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Quark Matter 2006 November 18, 2006

Quark Matter 2006 November 18, 2006 Klaus Reygers University of Münster Germany for the WA98 collaboration. Hadron Suppression and Nuclear k T Enhancement Studied with Neutral Pions from p+C, p+Pb, and Pb+Pb Collisions at  s NN = 17.3 GeV. The question is ….

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Quark Matter 2006 November 18, 2006

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  1. Quark Matter 2006 November 18, 2006 Klaus ReygersUniversity of MünsterGermanyfor the WA98 collaboration Hadron Suppression and Nuclear kT Enhancement Studied with Neutral Pions from p+C, p+Pb, and Pb+Pb Collisions at sNN = 17.3 GeV

  2. The question is … • Strong evidence for QGP formation • Characterization of the medium(dNgluon/dy 1500) High-pT-hadron suppression at RHIC What can we say at CERN SPS energies? 2 Klaus Reygers, Quark Matter 2006

  3. Is there Jet Quenching at sNN = 17.3 GeV?We don’t know! p+W @ s = 19.4GeV Parameterizationfrom Blattnig et al:Large uncertainty! Blattnig et al.,Phys. Rev. D 62 (2000) 094030 Parton energy lossdNgluon/dy = 400 – 600 D. d’Enterria, Phys. Lett. B 596 (2004), 32 C. Blume, nucl-ex/0609022 • No measured p+p reference at same energy • Nuclear kT enhancement not well understood at sNN ~ 17 GeV 3 Klaus Reygers, Quark Matter 2006

  4. Cronin enhancement: Slightly larger in A+A than in p+A Strongly model dependent: Maximum enhancement factors between ~2 and ~4 Cronin Enhancement at sNN = 17.3 GeV Calculation without parton energy loss: sNN = 17 GeV Cronin + shadowing I. Vitev, M. Gyulassy, PRL 89, 252301,2002 Barnaföldi et al., nucl-th/0307062 I. Vitev, M. Gyulassy X.N. Wang, PRC 61, 064910, 2000 Expect to take out effect of Cronin enhancement on RAAto large extent with p+Pb reference 4 Klaus Reygers, Quark Matter 2006

  5. Idea of this Analysis:p+C and p+Pb as Reference for Pb+Pb RAA p0 spectra published: Eur.Phys.J.C23:225-236,2002 Presented in this talk p + C: →Replacement for p+p reference (Ncoll  1.7  expect small Cronin enhancement) p + Pb: →Study nuclear kT enhancement by comparing to p+C → Reference for RAA in Pb+Pb: partially removes effect of Cronin enhancement 5 Klaus Reygers, Quark Matter 2006

  6. WA98 Experiment 2.1 < h < 3.0 High Energy Photon Trigger(pT,g > ~ 0.7 GeV/c) 3.5 < h < 5.5 Minimum bias trigger 6 Klaus Reygers, Quark Matter 2006

  7. Same calibration as in Pb+Pb run Confirmed with comparison to GEANT simulation Calibration and Peak Extraction p+C p+C p0 peak position in GEANT simulation p0 peak width in GEANT simulation 7 Klaus Reygers, Quark Matter 2006

  8. p0 Spectra in p+C and p+Pb • Transition to high-pT photon sample at pT = 1.4 GeV/c • Similar pT reach as in Pb+Pb p0 in sNN = 17.3 GeV p+A preliminary 8 Klaus Reygers, Quark Matter 2006

  9. Cross Check: Comparison to NA49 Ratio: WA98 / NA49 sNN = 17.3 GeV p+C preliminary NA49, hep-ex/0606028 Good agreement with charged pions from NA49 9 Klaus Reygers, Quark Matter 2006

  10. RpPb with p+C Reference • RpPb consistent with 1 at high pT • Hint of Cronin enhancement p+C reference Effect of minimum biastrigger threshold taken into account preliminary 10 Klaus Reygers, Quark Matter 2006

  11. No indication of Cronin enhancement in p+C from comparison to NA49 p+p Agreement with Blattnig parameterization within errors p+C as p+p Reference NA49, Eur. Phys. J. C 45, 343 (2006) preliminary preliminary 11 Klaus Reygers, Quark Matter 2006

  12. RAA in central Pb+Pb at sNN = 17.3 GeV Proton-nucleus reference measured at same energy: 0-12.7% most central Pb+Pb p0 nuclear overlap function preliminary p+C reference 0-12.7% most central Pb+Pb p0 suppression with respect to p+Pb reference in central Pb+Pb (RAA ~ 0.7 for 0 − 12.7%) p0 preliminary p+Pb reference 12 Klaus Reygers, Quark Matter 2006

  13. RAA in Pb+Pb with p+C Reference:Centrality Dependence Ncoll,Pb+Pb = 712 ± 71 Ncoll,Pb+Pb = 569 ± 57 Ncoll,Pb+Pb = 408 ± 41 Ncoll,Pb+Pb = 807 ± 81 Ncoll,Pb+Pb = 207 ± 21 preliminary Ncoll,Pb+Pb = 78 ± 12 p0RAA ~ 0.4 in 1% most central Pb+Pb collisions (p+C reference) 13 Klaus Reygers, Quark Matter 2006

  14. RAA in Pb+Pb with p+Pb Reference:Centrality Dependence Ncoll,Pb+Pb = 807 ± 81 Ncoll,Pb+Pb = 712 ± 71 Ncoll,Pb+Pb = 569 ± 57 Ncoll,Pb+Pb = 408 ± 41 Ncoll,Pb+Pb = 207 ± 21 preliminary Ncoll,Pb+Pb = 78 ± 12 p0RAA ~ 0.4 in 1% most central Pb+Pb collisions (p+Pb reference) 14 Klaus Reygers, Quark Matter 2006

  15. p0 Suppression in Central Pb+Pb preliminary p0 in Pb+Pb at sNN = 17.3 GeV p0 suppression in Pb+Pb at sNN = 17.3 GeV for Npart > ~300 15 Klaus Reygers, Quark Matter 2006

  16. Summary 1% most central:Ncoll,Pb+Pb = 807 ± 81 preliminary • p0’s from sNN = 17.3 GeV p+C and p+Pb used as reference for RAA • p0 suppression at high pTin central Pb+Pb • Looking forward to extraction of dN/dygluon 16 Klaus Reygers, Quark Matter 2006

  17. Backup slides 17 Klaus Reygers, Quark Matter 2006

  18. Comparison to other RpA’s 18 Klaus Reygers, Quark Matter 2006

  19. Comparison to WA80 19 Klaus Reygers, Quark Matter 2006

  20. Cronin Enhancement: Up to a factor 2 for A 200 Large differences between models! Cronin Enhancement in p+A at sNN = 17.3 GeV Models calculations for p+A at sNN = 17.3 GeV: Rp+A pT (GeV/c) Barnaföldi et al., nucl-th/0307062 20 Klaus Reygers, Quark Matter 2006

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