R. Lacey

Determination of the equation of state of dense matter

Nuclear collisions can compress nuclear matter to densities achieved within neutron stars and within core-collapse supernovae. These dense states of matter exist momentarily before expanding. We analyzed the flow of matter to extract pressures in excess of 1034 pascals, the highest recorded under laboratory-controlled conditions. Using these analyses, we rule out strongly repulsive nuclear equations of state from relativistic mean field theory and weakly repulsive equations of state with phase transitions at densities less than three times that of stable nuclei, but not equations of state softened at higher densities because of a transformation to quark matter.

Has the QCD critical point been signaled by observations at the BNL relativistic heavy ion collider

The shear viscosity to entropy ratio (

Elliptic flow: Transition from out-of-plane to in-plane emission in Au + Au collisions

\eta/s

Disappearance of elliptic flow: A new probe for the nuclear equation of state

) is estimated for the hot and dense QCD matter created in Au+Au collisions at RHIC (

Charged pion production in 2A to 8A GeV central Au plus Au collisions

\sqrt{s_{NN}}=200

Decomposition of harmonic and jet contributions to particle-pair correlations at ultrarelativistic energies

GeV). A very low value is found

Longitudinal flow of protons from (2-8)A GeV central Au+Au collisions.

\eta/s \sim 0.1

Sideward flow in Au+Au collisions between 2A and 8A GeV

, which is close to the conjectured lower bound (

Indications for a Critical End Point in the Phase Diagram for Hot and Dense Nuclear Matter

1/4\pi

Elliptic flow measurements with the PHENIX detector

). It is argued that such a low value is indicative of thermodynamic trajectories for the decaying matter which lie close to the QCD critical end point.