CGC GlasmaInitial Singularity

sQGP Hadron Gas

Theory Summary*

QM 2006

Shanghai, China

Art due to Tetsuo Hatsuda and Steffen Bass

(with some artistic interpretation)

* Not comprehensive

Strong correspondence with cosmology.

How can ideas be tested?

What are the new physics opportunities?

The Initial Wavefunction for High Energy

Baryon:

3 quarks

3 quarks 1 gluon

…..

3 quarks and lots of gluons

Density of Gluons Grows

becomes weak

Color Glass Condensate

Successes:

Geometric scaling in DIS

Diffractive DIS

Shadowing in dA

Multiplicity in AA

Limiting fragmentation

Long range correlations

Total cross section

Pomeron, reggeon, odderon

Break down of factorization of pp to ep? Saturated hot spots?

The Initial Singularity and the Glasma

The hadrons pass through one another:

Before the collision only transverse E and B CGC fields

Color electric and magnetic monopoles

Almost instantaneous phase change to longitudinal E and B

Topological charge density is maximal:

Anomalous mass generation

In cosmology:

Anomalous Baryogenesis

Production of gluons and quarks from melting colored glass

Before collision, stability

After collisions, unstable

Quantum fluctuations can become as big as the classical field

Quantum fluctuations analogous to Hawking Radiation

Growth of instability generates turbulence => Kolmogorov spectrum

Analogous to Zeldovich spectrum of density fluctuations in cosmology

Topological mass generation

Interactions of evaporated gluons with classical field is g x 1/g ~ 1 is

strong

Thermalization?

The Initial Singularity and the Glasma

Fluctuations in The Initial Singularity

During inflation: Fluctuations on scale larger than even horizon are made

Late times: Become smaller than even horizon => Seeds for galaxy formation

Fluctuations over many units in rapidity in initial wavefunction

Instabilities driven by momentum anisotropy

The sQGP

Energy density is high enough:

Good agreement of “well thought out” hydro

computations with radial and elliptic flow data

Very large energy loss of jets

The evidence is strong that one has made a system of quarks and

gluons which is to a good to fair approximation explained by a

Quark Gluon Plasma

Coalesence models reproduce v2 at intermediate pt.

Do they work too well?

Energy conservation?

Is its lower bound ?

Conclusion depends on initial conditions?

Do we really need huge cross sections in transport to reproduce

flow data?

Water

More evidence:

Has led some to suggest that we live in the best of all

possible worlds!

Hydro plus CGC Initial Conditions

Good description of

multiplicity and pT

distributions

Hydro +CGC + Jet quenching: good description of jets

(except for heavy quarks!)

We do not yet properly treat:

Thermalization.

Initial conditions.

Viscosity in QGP not yet treated in fully consistent way

Hadronization and coalesence not fully self consistent

Good description of v_2 when

dissipative effects in hadronic matter

are included

CGC Initial conditions without viscosity in QGP

do less well

Can and will do better:

Next generation of hydro, e. g. Spherio:

Fully 3-d with viscosity

Need more than just running codes and fitting

data!

How Perfect is the sQGP?

CGC Initial Conditions allow for higher hydro

limit.

LHC?

CGC Initial Conditions?

Large parton cross sections not required for flow.

Thermalization through mutligluon interactions?

Plasma Instabilities?

Viscosity effects are unknown, computation is theoretical challenge.

Viscous Hydrodynamics:

Becoming practical

Jet Correlations:

Cherenkov radiation and Mach cones possible, but devil in the details

Possible explanation as Sudakov form factor for jet emission by Salgado et. al?

Deflected jets al a Vitev?

Mach cones one of earliest proposals for heavy ion collisions: Greiner, Stocker and Frankfurt group

Au+Au central 0-12% ZDC

Δ2

Δ1

Mach Cone:

Radiation and scattering: No cone

Cerenkov: Wide angles

Heavy Quark Energy Loss:

Charm to bottom ratio consistent with expectation.

QCD total cross sections off from data by factor of 2-5

What is the basic energy loss mechanism:

Radiation?

Elastic scattering?

First principles computations are hard:

Results depend on low density region

Jet quenching computations not strictly perturbative.

String Theory and the sQGP.

Bad Side:

Results are for N=4 SUSY Yang Mills

No running coupling constant

No particle masses

Strict infinite coupling limit

May or may not have any qualitative relationship to QCD

No limit where theory is QCD

Good Side:

Many proponents are shamelessly enthusiastic

Can generate new ways of thinking about old problems

Was derived from string but has simple interpretation:

Mean free path must be bigger than De Broglie

wavelength

Brian Greene:

“data now emerging from the Relativistic Heavy Ion Collider

at BNL appear to be more accurately described using

string theory methods than with more traditional approaches”

<<< Is it true?

String vs Conventional Computation of Energy Density and Pressure

Conventional method is Lattice Gauge Theory:

Errors of order several %

Perturbation Theory:

25% off from ideal gas value

Naïve perturbation theory not good

String Theory: About 10% off for energy density

(scaled by number of degrees of freedom)

But………

Perturbative computations can be fixed. Good agreement for relatively weak coupling above Tc

Difference between strongly interacting and strong coupling.

String computations require coupling limit.

AdSCFT Result >

Is the coupling large?

Lattice Monte Carlo

.81 2.3

.90 1.8

1.02 .7

1.5 .4

2.0 .3

Intermediate to weakly coupled, but strongly interacting.

AdsCFT MUST be accountable to the same scientific standardsas are other computations,

or else it is not science.

Theoretical Issues:

Many problems of deep significance.

Conceptual and computational.

Issues must be scientific:

Controlled approximation

A result must be falsifiable.

“Theoretical physics must be done with

passion and enthusiasm”