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Indications for the Onset of Deconfinement in Pb+Pb collisions at the SPS

Indications for the Onset of Deconfinement in Pb+Pb collisions at the SPS. P.Seyboth, MPI f ür Physik, München for the NA49 Collaboration. Introduction Search for structure in the energy dependence of Inclusive particle yields E-by-E fluctuations: K/ π , Q BE correlations

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Indications for the Onset of Deconfinement in Pb+Pb collisions at the SPS

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  1. Indications for the Onset of Deconfinement in Pb+Pb collisions at the SPS P.Seyboth, MPI für Physik, München for the NA49 Collaboration • Introduction • Search for structure in the energy dependence of • Inclusive particle yields • E-by-E fluctuations: K/π, Q • BE correlations • Anisotropic flow • Summary P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  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- and intermediate-mass dilepton enhancements • J/Ψ,Ψ’ yield suppression • Signatures not specific for deconfinement • Search for a threshold by varying the energy for the largest collision system (central Pb+Pb reactions) • SPS energy scan: 20,30,40,80,158 GeV/nucleon P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  4. Pb+Pb collision at 158A GeV P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  6. 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) constant βT ; π , d excluded from fit P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  7. early freezeout of multistrange hyperons ? P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  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 (assuming radially constant βT) P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  9. Rapidity spectra also: Ξ, Ω Extrapolation  4π yields (open dots from reflection at ycm= 0) P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  10. Rapidity spectra: energy dependence of width • width close to Landau • prediction for pions • better agreement with linear • increase with ybeam • clear mass hierarchy at SPS • (exclude p, Λ, Ξ containing • leading beam quarks) • 4π and mid-rapidity ratios • differ systematically P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  11. 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 • incease of γS= 0.5 → 0.8 • from p+p to A+A shows: • relaxation of canonical • suppression not enough ! ( NA49 data ) P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  12. 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  13. Energy dependence - π yields • increase of <π>/<NW> with energy gets steeper in the SPS range • π deficit changes to enhancement compared to p+p • pions are most abundant • produced 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  14. 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  15. Energy dependence of total yield of s,s quarks energy dependence of yields changes at 30A GeV sharp peak, then undersaturation of strangeness content P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  16. 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  17. 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  18. Energy dependence - average transverse mass NA49 preliminary Increase of <mT> for abundant final state particles ( π, K, p) slows sharply at the lowest SPS energy P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  19. More realistic model with initial QGP phase Y.Hama et al., Braz.J.Phys,34,322 (2004) • hydrodynamic evolution in QGP and hadronic phases (SPheRIO) • NeXus type initial conditions at t0 = 1 fm/c • (T0 = 135 → 265 MeV, ε0 = 1.4 → 11.4 GeV/fm3 at SPS) describes the rise of pion multiplicity and saturation of T* for Kaons P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  20. hypothetical trajectories in the phase diagram (Lattice-QCD phase boundary: Fodor,Katz JHEP04(2004)050) large (event-by-event) fluctuations are expected when the system hadronises close to the predicted critical point P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  21. 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  22. The Event-by-Event (p + 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  23. Smaller in a QGP than in a hadron gas (Jeon,Koch,Asakawa,Heinz,Müller) Effect of hadronisation ? Electric charge fluctuations ( C.Alt et al., nucl-ex/0406013 ) Central Pb+Pb collisions 158A GeV -0.6< y <2.4 Global charge conservation P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  24. 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  25. 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 from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  26. Anisotropic flow v2 Initial anisotropy ε in non-central collisions transformed into momentum anisotropy v2 by pressure at early reaction stage σ/σT ≈ 10 – 35 % ε = (<y2>+<x2>)/(<y2>-<x2>) RHIC SPS Smooth increase with collision energy towards hydrodynamic model prediction P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  27. Λ elliptic flow (preliminary) • event plane from pions • flattening of acceptance via • event plane shifting technique • correction for event plane • resolution • dE/dx identification of Λ decay • daughters • Λ signal/background 5 - 11 P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  28. v2(pT) at SPS and RHIC Λ increase of integrated v2 mainly due to increase of yield at large pT P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  29. Conclusion from the energy scan at the SPS • striking changes of energy dependence in 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 convincing anomalies in e-by-e fluctuations (K/π, charge), • BE correlations and flow • reaction scenario with onset of deconfinement at the SPS • provides a consistent explanation of the energy scan results • SPS energy range remains an interesting region for further study: • role of nuclear size (volume) in the onset of deconfinement • search for indications of the predicted critical point → Initiatives at the SPS, RHIC “fixed target”, CBM at GSI P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  30. The NA49 collaboration P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  31. blast-wave fit for a hadron resonance gas (procedure of B.Tomasik nucl-th/0304079) pions Kaons protons P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  32. energy dependence of Tf, βT Blast wave fit for a resonance gas of π, K, p : kinetic freezeout temperature Tf , flow velocity βT Tch P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  33. the energy dependence of the K/π ratios at midrapidity shows similar structure as the 4π results ! at midrapidity identification is from dE/dx and TOF P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  34. Excitation functions of 4πyields compared to model predictions P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  35. Multiplicity fluctuations at 158A GeV (preliminary) selected range: 4 < y < 5.5 small correction δ ≈ 10-2for fluctuation in proj. participants: (NA49 preliminary) width increases with energy ! maximum of fluctuations at Npart≈ 70 P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  36. dependence on acceptance : extrapolation to 4π : NA49 preliminary • fluctuations increase linearly with • acceptance p = <Nacc>/<N4π> • all charged >> negatives, positives no plausible explanation yet P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

  37. Fluctuations of <pT> vs system size at 158A GeV selected range: 4.0 < yπ< 5.5 corrected for limited 2-track resolution Similar centrality dependence as Nch fluctuations Correlation of <pT> with <Nch> due to energy conservation as in p+p ? (Mrowczynski,Rybczynski,Wlodarczyk nucl-th/040712) P.Seyboth: Indications for the Onset of Deconfinement from NA49 21st Workshop on Nuclear Dynamics, Breckenridge, 5-12 February 2005

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