Quark soup - the perfect liquid

by Ulrich Heinz (Ohio State University and CERN-PH-TH)

Wednesday 10 Oct 2007, 14:00 → 15:30 Europe/Zurich

TH Theory Conference Room (CERN)

The Relativistic Heavy Ion Collider (RHIC) was built to re-create and study in the laboratory the extremely hot and dense matter that filled our entire universe during its first few microseconds. Its operation since June 2000 has been extremely successful, and the four large RHIC experiments have produced an impressive body of data which indeed provide compelling evidence for the formation of thermally equilibrated matter at unprecedented temperatures and energy densities -- a "quark-gluon plasma". A surprise has been the discovery that this plasma behaves like an almost perfect fluid, with extremely low viscosity. Theorists had expected a weakly interacting gas of quarks and gluons, but instead we seem to have created a strongly interacting plasma liquid. I will explain the ideas and measurements which led to these conclusions, and show how they tie relativistic heavy-ion physics into other burgeoning fields of modern physics, such as strongly coupled electromagnetic plasmas and ultracold systems of trapped atoms. I'll close by reporting on recent theoretical attempts to quantify the small deviations from "perfect liquidity" seen in the experimental data.