Precision Probes for Hot QCD Matter

Rainer FriesTexas A&M University & RIKEN BNL

QCD Workshop, Washington DCDecember 15, 2006

QCD DC 2006 2 Rainer Fries

Precision Probes

Overwhelming evidence for a new high-T state of nuclear matter at RHIC: (s)QGP Different from normal nuclear matter Probably no weakly interacting gas

What are the properties of this new state? Equation of state, transport properties, phase transitions

Precision probes: Rare (external) probes interacting with the plasma Sufficient control of initial condition I

Hard QCD probes & electromagnetic probes

Theory: Calculate framework (including initial state I) Model jet-medium interaction

Tests Suggest Scientists Have Found Big Bang Goo

RHIC Scientists Serve Up “Perfect” Liquid

New state of matter m

ore remarkable than predicted --

raising many new questions

B

NL Press Release

I F

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Jets QCD jets as probes: controlled by pQCD.

Paradigm: jet quenching through radiative energy loss (BDMPS, GLV, AMY, SW etc.) Success: jet quenching prediction confirmed! Transport coefficient

Challenges for models: Inclusive quantities: not very sensitive to v2 for jets? Path dependence? Heavy quark energy loss? Quark vs gluon energy loss? Response of the medium?

Theory framework in most cases: Leading order pQCD + your

favorite fireball model

2ˆ q

q̂

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PHENIX preliminary

New Developments The age of tomography? Not yet, but …

New ways to think about energy loss: Collisional? Non-perturbative? New data: ridge, cone, … Collective medium response? Which modes? What is jet, what is medium? Thermalization?

Casalderrey-Solana QM06

Mediumaway

near

deflected jets

away

near

Medium

mach cone

1

3

12

1

2 12

13

The Cone

The Ridge

3-particle correlations

STAR preliminary

STAR

ppAuAu

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E&M Probes Penetrating probes: photons + dileptons carry

information from deep inside the fireball and/or early times Access temperature via thermal

emission and jet-photon conversion Not yet well constrained

Need new observables Correlations v2: jet-medium photons negative Not observed (?) No radiative energy loss?

Frantz QM06

PHENIX preliminary

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The Future Go less and less inclusive to gain sensitivity

More correlations: h-h, -h, -jet Gold-plated channel: -h (Wang et al) Very important to disentangle photon sources!

Build more precise theory framework for hard probes initial conditions Perturbative calculations at NLO Couple calculations to hydro Systematic analysis of final state effects

without too much theory bias

New ideas, improved models for jet-medium interactions.

0-10%

50-60%

PHENIX preliminary

In Plane

Out of Plane

L

Lajoie QM06

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Questions For The Next Few Years

What is the nature of parton energy loss? How strong are the different sources of photons and

dileptons? Constrain the temperature and time evolution of the fireball test for hydrodynamics.

How does the QCD medium react to jet energy loss? Dissipative? Collective?

Are there Mach cone effects? Can we learn about the speed of sound, the equation of state?

What are the transport properties of the quark gluon phase?

How far up in momentum are (non-perturbative) recombination effects important?

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Backup

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Challenges

Quark vs gluon energy loss:

Heavy quarks: Here: electrons from

charm and bottom

PHENIX

QCD DC 2006 10 Rainer Fries

Elliptic Flow v2

Finite impact parameter b > 0: Spatial anisotropy in the initial state Momentum anisotropy in the final state

Space momentum space translation

x

yz

Force P

Test EOSof the system

Test density/opacity of the medium LE

Bulk/soft particles Hard particles + Photons

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Length and energy scales

Coherence length

Transverse momentum accumulated through multiple scattering within the coherent regime

assume random walk average momentum transfer set by the medium

Define energy scale

2coh2cohcoh

2 ~

lNkT

LPM2coh E

l

LPM

coh EN

2LPM E

coh

2coh

Tkl

LPM: Landau, Pomeranchuk, Migdal

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Radiated Energy

• , : Incoherent regime

• , : LPM regime

• , : Coherent regime

LPME cohl

10Idzd

dI

cs NI

0

Ll cohLE LPM

2

2

LPM2

2

L

ELL

LPM0

2

0coh

0

11 EII

lI

dzd

dI

EL Ll coh LI

dzd

dI 10

LPME LPM suppression factor

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LPM Effect

Energy loss: integrate radiation spectrum

For E > L:

LPM effect; quadratic dependence on the medium

Additional medium independent contribution

For E < L:

LIIdz

dEL

2

0

2

0~

EEIdz

dELPM0

1~

2LE

EIE 0

Baier, Dokshitzer, Mueller, Peigne, Schiff, Zakharov

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The Ridge

Majumdar, Muller, Bass

Wiedemann et al