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HK: Physik der Hadronen und Kerne

HK 29: Physik mit schweren Ionen V / Experiment und Theorie

HK 29.1: Gruppenbericht

Donnerstag, 23. März 2000, 16:30–17:00, B 114

Collective Flow in Heavy Ion Collisions at SIS Energies — •Anton Andronic — GSI Darmstadt

We will present experimental data on collective flow, measured with the FOPI detector for the collisions Au+Au, Xe+CsI, Ru+Ru and Ni+Ni over the incident energy range from 90 MeV/nucleon to 1.7 GeV/nucleon. We will discuss two asymmetric flow observables related to the reaction plane: the directed flow and the elliptic flow. The broad detector acceptance allows us to study their dependences in different regions of the phase-space (rapidity and transverse momentum) as well as on system size, centrality and particle type.

The excitation function of the flow observables is of particular interest in the study of hot and compressed nuclear matter created in heavy ion collisions. Both directed and elliptic flow exhibit a maximum around 400 MeV/nucleon, bracketed by rapid decreases, the one towards lower energies being the most dramatic. These data have relevance for the extraction of the Equation of State (EoS) of nuclear matter and for constraining the ingredients of the transport models, like momentum dependent interactions (MDI) or in-medium nucleon-nucleon cross section. We will present systematic comparisons of both directed and elliptic flow with the IQMD transport model.