Influence of transport variables on isospin transport ratios

Abstract

The symmetry energy in the nuclear equation of state affects many aspects of nuclear astrophysics, nuclear structure, and nuclear reactions. Recent constraints from heavy ion collisions, including isospin diffusion observables, have started to put constraints on the symmetry energy below nuclear saturation density, but these constraints depend on the employed transport model and input physics other than the symmetry energy. To understand these dependencies, we study the influence of the symmetry energy, isoscaler mean field compressibility and momentum dependence, in-medium nucleon-nucleon cross sections, and light cluster production on isospin diffusion within the pBUU transport code. In addition to the symmetry energy, several uncertain issues strongly affect isospin diffusion, most notably the cross sections and cluster production. In addition, there is a difference in the calculated isospin transport ratios, depending upon whether they are computed using the isospin asymmetry of either the residue or of all forward moving fragments. Measurements that compare the isospin transport ratios of these two quantities would help place constraints on the input physics, such as the density dependence of the symmetry energy.

Excited nuclear matter at Fermi energies: From transport properties to the equation of state

“…In-medium effects, namely Pauli blocking and highorder correlations, have also been evaluated and are found to be large in the Fermi energy range; it is clear that this energy/density dependence of the nucleon-nucleon cross section has to be properly taken into account in any microscopic transport model used in the Fermi energy range. The best agreement for the in-medium factor F is the one proposed in [17], based on simple geometrical arguments. More detailed analyses of experimental data and comparisons with transport models on stopping properties are indeed welcome to confirm these results.…”

“…The best prescription is the one of ref. [17]. It is worthwhile to mention that this parametrization is rather strongly density-dependent and produces large reduction factors compared to other prescriptions [17].…”

“…3 for the incident energy range above E inc /A = 30 MeV . The 'experimental' values (symbols) are compared to standard theoretical prescriptions derived from various works and currently used in microscopic transport models [13][14][15][16][17]. We have taken the same linear density dependence as mentioned before to account for compressional effects.…”

Model dependence of isospin sensitive observables at high densities

“…In fact, there are many factors affecting nuclear reaction transport simulation, such as the initialization of colliding nuclei, the nucleon-nucleon interaction potential, nucleon-nucleon elastic and inelastic scattering cross sections, and the designs of the framework of transport model codes [19,[21][22][23][24][25]. So it is very necessary to make a dialogue between different models, to see how large the differences are on the values of isospin sensitive observables.…”

Effects of nuclear symmetry energy on η meson production and its rare decay to the dark U-boson in heavy-ion reactions

“…This is at least partially because of both the uncertainties in the physics inputs and the different numerical techniques in initializing and modeling the transport process of colliding nuclei, see, e.g., refs. [53][54][55][56][57][58] for discussions on some of the contributing factors. Thus, new and possibly more sensitive probes of the high-density behavior of nuclear symmetry energy are always useful.…”