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Indications for the Onset of Deconfinement in Pb+Pb Collisions at the CERN SPS from NA49

Indications for the Onset of Deconfinement in Pb+Pb Collisions at the CERN SPS from NA49. Introduction Search for structure in the energy dependence of Inclusive particle production E-by-E fluctuations, BE correlations, flow Summary and conclusion. P.Seyboth, MPI f ü r Physik, Munich

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Indications for the Onset of Deconfinement in Pb+Pb Collisions at the CERN SPS from NA49

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  1. Indications for the Onset of Deconfinement in Pb+Pb Collisions at the CERN SPS from NA49 • Introduction • Search for structure in the energy dependence of • Inclusive particle production • E-by-E fluctuations, BE correlations, flow • Summary and conclusion P.Seyboth, MPI für Physik, Munich for the NA49 collaboration P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  2. Introduction: Pb+Pb collisions at top SPS energy • Initial energy density exceeds the critical value predicted by lattice QCD( 1 GeV / fm3 ) • Strong collective behavior • anisotropic and radial flow • transverse expansion of the matter droplet by factor 2 • Proposed signatures for deconfinement observed • Strangeness enhancement • Low-mass dilepton enhancement • J/Ψ,Ψ’ yield suppression • Signatures not unique • Search for a threshold by varying the energy for the largest collision system (central Pb+Pb reactions) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  3. 2,5 < p < 10 GeV : TOF + dE/dx at midrapidity p > 7 GeV dE/dx forward rapidity The NA49 Detector Target: 20cm liquid H2 or Pb foil VCAL detects projectile spectators Δp/p2 = 7 (0.3) • 10-4 (GeV/c)-1 (VTPC-1, VTPC+MTPC) dE/dx resolution 3 – 6 % TOF resolution ~ 60 ps P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  4. Pb+Pb collision at 158A GeV P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  5. NA49 energy scan program of central Pb+Pb collisions search for structure in the energy dependence of observables which may be linked to the onset of deconfinement PRC 66(2003) 054902 preliminary P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  6. Rapidity spectra also: Ξ, Ω Extrapolation  4π yields (open dots from reflection at ycm= 0) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  7. Transverse mass spectra at mid-rapidity 158A GeV many spectra measured well described by fireball model assuming common temperature and flow “blast wave”: (Schnedermann,Sollfrank, Heinz : PRC 48 (1993) 2462) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  8. Transverse mass spectra at lower energy: “blast wave” model describes spectra at all SPS energies 40A GeV 30A GeV 20A GeV “kinetic” freeze out at T  120 –130 MeV, βT 0.4 – 0.5 at SPS P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  9. Particle yields – statistical model (fits by F.Becattini et al, PRC69(2004)024905) • hadron species populated • according to phase space • probabilities (max.entropy) • (Fermi,Hagedorn) • strangeness sector not fully • saturated (Rafelski) • statistical model successful, • T, μB, γS, V • larger value of γS in A+A • due to relaxation of local • strangeness conservation P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  10. Particle yields at 40A, 80A GeV – statistical model at lower energies μB increases, while T decreases slightly P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  11. Global view - Phase diagram • statistical model describes yields • from SIS to RHIC energy • T of “hadrochemical” freeze out • increases SIS  RHIC • μB decreases (increase of pion • production) • freeze out at E  1 GeV per particle •  dashed line QGP 1st order Hadrons (Cleymans and Redlich, PRL 81(1998) 5284 ) (Lattice-QCD phase boundary: Fodor,Katz JHEP04(2004)050) hadrochemical freeze out parameters approach the phase boundary at SPS P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  12. Energy dependence - π yields • increase of <π>/<NW> with energy gets steeper in SPS range • π deficit changes to enhancement compared to p+p • pions are most abundant • particle species •  measure of entropy • in statistical models SMES: statistical model of the early stage (Gazdzicki,Gorenstein : Acta Phys.Pol. B30(1999)2705) Increase of initial d.o.f . g between AGS and SPS ? P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  13. Energy dependence - ratio of K ,Λ yields to pions • sharp peak of • K+/π+ ratio • smooth rise of • anti-Λ/π • ( s quarks) hadronic models do not (yet ?) reproduce the sharp peak • similar peak in • Λ/π ratio • structure in K–/π– • ( s quarks) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  14. Energy dependence – ratio of strange hadrons to pions strangeness to pion ratio peaks sharply at the SPS mixed SMES explanation: - entropy, number of s,sbar quarks conserved from QGP to freezeout - ratio of strange/nonstrange d.o.f. rises rapidly with T in hadron gas - Es drops to predicted constant level above the deconfinement threshold partonic mixed partonic hadronic hadronic onset of deconfinement at SPS ? P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  15. Energy dependence – inverse slope parameters • inverse slope parameter T of K+ and K- constant at SPS • approximately constant pressure and temperature • in mixed phase ? (L.van Hove, PLB89(1982)253 M.Gorenstein et al.,PLB567(2003)175) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  16. Energy dependence - average transverse mass Increase of <mT> for abundantly produced particles ( π, K, p) slows sharply at the lowest SPS energy P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  17. The Event-by-Event K/π ratio max.likelihood fit for each event σ2dyn = σ2data – σ2mixed Increased fluctuation signal at lower beam energies Beam Energy NA49 preliminary P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  18. The Event-by-Event p/π ratio Beam Energy NA49 preliminary The distribution of the E-by-E p/π ratio is narrower for data than mixed events. Effect of baryon resonance decay ? P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  19. Smaller in a QGP than in a hadron gas (Jeon,Koch,Asakawa,Heinz,Müller) Effect of hadronisation ? Electric charge fluctuations Central Pb+Pb collisions 158A GeV Global charge conservation P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  20. Remove effect of global charge conservation : No clear energy dependence of charge fluctuations at SPS QGP signature possibly masked by effect of resonance decays P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  21. BE correlations: energy dependence of radius parameters kT ~ 0.15 GeV/c Rlong increases slowly Rside constant Rout constant no evidence of anomalies or “soft point” of EOS P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  22. Anisotropic flow v2 Initial anisotropy ε in non-central collisions transformed into momentum anisotropy v2 by pressure at early reaction stage ε = (<y2>+<x2>)/(<y2>-<x2>) RHIC SPS Smooth increase with collision energy towards hydrodynamic model prediction P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  23. Conclusion from the energy scan at the SPS • structure observed at low SPS energy in central Pb+Pb collisions • the rate of increase of pion production steepens • the strange particle to pion ratio peaks sharply • constancy of the slope of π and K mT- spectra • no evident anomalies in e-by-e fluctuations (K/π, charge), • BE correlations and flow • present models without deconfinement in the early phase do not • reproduce details of energy dependence • reaction scenario with onset of deconfinement at the SPS can • explain the observed structure • plan to continue SPS program with lighter nuclei: • role of the initial volume in the onset of deconfinement • search for the predicted critical point P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  24. The NA49 collaboration P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  25. Extra slides for discussion P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  26. Estimate of initial energy density at 158A GeV • from projectile energy loss and interaction volume: • from transverse energy production and Bjorken’s model: NA49, PRL 75 (1995) 3814 initial energy density ε > εc 1 GeV/fm3 P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  27. Λ , Ξ and Ω rapidity spectra P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  28. Transverse mass spectra in p+p collisons at 158 GeV “blast wave” model fit consistent with small βT consistent with common temperature T  145 MeV P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  29. Statistical model for p+p collisions at 158 GeV P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  30. Energy dependence of K , Λ yields • carriers of s quarks • carriers of s quarks P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  31. Energy dependence of total yield of s, s carriers • carriers of s quarks • carriers of s quarks P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  32. P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  33. System size dependence of strangeness production at 158A GeV disappearance of canonical suppression for Npart > 60 P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  34. P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  35. P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  36. Balance function for oppositely charged particles 158A GeV similar narrowing at SPS and RHIC (NA49 preliminary) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  37. Event-by-Event estimation of the particle ratios Event Ensemble: One Event: <dE/dx> <dE/dx> • Vary relative normalization of the particle species (K/p,p/p) in the probability density function • Extract ratios with maximum likelihood fit log(Ptot [GeV]) log(Ptot [GeV]) Fit dE/dx spectra in 4D binning <dE/dx> Probability density function: <dE/dx> log(Ptot [GeV]) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  38. v2(pT) at SPS and RHIC P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  39. Fluctuations of <pT> vs system size at 158A GeV selected range: 4.0 < yπ< 5.5 corrected for limited 2-track resolution P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  40. Fluctuations of <n-> vs system size at 158A GeV selected range: 4 < y < 5.5 correction for fluct. in projectile participants: (NA49 preliminary) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

  41. Multiplicity fluctuations at 158A GeV (NA49 preliminary) P.Seyboth: Indications for the onset of deconfinement in Pb+Pb collisions at the CERN SPS from NA49 (ISMD2004)

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