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QCD thermodynamics with almost physical quark masses P é ter Petreczky

QCD thermodynamics with almost physical quark masses P é ter Petreczky Physics Department and RIKEN-BNL . Introduction : Lattice QCD and deconfinement at high temperature and density

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QCD thermodynamics with almost physical quark masses P é ter Petreczky

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  1. QCD thermodynamics with almost physical quark masses Péter Petreczky Physics Department and RIKEN-BNL • Introduction : Lattice QCD and deconfinement at high temperature and density • Chiral and deconfinement transition temperature in QCD • Equation of State at small quark masses • Nature of the deconfined phase at high temperatures, wQGP ? • Conclusions and Outlook WWND, February 12-17, 2007

  2. Improved lattice action for QCD thermodynamics Naïve (standard) discretisation : errors reduced discretization errors by finite difference scheme with next-to-nearest neighbor interaction Improved staggered action: p4fat3, asqtad, stout Algorithmic improvement : R-algorithm RHMC algorithm : x 20 speedup at small m

  3. Previous results on transition temperature and EoS 2-flavor QCD, Karsch, Laermann, Peikert, NPB (01) 605 Karsch, Laermann, Peikert, PLB 478 (00) 447

  4. Lattice calculations with p4fat3 action fat3 link improvement of flavor symmetry next-to-nearest neighbors (p4) rotational symmetry to RBC-Bielefeld collaboration : Ejiri,Karsch, Jung, P.P, Schmidt, Umeda (BNL) Cheng, Christ, Mawhiney (Columbia), Datta (Mumbai), Petrov (NBI) Doering, Van der Heide, Kaczmarek, Laermann, Miao (Bielefeld)

  5. Determining the transition temperature • 2+1 flavor QCD with physical strange quark mass and several • light quark masses : physical value • is varied by the lattice spacing ; • two sets of lattice spacing • Chiral condensate and Polyakov loop are order parameters • in for zero and infinite quark mass peak location defines the transition point • Use different volumes and Ferrenberg-Swedsen re-weighting to combine • information collected at different gauge couplings • Convert the pseudo-critical coupling to temperature • using scale determined from static quark potential

  6. 2.5% error band : 5 MeV 4% error band : 8 MeV • the peak position in and • is the same withing errors: • deconfinement and chiral transition • happen at the same temperature • no significant volume dependence of • the peak position • the finite volume behavior is • inconsistent with 1st ordre phase • transition

  7. Chiral and deconfinement transitions happen at one temperature

  8. Gray et al, PRD 72 (2006) 094507 Cheng et al, PRD 74 (2006) 054507

  9. Equation of State • New calculations : and lattices, pion mass of about • 200 MeV and along the line of constant physics ( LCP ) : • are varied in the way physical quantities, e.g. and

  10. Equation of State (cont’d) • rise in the entropy density is happens • at the transition temperature determined • from chiral condensate and Polyakov • loops • little cutoff dependence in the pressure • deviation from ideal gas limit is about • 10%

  11. Is 10% a large effect ? SU(3) gauge theory (2+1) flavor QCD Resummed perturbative calculations from : Blaizot, Iancu, Rebhan, hep-ph/0303185 Lattice data on pressure and entropy density at high temperatures can be described by re-summed perturbation theory

  12. Logarithms at work ! lattice calculations of the pressure in 3d effective theory, Schröder, hep-ph/0605057 Debye mass in lattice QCD perturbative treatment of hard modes: lattice data are parameterized as non-perturbative treatment of soft modes: both for quenched and full QCD quarks modify the perturbative pre-factors, non-perturbative effects are in the soft gluon sector Kaczmarek et al,D70 (2004) 074505; PRD 71 (05) 114510 SU(2) gluon dynamics Cucchieri et al, PRD 64 (2001) 036001

  13. Quark number susceptibility re-summed perturbative calculations from Blaizot, Iancu, Rebhan, hep-ph/0303185 vs. quenched continuum extrapolated lattice data from Gavai, Gupta, PRD 67 (03) 034501 Quark number susceptibilities are close to the ideal gas limit and can be described by re-summed perturbative calculations

  14. Summary and outlook • Deconfinement and chiral transition in finite temperature QCD happen • at the same temperature which is estimated to be : , • when expressed in units of the string tension : turns out to be compatible with previous estimates ( Karsch et al, NPB (01) 605 ) • Pressure, energy density and entropy density have be calculated at two lattice • spacing show a rapid rise at temperature • deviation from the ideal gas limit is about 10% for temperatures and • no significant cutoff dependence has been seen • Comparison with re-summed perturbation theory, effective 3d theory and additional • lattice data on quark number susceptibility and the Debye mass suggest that • we have wQGP for • To get cutoff effects completely under control calculations on are needed • Such calculations are being done by HotQCD collaborations ( 8 institutions ) using • p4fat3 and asqtad actions on 10% of 360Tflop BG/L @ LLNL, stay tuned !

  15. Backup slides :

  16. Aoki et at, JHEP 0601 (2006) 089 (impr. flavor symmetry only)

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