dependent nucleon-nucleon cross sections are estimated using the proper volume extracted from the equation of state of the nuclear matter transformed into the form of the Van der Waals equation of state. The results of such simulations demonstrate the dependence on symmetry energy which typically varies strongly from the results obtained using only the isospin-dependent mean-field. The evolution of the n/p multiplicity ratio with angle and kinetic energy, in combination with the elliptic flow of neutrons and protons, provides a suitable set of observables for determination of the density dependence of the symmetry energy. The model thus provides an environment for testing of equations of state, used for various applications in nuclear physics and astrophysics.