Strangeness and bulk freeze-out properties at RHIC

TL;DR

This study analyzes identified particle spectra from Cu+Cu collisions at RHIC energies using hydrodynamic and statistical models to understand strangeness production and freeze-out properties of the created matter.

Contribution

It provides new data bridging smaller and larger collision systems, enabling detailed analysis of strangeness equilibration onset at RHIC.

Findings

Strangeness production varies with system size and energy density.

Freeze-out parameters depend on collision energy and system size.

Data bridges gap between small and large collision systems.

Abstract

Identified charged kaon, pion, and proton spectra and ratios from sqrt(s_NN) = 200 and 62.4 GeV Cu+Cu collisions are studied with a hydro-motivated blast-wave and a statistical model framework in order to explore the strangeness production at RHIC and characterize the bulk freeze-out properties of the created system. The spectra are measured at mid-rapidity |y|<0.1 over the transverse momentum range of 0.25 < p_T < 1.2 GeV/c with particle identification derived from the ionization energy loss in the STAR Time Projection Chamber. The multi-dimensional systematic study of pi(+/-), K(+/-), p and pbar production in Cu+Cu, Au+Au, d+Au and p+p collisions is used to discuss the energy, system size and inferred energy density dependence of freeze-out parameters and strangeness production. The new data from Cu+Cu collisions bridge the gap between the smaller d+Au and larger Au+Au systems, allowing a detailed study of the onset of strangeness equilibration at RHIC.