2. Gabor David QM01 Miklos Gyulassy (Collegium Budapest/Columbia U) Adapted from Axel Drees, X.N. Wang, W.Zajc, and G. David Talks at QM2001 First Hints for Jet Quenching at RHIC l Introduction l p-p and p-A collisions l CERN high pT results l First data from RHIC l Status * Hard vs Soft QCD * Cronin Enhancement * WA98 No Quench? * Incredible!!

3. Bibliography 1.Quark Matter 2001, SUNY Stony Brook, Jan. 15-20, 2001 all talks at ftp://woodstock.physics.sunysb.edu/pub/ftp://woodstock.physics.sunysb.edu/pub/ 2.X.~Wang and M.~Gyulassy, ``Energy and centrality dependence of rapidity densities at RHIC,'' nucl-th/0008014. 3. M.~Gyulassy, I.~Vitev and X.~N.~Wang, ``High $p_T$ azimuthal asymmetry in non-central $A + A$ at RHIC,'' nucl-th/0012092. 4. P.~Levai, G.~Papp, G.~Fai and M.~Gyulassy, ``Kaon and pion ratio probes of jet quenching in nuclear collisions,'' nucl-th/0012017. 5 M.~Gyulassy, P.~Levai and I.~Vitev, ``Non-Abelian energy loss at finite opacity,'' Phys.\ Rev.\ Lett.\ {\bf 85}, 5535 (2000), [nucl-th/0005032]; Nucl.\ Phys.\ {\bf B594}, 371 (2001) [nucl-th/0006010] 6. X.~Wang and M.~Gyulassy, ``Gluon shadowing and jet quenching in A + A collisions at s**(1/2) = 200-GeV,'' Phys.\ Rev.\ Lett.\ {\bf 68}, 1480 (1992); Phys.Rev.D45:844-856,1992, Phys.Rev.D44:3501-3516,1991

4. Hard vs Soft QCD Dynamics l Slow Onset of (semi)hard processes (XNWang & Hwa’89) (Eskola, Landshoff, Lindfors, Kajantie’89) … HIJING, VNI, NEXUS XNWang QM01 1)pQCD Resolved Hard Processes 2)Soft (Regge) Phenomenology (XNWang &MG ’91)

5. Energy dependence of dN/dy in pp HIJING, NEXUS: Soft  Strings dN/dy » Const. AA Collisions XNWang QM01

6. First Hints of Mini-Jet Showers in dN/d  at RHIC soft physics with quenching No jet quenching STAR PHENIX BRAHMS X.N. Wang, MG ‘00 PRL85(00)3100

7. First Global Hint of Extreme Dense Gluon Plasma ? dN/d  /.5N part N part Centrality Dependence of dN ch /d  P. Steinberg QM01 dN gluon /d y  HIJING ” r glue (t 0 =0.1 fm/c) » 10/fm 3 dN gluon /d y  EKRT ” r glue (t 0 =0.1 fm/c) » 50/fm 3 XNW,MG nucl-th/0008014 nucl-ex/0012008

8. dE T /d h dN ch /d h b Initial Geometry E ZDC N BBC Experimental Handles Determining Collision Impact Parameter and N(participants)

9. 0-5% 5-10% 10-15% 15-20% PHENIX preliminary Use combination of cuts on l Zero Degree Calorim. and Beam-Beam Counters or dNch/d h or dET/d h to define centrality classes l Glauber (Eikonal) geometry modeling ETET ETET E ZDC N BBC b PHENIX Centrality Cuts

10. Phenix Centrality Selection W.Zajc QM01

11. l Data available over wide range of  s=20-2000 GeV, but not for 130 GeV ! l Good power law fit: d 2 N/dp t 2 = A (p 0 +p t ) -n Well Known Inclusive p t -Distributions in p-p A.Dress QM01

12. l Hard pQCD Probes: l Drell-Yan Heavy Quarks (D, Y) Direct g l Jets, high pT hadrons Hard Probes In Heavy Ion Collisions Z  Observables 1.dE/dx in QGP  jet quenching 2.Deconfinement  J/  suppression beams of hard probes: jets, J/  …. Vacuum QGP

13. Drell-Yan and Y Production at CERN/SPS C. Lourenco NA50 QM01 Suppressed even in p+A !!

14. Results from the SPS l data well described by pQCD + (intrinsic + initial) k T (A,Q) broadenning l data equally well described by hydrodynamic fit A. Dress QM01 However, No Rutherford Power Law Tail

15. Extrapolating from pp to AA l hard scattering processes scale with binary collisions: l scale to min. bias Au-Au: l scaling to central collisions: pp min. bias 5% central Glauber Eikonal Geometry }

16. The Cronin Effect l modification of p t spectrum in p-A collisions : A

17. Comparing CERN-SPS Pb-Pb to p-p R AA exhibits amplified Cronin Enhancement at SPS energies R AA » (R pA ) 2 Parton energy loss, if any, is overwhelmed by initial state soft multiple collisions at SPS! X.N.Wang AA 4 N part /2N bin * dE/dx is small at SPS due to short plasma lifetime and low gluon density MG, P. Levai, I. Vitev, PRL85(00)5535

18. l first high p t data from RHIC: l p t range to 6 GeV, covering >6 orders of magnitude l well above what was reached at the SPS Inclusive p t Spectra of charged Particles J.C. Dunlop, STAR F. Messer, PHENIX A.Dress QM01

19. G. David, PHENIX F. Messer, PHENIX J.Velkovska, PHENIX l  0 from 1 to 4 GeV l good agreement with h - below 2 GeV l agreement in shape with   from 0.3 to 2.2 GeV Preliminary PHENIX Inclusive p t Spectra of Pions and h ± Puzzle: What flavor Hadrons survive At high pT?

20. Preliminary PHENIX Hint that pbar > p - ??? l Spectacular Quench of Pions l Why do baryons survive? l Baryonium Matter p T > 2 GeV? F. Messer, PHENIX J.Velkovska, PHENIX H.Ohnishi, PHENIX ?? A. Dress QM01

21. Preliminary Centrality Dependence of pt Spectra F. Messer, PHENIX A. Dress QM01 G.David, PHENIX l Centrality dependence: l complete systematics for charged central and peripheral for    l Comparison to p-p l central collisions below p-p extrapolation l peripheral agree reasonably with p-p extrapolation (**note systematic uncertainty ~60% due to N coll )

22. Preliminary Quenching Pattern in central Au-Au l Use identical p-p parameterization for all data sets l normalize data to number of binary collisions l divide by p-p parameterization UA1(130)/42 mb l Characteristic features: l increases up to ~ 2 GeV l saturates at R AA < 1 l decrease at high p t l Issues: large systematic error ~ 30% l data: normalization, differences in shape, centrality selection, flavor.. l systematic uncertainty of p-p parameterization A. Dress QM01

23. Ratio Central/Peripheral l normalize central and peripheral to number of collisions l different systematic errors: l many experimental errors cancel l systematic uncertainty ~60% on N coll within systematic errors: R AA < 1

24. Comparison with pQCD P.Levai, G. Fai, G. Papp, MG (QM01) Peripheral Collisions Follow simple pQCD Central Collisions Require Medium Dependent pQCD Very High Gluon Plasma Opacity L/ l » 4 D E GLV /E glue » 0.4

25. P.Levai, G. Fai, G. Papp, MG (QM01) Cronin Enhancement vs Jet Quenching Cronin Enhancement dE GLV /dx Quench

26. Comparison with QCD calculations I l excellent agreement with pQCD calculation in Peripheral Collisions for charged particles and for identified   Peripheral Au-Au collisions N part ~ 5±3

27. Comparison with QCD Calculations II l p-QCD over estimates the cross-section for  0 at least a factor of 5 l for charged factor of 2 (calculation does not describe p &  p contribution) l shadowing and p t -broadening seem insufficient l calculation including constant energy loss consistent with  0 l for charged magnitude & shape different in detail central Au-Au collisions

28. Azimuthal Asymmetries in Non-Central Collisions Almond shape overlap region in coordinate space Momentum space P. Jacobs and G. Cooper, nucl- ex/0008015 Raimond Snellings QM01

29. A Hydro Calculation of Elliptic Flow P. Kolb, J. Sollfrank, and U. Heinz Equal energy density lines Raimond Snellings QM01

30. A Hydro view of the world l Hydro calculations: P. Huovinen, P. Kolb and U. Heinz Raimond Snellings QM01

31. Preliminary STAR charged particle anisotropy p t < 4.5 GeV/c vs Hydrodynamcs l Only statistical errors l Systematic error 10% - 20% for p t = 2 – 4.5 GeV/c Raimond Snellings QM01 Saturated p T > 2GeV Huge Asymmetry !

32. v 2 (p t ) for high p t particles MG, I. Vitev and X.N. Wang, nucl-th/00012092 Raimond Snellings QM01 * Finite dE/dx ” v 2 (p t ) ™ 0 for p t ™ ¥ *

33. Preliminary STAR Charged particle anisotropy Raimond Snellings, STAR systm. error 10% - 20% for p t = 2 – 4.5 GeV/c l Kolb et al (Hydro) + MG, P. Levai, I.Vitev (dE QCD /dx) PRL85(00)5535 M G, I.Vitev and X.N. Wang, nucl-th/00012092, PRL in press Constraint on dE/dx µ r glue µ dN glue /dy l Differential v 2 (p T ): Hydro up to ~1.5 GeV followed by saturation l Constraint on Initial Conditions: dNglue/dy > 500 Is This consistent with Single Inclusive Quenching? STAR: Phys.Rev.Lett.86(01)402

34. Comparison with p t distribution l calculation compatible with l anisotropy measurement l and p t - spectra Hydro+GLV: M. Gyulassy, I. Vitev and X.N. Wang, nucl-th/00012092

35. Summary l Only 4 months after the first 3 week run at RHIC PHENIX and STAR reported striking new high-p t data at QM01 l for charged and identified particles p t spectra to 4 - 6 GeV l azimuthal angular correlation out to 4.5 GeV l Peripheral collisions are well reproduced by pQCD (TAB scaled pp) l Central collisions show clear deviation from scaled p-p extrapolation l While Premature to draw definite or quantitative conclusions it appears (to me) that a (gluon) plasma with at least 100 times nuclear matter density was produced in Au+Au at Ecm=130 AGeV l RHIC run 2001: Vastly higher statistics with both Au+Au and p+p at Ecm=200 AGeV will probe out to pT>10 GeV high-p t data are consistent with “jet quenching” predictions !

36. A phase transition as seen from CERN - the skier can move further … a new phase develops - A skier (quark) is confined inside snow patches (hadrons) - the skier (quark ?) can move freely over long distances … Luciano Maiani, CERN February 2000

37. - A skier (quark jet) easily passes through cold, color white snow (a hadronic medium) -At higher energies some of snow melts and jets have harder time getting to lodge (the mixed phase) -At RHIC the snow melts. Skiers (and jets) D » break their legs passing through opaque colorful matter (the QGP) M.G., KFKI February 2001 A phase transition as seen by jet at RHIC