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 stronglyinteracting with itself, and to a good

approximation thermalized.

Theorists call this matter the Theorists call this matter the Quark Gluon PlasmaQuark 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 phaseWhen energy density jumps: mixed phaseEnergy jumps do not set up pressure gradientsEnergy jumps do not set up pressure gradients

In the mixed phaseIn the mixed phase

Confinement? Mass Generation?

Why is the Study of High Density Matter Important?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’sTime 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, Because density is high, separation of gluons is small, interactions become weak:interactions become weak:

Phase space density becomes large.Phase space density becomes large.

Matter is universal for all hadrons!Matter is universal for all hadrons!

Gold-Gold Scattering at RHIC100 Gev/A in each beam

~ thousands of particles per collision

Fast particles made last becauseof Lorentz time dilation

Like Hubble expansion!

Enough energy density at RHIC to make new forms of matter!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 timeT ~ .2-.3 Fm/c

Strongly interactingQuark Gluon Plasma

sQGP

Jet Quenching

Media can reduce number of jets seenAnd can reduce back to back correlations

Requires very strong interactions!Very high initial energy density!

20-50 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 theInitial conditions

Good semi-quantitative and qualitative agreement

Color Glass Condensate Provides a Theory ofModification of Gluonic Nuclear Wavefunction

Dramatic effects seenIn 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 goodapproximation 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 providepotentially exciting ways to study this matter