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Properties of the sQGP at RHIC and LHC energies

Properties of the sQGP at RHIC and LHC energies. Wolfgang Cassing CERN, 04.06.2007. Aim: Transport study of relativistic many-body systems. Transport theory : off-shell Kadanoff-Baym equations for the Green-functions G < h (x,p) in phase-space representation. Actual solutions:

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Properties of the sQGP at RHIC and LHC energies

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  1. Properties of the sQGP at RHIC and LHC energies Wolfgang Cassing CERN, 04.06.2007

  2. Aim:Transport study of relativistic many-body systems Transport theory: off-shell Kadanoff-Baym equations for the Green-functions G<h(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)

  3. At RHIC the strong QGP (sQGP) was found, but what are the properties of the new medium? Ask lattice QCD  effective approach!

  4. From lattice QCD to gluon quasiparticle properties quasiparticle entropy: entropy mass: w=e-3p width: mass coupling: width spectral function: Andre Peshier, PRD 70 (2004) 034016

  5. 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

  6. average glue-glue cross section: percolation parameter: plasma parameter: shear viscosity: => The QGP looks like an almost perfect liquid ! PRL 94 (2005) 172301

  7. The Dynamical QuasiParticle Model (DQPM) The quasiparticle entropy density: gluons quarks antiquarks Complex selfenergies, e.g. : + some thermodynamics:  pressure P energy density: interaction measure:

  8. The DQPM model assumptions Spectral functions for partonic degrees of freedom(g, q, qbar): gluon mass: quark mass: gluon width: quark width:

  9. The strong coupling g2 3 parameters:Ts/Tc=0.46; c=28.8; l=2.42  Quasiparticle properties (Nf=3; Tc = 0.185 GeV)

  10. DQPM thermodynamics (Nf=3) some short-hand notations: +: time-like -: space-like

  11. Time-like and space-like quantities Example:

  12. Time-like and space-like densities ‚densities‘: scalar densities:  time-like densities are small except close to Tc !

  13. 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!

  14. Thermodynamical consistency ? Total energy density: => matches well the thermodynamical energy density!

  15. Potential energy per time-like parton Potential energy: Plasma parameters: liquid huge ! gas  Partonic liquid should persist at LHC !

  16. Potential energy versus parton density Potential energy: Parton density: Gluon fraction:  PHSD

  17. Self-energies of time-like partons gluons quarks  PHSD

  18. Effective 2-body interactions of time-like partons 2nd derivatives of interaction densities  PHSD effective interactions turn strongly attractive below 2.2 fm-3 !

  19. 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 !

  20. Parton densities and gluon fraction • fermion densities increase with quark chemical potential • gluon densities slightly decrease !

  21. Parton energy densities • increase with chemical potential close to Tc ; gluon potential energy density practically independent !

  22. Net fermion densities Net fermion densities approximately scale with T2 and chemical potential mq !

  23. Net fermion density – comparison to lQCD Nf=2; lQCD: C. R. Allton et al., PRD 68 (2003) 014507 Comparison to lQCD : looks quite reasonable !

  24. Dilepton ‚back-to-back‘ radiation from the sQGP Born rate: DQPM rate: Nf=2; lQCD: F. Karsch et al., PLB 530 (2002) 147  massive suppression of low mass dileptons in line with lQCD !

  25. Dilepton radiation from the sQGP – NA60 Preliminary PHSD results: NA60 data sQGP is here! Conjecture: the sQGP shows up already at SPS energies !

  26. 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 !

  27. Dilepton radiation from the sQGP – NA60

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