Properties%20of%20the%20sQGP%20at%20RHIC%20and%20LHC%20energies

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Properties of the sQGP at RHIC and LHC energies
Wolfgang Cassing CERN, 04.06.2007
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Aim Transport study of relativistic many-body
systems
Transport theory off-shell Kadanoff-Baym
equations for the Green-functions Glth(x,p) in
phase-space representation
Actual solutions Monte Carlo simulations with a
large number of test-particles
Parton-Hadron-String-Dynamics (PHSD)
Scetch of an ultrarelativistic nucleus-nucleus
collision (S. A. Bass)
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what are the properties of the new medium?
At RHIC the strong QGP (sQGP) was found, but
Ask lattice QCD ? effective approach!
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From lattice QCD to gluon quasiparticle properties
quasiparticle entropy
entropy
mass
we-3p
width
mass
coupling
width
spectral function
Andre Peshier, PRD 70 (2004) 034016
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Gluonic quasiparticles of the sQGP
T 1.053 Tc
T 1.35 Tc
T 3 Tc
? broad distributions in (w,k)
Andre Peshier, PRD 70 (2004) 034016
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average glue-glue cross section
percolation parameter
plasma parameter
shear viscosity
gt The QGP looks like an almost perfect liquid !
PRL 94 (2005) 172301
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The Dynamical QuasiParticle Model (DQPM)
The quasiparticle entropy density
gluons
quarks
antiquarks
Complex selfenergies, e.g.
some thermodynamics
? pressure P
energy density
interaction measure
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The DQPM model assumptions
Spectral functions for partonic degrees of
freedom (g, q, qbar)
gluon mass
quark mass
gluon width
quark width
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The strong coupling g2
3 parameters Ts/Tc0.46 c28.8 l2.42
? Quasiparticle properties (Nf3 Tc 0.185 GeV)
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DQPM thermodynamics (Nf3)
some short-hand notations
time-like - space-like
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Time-like and space-like quantities
Example
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Time-like and space-like densities
densities
scalar densities
? time-like densities are small except close to
Tc !
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Time-like and space-like energy densities

• space-like energy densities dominate except
  close to Tc !
• space-like parts are identified with potential
  energy densities!

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Thermodynamical consistency ?
Total energy density
gt matches well the thermodynamical energy
density!
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Potential energy per time-like parton
Potential energy
Plasma parameters
liquid
huge !
gas
? Partonic liquid should persist at LHC !
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Potential energy versus parton density
Potential energy
Parton density
Gluon fraction
? PHSD
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Self-energies of time-like partons
gluons
quarks
? PHSD
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Effective 2-body interactions of time-like partons
2nd derivatives of interaction densities
? PHSD
effective interactions turn strongly attractive
below 2.2 fm-3 !
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Finite quark chemical potentials
energy density
parton density
pot. energy per particle
pressure

• slight increase with chemical potential
  close to Tc
• Fermion potential energy per particle practically
  independent !

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Parton densities and gluon fraction

• fermion densities increase with quark chemical
  potential
• gluon densities slightly decrease !

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Parton energy densities

• increase with chemical potential close to
  Tc
• gluon potential energy density practically
  independent !

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Net fermion densities
Net fermion densities approximately scale with T2
and chemical potential mq !
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Net fermion density comparison to lQCD
Nf2 lQCD C. R. Allton et al., PRD 68
(2003) 014507
Comparison to lQCD looks quite reasonable !
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Dilepton back-to-back radiation from the sQGP
Born rate
DQPM rate
Nf2 lQCD F. Karsch et al., PLB 530
(2002) 147
? massive suppression of low mass dileptons
in line with lQCD !
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Dilepton radiation from the sQGP NA60
Preliminary PHSD results
NA60 data
sQGP is here!
Conjecture the sQGP shows up already at SPS
energies !
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Summary

• The dynamical quasiparticle model (DQPM) well
  matches lQCD (with only 3 parameters) !
• DQPM allows to extrapolate to finite quark
  chemical potentials presently out of reach for
  lQCD.
• DQPM separates lime-like quantities from
  space-like (interaction) regions (needed for
  off-shell transport).
• DQPM provides mean-fields for gluons and quarks
  as well as effective 2-body interactions ? PHSD
• and gives transition rates for the formation of
  hadrons if the average distance is larger than
  0.77 fm ? PHSD .
• The plasma parameter G suggests that the sQGP
  and its related experimental observations
  (scaling of elliptic flow with parton number
  etc.) will persist at LHC (i.e. the partonic
  liquid).

• PHSD Conjecture the sQGP shows up already at
  SPS energies !

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Dilepton radiation from the sQGP NA60