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HK: Physik der Hadronen und Kerne

HK 24: Physik mit schweren Ionen II

HK 24.2: Talk

Tuesday, March 20, 2001, 16:45–17:00, E

Freeze out of expanding nuclei — •Carsten Schwarz — ALADIN-Kollaboration

Measured correlation functions of light charged particles allow to explore the thermodynamical evolution of an hot expanding source. Ejectiles from the interaction zone in central Au+Au collisions between 50 and 200 AMeV, which are subject of increasing radial flow, were detected in three high-resolution hodoscopes within the ALADIN setup at GSI. Exploiting the final state interaction between particle pairs, we determined freeze out radii which reveal the expansion of the source. The extracted values were corrected for sequential feeding, Coulomb distortions of the emitting zone, and initial correlations caused by the radial flow. The obtained radius parameters from p-a and d-a correlations are large, indicating breakup densities of about one third of normal nuclear density. However, extracted breakup radii from proton-proton pairs show a strong dependence on the beam energy and will be compared to RBUU model predictions.