Quantifying the Effect of Initial Fluctuations on Isospin-Sensitive Observables from Heavy-Ion Collisions at Intermediate Energies

Abstract

Initial fluctuation is one of the ingredients that washes fingerprints of the nuclear symmetry energy on observables in heavy-ion collisions. By artificially using the same initial nuclei in all collision events, the effect of the initial fluctuation on isospin-sensitive observables, e.g., the yield ratio of free neutrons with respect to protons Nn/Np, 3H/3He yield ratio, the yield ratio between charged pions π−/π+, and the elliptic flow ratio or difference between free neutrons and protons v2n/v2p (v2n-v2p), are studied within the ultrarelativistic quantum molecular dynamics (UrQMD) model. In practice, Au + Au collisions with impact parameter b = 5 fm and beam energy Elab = 400 MeV/nucleon are calculated. It is found that the effect of the initialization on the yields of free protons and neutrons is small, while for the yield of pions, the directed and elliptic flows are found to be apparently influenced by the choice of initialization because of the strong memory effects. Regarding the isospin-sensitive observables, the effect of the initialization on Nn/Np and 3H/3He is negligible, while π−/π+ and v2n/v2p (v2n-v2p) display a distinct difference among different initializations. The fingerprints of symmetry energy on π−/π+ and v2n/v2p can be either enhanced or reduced when different initializations are utilized.

Effects of Initial Density Fluctuations on Cumulants in Au + Au Collisions at sNN = 7.7 GeV

“…It has been widely used to describe the dynamic process of collision of p + p, p + A and A + A systems over broad energy scales [30][31][32] of particles in a mean-field potential and collision term are the main ingredients of the UrQMD model. In the initialization, each nucleon is described by a Gaussian wave packet, and the centroids of the Gaussian packets are randomly distributed within a sphere of radius R. It can be calculated with an empirical formula [30,31,33]…”

Production of magnetic field due to heavy ion collisions around transition energy

“…At extreme conditions of temperature and pressure, nuclear matter has extraordinary properties [1][2][3], such as viscosity [4,5], zero friction and conductivity [6]. Apart from this, it also gives vital information about other phenomena during heavy ion collisions (HIC) like elliptical flow (v 2 ) [7][8][9][10], nuclear stopping (R P ) [11,12] and the magnetic field. HIC provide the best window for the generation of a strong magnetic field in addition to v 2 and R P .…”