Inhomogeneous freeze-out in relativistic heavy-ion collisions

Abstract

A QCD phase transition may reflect in a inhomogeneous decoupling surface of hadrons produced in relativistic heavy-ion collisions. We show that due to the non-linear dependence of the particle densities on the temperature and baryon-chemical potential such inhomogeneities should be visible even in the integrated, inclusive abundances. We analyze experimental data from Pb+Pb collisions at CERN-SPS and Au+Au collisions at BNL-RHIC to determine the amplitude of inhomogeneities.

The role of local and global strangeness neutrality at the inhomogeneous freeze-out in relativistic heavy ion collisions

“…Consequently, even the average ρ i probe higher moments of the T and µ B distributions. In [14] we showed that an inhomogeneous freeze-out model with local strangeness conservation strongly improves the description of the data at medium and top SPS energies compared to the homogeneous freeze-out. Here we showed that inducing global strangeness neutrality, results, without adding an additional parameter, in a further reduction of the χ 2 at SPS energies.…”

“…There the hadron abundances are determined by four parameters: the arithmetic means of the temperatures and chemical potentials of all domains, T and µ B , and the widths of their Gaussian distributions, δT and δµ B . Of course, the densities of strange particles depend also on the strangeness-chemical potential µ S , which we determined in [14] by imposing local strangeness neutrality. That means, the strange chemical potential in each single domain was fixed by demanding zero net strangeness there.…”

“…In [14] we introduced our model to analyze the available data from heavy-ion collisions at CERN-SPS and BNL-RHIC. There the hadron abundances are determined by four parameters: the arithmetic means of the temperatures and chemical potentials of all domains, T and µ B , and the widths of their Gaussian distributions, δT and δµ B .…”

“…In [14] we analyzed the experimental data on relative abundances of hadrons with respect to the presence of inhomogeneities on the decoupling surface. To that end we proposed a very simple and rather schematic extension of the common grand canonical freeze-out model, i.e.…”

Nucleation in the chiral transition with an inhomogeneous background

“…Nevertheless, for a system that is in the process of phase conversion after a chiral transition, one expects inhomogeneities in the chiral field configuration due to fluctuations to play a major role in driving the system to the true ground state. In fact, for high-energy heavy ion collisions, hydrodynamical studies have shown that significant density inhomogeneities may develop dynamically when the chiral transition to the broken symmetry phase takes place [6], and inhomogeneities generated during the late stages of the nonequilibrium evolution of the order parameter might leave imprints on the final spatial distributions and even on the integrated, inclusive abundances [13].…”