Density determinations in heavy ion collisions.

The experimental determination of freeze-out temperatures and densities from the yields of light elements emitted in heavy ion collisions is discussed. Results from different experimental approaches are compared with those of model calculations carried out with and without the inclusion of medium effects, which become of relevance for baryon densities above ≈5 x 10-4 fm-3. A quantum statistical (QS) model incorporating medium effects is in good agreement with the experimentally derived results at higher densities. A densitometer based on medium modified chemical equilibrium constants is proposed. [ABSTRACT FROM AUTHOR]