Constraints for the transport coefficients of the QGP

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Constraints for the transport coefficients of
the QGP Roy A. Lacey Chemistry Dept. Stony Brook
University

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t
Thermalized partonic Fluid! (s)QGP?
What are the transport properties of this fluid?
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Probes for estimating transport coefficients
Jet Quenching
Flow
Primary Control Parameters
Flow and jet suppression measurements are
important probes
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Jet Suppression
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Lesson Fits with detailed error bars are of very
little value if we cannot constrain
the correct model ingredients

• Issues
• Collision Energy loss?
• Radiative Energy loss?
• Model implementation details
• Role of expansion dynamics
• etc.

New model constraints are required
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Path length constraint for jet quenching

• A fixed centrality
• Constrains energy density for an average geometry
• Reaction plane dependence
• Varies effective path length of parton through
  medium for a given energy density
• Path length dependence of energy loss is an
  important constraint

Scaling provides an important mechanistic
constraint !
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RAA relative to the reaction plane
BBC/MPC

• Sizeable difference between out-of-plane and
  in-plane RAA for a broad range of pT
• This difference is effectively v2

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High-pT (anisotropy) v2

• Sizeable v2 observed at high pT, not due to flow
• Relatively flat dependence reflects path length

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A Scaling constraint for RAA
Idea!
Beer Lamberts law
Straightforward validation scaling tests!
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Geometry
A
B

• Estimate for L

• Geometric fluctuations are very important
• be skeptical of
  any claim that does not include them

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Scaling of Jet Quenching
Scaling validated!
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Scaling of Jet Quenching
Similar scaling found For different
collision systems.
Profound Value ? global simplification ? Focus
on essential variables
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Jet Quenching Rxn dependence
From slope
Further validation of path length scaling Very
important ? no new information
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Medium Response Transport Coefficients
QCD Sonic Boom
Gives sound speed directly Sets upper limit on
viscosity.
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QCD Sonic Boom?
Data
Total 3PC jet correlations
Data compatible with the presence of a Mach Cone
away-side jet ? important upper limit for ?/s
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?/s estimates

• Issues
• Data (role of non-flow?)
• pre vs post hadronic
• contributions
• Extraction procedure
• Initial conditions (e)
• Fit constraints
• Species dependence
• etc

Uncertainty in critical path items is common to
all methodologies
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New RXN detector
Non-flow contributions?
BBC/MPC
Event planes
Excellent agreement between measurements
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Overall Scaling of Elliptic Flow at RHIC
Chaudhuri
Viscosity required for scaling ? Limit ?
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Universal Scaling - Quarks
Vn is universal
Gives quark flow and an estimate of ?/s
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Is flow hadronic or partonic?
?/s from hadronic phase is very large
10-12x(1/4p) No room for such values!
Partonic flow dominates!
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Hadronic flow at lower energies
PRL 85, 940 (2000)
PRL 85, 940 (2000)
Hadronic flow depend on particle species
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Hydrodynamic Model Comparison
h/s 0
h/s 1/4p
h/s 2 x 1/4p
h/s 3 x 1/4p
Initial conditions?
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Hybrid Approach
Operational Ansatz (Ollitrault Gombeaud)
The Boltzmann equation reduces to hydrodynamics
when the mean free path is small
C. Marle, Annales Poincare Phys.Theor. 10,67
(1969).
Two extremes
(re-scattering) Hydrodynamic flow
(no re-scattering) No flow development
eccentricity
Mean transverses size
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Knudsen number parameterization
Strategy quantify the viscous corrections to
hydrodynamics via a simple fitting procedure, to
obtain K as a function of Npart
Experimental constraint
Geometry (from model)
Ideal hydrodynamics
Lattice EOS
Obtain from fits to data (viscous correction)
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Calibration of the method
Methodology successfully proofed very important
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Viscosity estimates at AGS - SPS
Ivanov et al
Significant deviations From hydrodynamic calculat
ions
From fits
Further study of hadronic viscosity underway
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Summary

The fluid which leads to large collective flow is
also responsible for strong jet quenching