Pioneering the Equation of State of Dense Nuclear Matter with Strange Particles Emitted in Heavy-Ion Collisions: The KaoS Experiment at GSI

Peter Senger

doi:10.3390/particles5010003

Abstract

High-energy heavy-ion collisions offer the unique possibility to study fundamental properties of nuclear matter in the laboratory, which are relevant for our understanding of the structure of compact stellar objects and the dynamics of neutron star mergers. Of particular interest are the nuclear matter equation of state (EOS), the in-medium modifications of hadrons and the degrees of freedom of matter at high densities and temperatures. Pioneering experiments exploring the EOS for symmetric matter were performed at the SIS18 accelerator of GSI, measuring, as function of beam energy, the collective flow of protons and of light fragments and subthreshold strangeness production. These data were reproduced by various microscopic transport model calculations, providing, up to date, the best constraint for the EOS of symmetric matter with an incompressibility of about 200 MeV for densities up to twice the saturation density. This article reviews the experimental results on subthreshold kaon production together with the theoretical interpretation and gives a brief outlook towards future experiments at higher densities.

Highlights

About 4 decades ago, experiments with beams of heavy nuclei such as Au and Pb started with the motivation to investigate the bulk properties of dense nuclear matter
The observation of a collective flow in heavy-ion collisions was confirmed by experiments at the SIS18 accelerator at GSI, which delivered the first Au beams in 1990
The collective flow of both protons and neutrons was measured in Au+Au collisions at 400, 600 and 800A MeV using a combination of the Four Pi (FOPI) detector and the Large Neutron Detector (LAND) [4]

Summary

Introduction

About 4 decades ago, experiments with beams of heavy nuclei such as Au and Pb started with the motivation to investigate the bulk properties of dense nuclear matter. Pioneering the Equation of State of Dense Nuclear Matter with Strange Particles Emitted in Heavy-Ion Collisions: The KaoS Experiment at GSI. The Streamer Chamber collaboration at LBL measured the excitation function of pion production in La+La collisions and estimated, from the pion yields, the fireball temperature and the potential part of the compressional energy, indicating a stiff nuclear matter equation of state (EOS) [2].

Results

Conclusion