precision probes for hot qcd matter rainer fries texas a&m university & riken bnl qcd...
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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
QCD DC 2006 3 Rainer Fries
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
QCD DC 2006 4 Rainer Fries
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
QCD DC 2006 5 Rainer Fries
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
QCD DC 2006 6 Rainer Fries
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
QCD DC 2006 7 Rainer Fries
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?
QCD DC 2006 9 Rainer Fries
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
QCD DC 2006 11 Rainer Fries
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
QCD DC 2006 12 Rainer Fries
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
QCD DC 2006 13 Rainer Fries
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