Relativistic Heavy Ion Collider and Ultra-Dense Matter

Physics Goal: Extended Volumes of Hadronic Matter with Energy Densities Greater Than 10 Times of Atomic Nuclei Hadrons: Strongly interacting particles Experiments agree: Matter has been made exceeding this energy density which is strongly interacting with itself, and to a good approximation thermalized. Theorists call this matter the Quark Gluon Plasma

What is the Quark Gluon Plasma? The Color Glass Condensate? What is the evidence for these forms of matter? Why is it important? The Quark Gluon Plasma: Squeeze ordinary strongly interacting particles to a density much larger than the density of matter inside a typical strongly interacting particle. The quarks and gluons should become unconfined.

Pressure continuous When energy density jumps: mixed phase Energy jumps do not set up pressure gradients In the mixed phase Confinement? Mass Generation?

Why is the Study of High Density Matter Important? How is matter made from quarks and gluons? What is the high energy limit of strong interactions? How does confinement and mass arise? How do phase transitions influence cosmology? How do neutron stars and gamma ray bursters work?

What is the Color Glass Condensate? Fast moving hadron with energy E Many gluon constituents with energy e X = e/E

Color: Gluons are carry color charge Glass: Gluons at small x arise from fast moving gluons. They evolve in time very slowly because their source’s Time scale is Lorentz time dilated. Gluons are disordered. Condensate: Gluon density is as high as it can be: The phase space density is as large as possible Negative potential energy and repulsive interactions of order Because density is high, separation of gluons is small, interactions become weak: Phase space density becomes large. Matter is universal for all hadrons!

Gold-Gold Scattering at RHIC 100 Gev/A in each beam ~ thousands of particles per collision

Fast particles made last because of Lorentz time dilation Like Hubble expansion!

Enough energy density at RHIC to make new forms of matter!

Flow: Conversion of spatial gradients into momentum gradients Flow is effective at early time before mixed phase Requires very early time T ~.2-.3 Fm/c Strongly interacting Quark Gluon Plasma sQGP

Jet Quenching Media can reduce number of jets seen And can reduce back to back correlations

Requires very strong interactions! Very high initial energy density! Gev/Fm^3

Are particle distributed according to thermal distributions? Yes! Measure temperature and density at late times. A new range of parameter space to explore!

The Color Glass Condensate controls the Initial conditions Good semi-quantitative and qualitative agreement

Color Glass Condensate Provides a Theory of Modification of Gluonic Nuclear Wavefunction Dramatic effects seen In dA collisions! Agrees with semi quantitative computation. Small effect in the central region at RHIC (particles with low longitudinal momentum in the center of mass frame)

RHIC has made new forms of matter. For some of the lifetime of this matter it is to a good approximation in thermal equilibrium Theorists call this thermalized matter the Quark Gluon Plasma At early times, strong hints of a Color Glass Condensate The Future: Will characterize this matter in future experiments at RHIC Experiments at higher energies and with electrons provide potentially exciting ways to study this matter