Effects of equation of state on hydrodynamic expansion, spectra, flow harmonics and two-pion interferometry

TL;DR

This study investigates how different equations of state influence hydrodynamic evolution and observable signatures in relativistic heavy ion collisions, finding small but notable differences across various models and experimental data.

Contribution

It provides a systematic comparison of multiple equations of state effects on hydrodynamic observables using consistent initial conditions and freeze-out scenarios.

Findings

Equations of state with different phase transition features produce similar particle spectra and flow coefficients.

Flow parameters show minimal sensitivity to the choice of equation of state.

All tested equations of state reasonably reproduce RHIC data.

Abstract

We perform an extensive study of the role played by the equation of state in the hydrodynamic evolution of the matter produced in relativistic heavy ion collisions. By using the same initial conditions and freeze-out scenario, the effects of different equations of state are compared by calculating their respective hydrodynamical evolution, particle spectra, harmonic flow coefficients $v_2$, $v_3$ and $v_4$ and two-pion interferometry radius parameters. The equations of state investigated contain distinct features, such as the nature of the phase transition, as well as strangeness and baryon density contents, which are expected to lead to different hydrodynamic responses. The results of our calculations are compared to the data recorded at two RHIC energies, 130 GeV and 200 GeV. The three equations of state used in the calculations are found to describe the data reasonably well. Differences can be observed among the studied observables, but they are quite small. In particular, the collective flow parameters are found not to be sensitive to the choice of the equation of state, whose implications are discussed.