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Experimental Results from RHIC: QGP or what?

Experimental Results from RHIC: QGP or what?. M. J. Tannenbaum Brookhaven National Laboratory Upton, NY 11973 USA. See nucl-ex/0410003-PHENIX nucl-ex/0410020-BRAHMS nucl-ex/0410022-PHOBOS nucl-ex/0501009-STAR. RHIC&AGS Users Meeting June, 2005.

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Experimental Results from RHIC: QGP or what?

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  1. Experimental Results from RHIC: QGP or what? M. J. Tannenbaum Brookhaven National Laboratory Upton, NY 11973 USA See nucl-ex/0410003-PHENIX nucl-ex/0410020-BRAHMS nucl-ex/0410022-PHOBOS nucl-ex/0501009-STAR RHIC&AGS Users Meeting June, 2005 MJT-RHIC&AGS Users June 2005

  2. WarningBeware of Theory Curves on Experimental Data MJT-RHIC&AGS Users June 2005

  3. Original observation of Drell-Yan pairs: “massive muon pairs in hadron collisions” MJT-RHIC&AGS Users June 2005

  4. The Measurement MJT-RHIC&AGS Users June 2005

  5. Theorists at Work MJT-RHIC&AGS Users June 2005

  6. The Measurement with “theory” curve MJT-RHIC&AGS Users June 2005

  7. The Truth-the clarity of Hindsight NA50 PLB 477, 28 (2000) MJT-RHIC&AGS Users June 2005

  8. STAR RHIC: Experiments MJT-RHIC&AGS Users June 2005

  9. Example of a central Au+Au event at snn =200 GeV dnch/d=0 =700 for central Au+Au collisions cf. 2.5 for p-p collisions MJT-RHIC&AGS Users June 2005

  10. Run Year Species s1/2 [GeV ] Ldt Ntot p-p Equivalent Data Size 01 2000 Au+Au 130 1 mb-1 10M 0.04 pb-13 TB 02 2001/2002 Au+Au 200 24 mb-1 170M 1.0 pb-110 TB p+p 200 0.15 pb-1 3.7G 0.15 pb-1 20 TB 03 2002/2003 d+Au 200 2.74 nb-1 5.5G 1.1 pb-146 TB p+p 200 0.35 pb-1 6.6G 0.35 pb-1 35 TB 04 2003/2004 Au+Au 200 241 mb-1 1.5G 10.0 pb-1 270 TB Au+Au 62 9 mb-1 58M 0.36 pb-1 10 TB 05 2004/2005 Cu+Cu 200 3.06 nb-1 1.1G 12.5 pb-1 Cu+Cu 62 185 mb-1 413M 0.76 pb-1 p+p 200 pb-1 pb-1 p+p 405 pb-1 pb-1 Run-1 to Run-5 Capsule History MJT-RHIC&AGS Users June 2005

  11. Energy Density MJT-RHIC&AGS Users June 2005

  12. =1/<mT> Spacetime evolution is important MJT-RHIC&AGS Users June 2005

  13. Ncharged, ET exhibit(&could determine) the Nuclear Geometry Define centrality classes: ZDC vs BBC Extract N participants: Glauber model ET EZDC b QBBC Nch PHENIX PHENIX Nch ET MJT-RHIC&AGS Users June 2005

  14. Colliding system expands: Energy  to beam direction per unit velocity || to beam pR2 • e 4.6 GeV/fm3 (130 GeV Au+Au) 5.5 GeV/fm3 (200 GeV Au+Au) 2ct0 well above predicted transition! Is the energy density high enough? PRL87, 052301 (2001) EMCal measures Bj MJT-RHIC&AGS Users June 2005

  15. Particle Production MJT-RHIC&AGS Users June 2005

  16. Semi-Inclusive soft particle spectra Au+Au central (b < 2.6 fm) • <pT>:  < K < p • 25% () to 40% (p) increase from peripheral to central Hydro QCD D.d'Enterria &D. Peressounko nucl-th/0503054 MJT-RHIC&AGS Users June 2005

  17. dN/x dx p < 2 p=2 p > 2 x = Inclusive pT spectra are Gamma Distributions MJT-RHIC&AGS Users June 2005

  18. Strong radial collective flow built-up at freeze-out: <bT> » 0.6 • pT ~ T T m Increase of <pT> with centrality--radial flow MJT-RHIC&AGS Users June 2005

  19. Particle ratios---inclusive and at high pT Au+Au sNN=200 GeV dramatic with centrality vs pT inclusive vs centrality-nothing much MJT-RHIC&AGS Users June 2005

  20. Assume all distrib. described by one T and one m: • 1 ratio (e.g. p/p) determines m/T • 2nd ratio (e.g. K/pi) provides T,m. • Then predict all other hadronic yields and ratios • n.b strangeness not suppressed s=1 dN ~ e - (E- m)/T d3p p/p ~ e – (E+m)/T/e –(E- m)/T = e - 2m/T Low pT (inclusive) ratios consistent with ``Thermal’’--but so are pp and e+ e- MJT-RHIC&AGS Users June 2005

  21. Lattice results Neutron STAR Phase Diagram from Thermal Fit of particle ratios---``chemical” • Final-state analysis suggests RHIC reaches the phase boundary • Hadron resonance ideal gas (M. Kaneta and N. Xu, nucl-ex/0104021 & QM02) • TCH = 175 ± 10 MeV • B = 40 ± 10 MeV • <E>/N ~ 1 GeV • (J. Cleymans and K. Redlich, Phys.Rev.C, 60, 054908, 1999 ) • Where is the QGP critical point? MJT-RHIC&AGS Users June 2005

  22. Are there fluctuations beyond random? • Event-by-event average pT (MpT) is closely related to ET • compare Data to Mixed events for random. • deviation expressed as: • FpT= MpTdata / MpTmixed -1 ~ few % • due to jets see PRL 93, 092301(04) MJT-RHIC&AGS Users June 2005

  23. What e-by-e tells you that you don’t learn from the inclusive average • e-by-e averages separate classes of events with different average properties, for instance 17% of events could be all kaons, and 83% all pions---see C. Roland QM2004, e-by-e K/ consistent with random. • A nice example I like is by R. Korus, et al, PRC 64, 054908 (2004): The temperature T~1/b varies event by event with T and T. MJT-RHIC&AGS Users June 2005

  24. Assuming all fluctuations are from T/T Very small and relatively constant with sNN CERES tabulation H.Sako, et al, JPG 30, S1371 (04) Where is the critical point? T/T MJT-RHIC&AGS Users June 2005

  25. Reaction Plane z y x py px Anisotropic (Elliptic) Transverse Flow--an Interesting complication in AA collisions • spatial anisotropy momentum anisotropy • Perform a Fourier decomposition of the momentum space particle distributions in the x-y plane • v2 is the 2nd harmonic Fourier coefficient of the distribution of particles with respect to the reaction plane MJT-RHIC&AGS Users June 2005

  26. STAR130 GeV Hydro predictions PRL 86, (2001) 402 more central  Centrality and pT dependence of v2 unidentified charged hadrons STAR 200 GeV (preliminary) • follows eccentricity of almond • saturates for pT >2 GeV/c MJT-RHIC&AGS Users June 2005

  27. Detailed comparison to hydrodynamics with identified particles--The perfect fluid (?) D.Teaney, PRC68, 034913 (2003) STAR-PRC-nucl-ex/0409033 MJT-RHIC&AGS Users June 2005

  28. Hard-Scattering:Jet (0) Suppression MJT-RHIC&AGS Users June 2005

  29. p-p Thermally-shaped Soft Production Hard Scattering RHIC pp spectra s=200 GeV nicely illustrate hard scattering phenomenology • Good agreement with NLO pQCD • this is no surprise for `old timers’ (like me) since single particle inclusive spectra were what proved QCD in the late 1970’s before jets. • Reference for A+A and p+A spectra • p0 measurement in same experiment allows us the study of nuclear effect with less systematic uncertainties. p0 PHENIX (p+p) PRL 91, 241803 (2003) MJT-RHIC&AGS Users June 2005

  30. -A DIS at AGS (1973)--Hard-Scattering is pointlike MJT-RHIC&AGS Users June 2005

  31. High pT in A+B collisions---TAB Scaling view along beam axis looking down • For point-like processes, the cross section in p+A or A+B collisions compared to p-p is simply proportional to the relative number of possible pointlike encounters • A for p+A, AB for A+B for the total rate • TAB the overlap integral of the nuclear profile functions, as a function of impact parameter b MJT-RHIC&AGS Users June 2005

  32. The anomalous nuclear enhancement a.k.a. the Cronin effect-- due to multiple scattering of initial nucleons (or constituents) What really Happens for p+A: RA > 1! • Known since 1975 that yields increase as A,  > 1  =1.1480.010 • J.W. Cronin et al.,Phys. Rev. D11, 3105 (1975) • D. Antreasyan et al.,Phys. Rev. D19, 764 (1979) MJT-RHIC&AGS Users June 2005

  33. Same for A+A at sNN= 17, 31 GeV Nuclear Modification Factor: MJT-RHIC&AGS Users June 2005

  34. For Au+Au at RHIC--strong suppression ! Au+Aup0 X (peripheral) Au+Aup0 X (central) Peripheral data agree well with Strong suppression in p+p (data & pQCD) scaled by TAB (Ncoll-) central Au+Au collisions MJT-RHIC&AGS Users June 2005

  35. RAA (0) AuAu:pp 200GeVHigh pT Suppression flat from 3 to 10 GeV/c ! Peripheral AuAu - consistent with Ncoll scaling (large systematic error) Binary scaling Factor 5 Large suppression in central AuAu - close to participant scaling at high PT Participant scaling PRL 91, 072301 (2003) MJT-RHIC&AGS Users June 2005

  36. PHENIX Run-1: RHIC Headline News … January 2002THE major discovery at RHIC (so far) PHENIX PRL 88, 022301 (2002) First observation of large suppression of high pT hadron yields ‘‘Jet Quenching’’? == Quark Gluon Plasma? MJT-RHIC&AGS Users June 2005

  37. PHENIX Collab. PRC 69, 034910 (2004) nucl-ex/0308006 Centrality RHIC Run 2 s=200 GeV: Comprehensive 0data vs centrality in Au+Au + 0 reference in p-p Au-Au nucl-ex/0304022 Phys. Rev. Letters 91, 072301 (2003) PHENIX MJT-RHIC&AGS Users June 2005

  38. Suppression: Final State Effect? • Hadronic absorption of fragments: • Gallmeister, et al. PRC67,044905(2003) • Fragments formed inside hadronic medium • Parton recombination (up to moderate pT) • Fries, Muller, Nonaka, Bass nucl-th/0301078 • Lin & Ko, PRL89,202302(2002) • Energy loss of partons in dense matter • Gyulassy, Wang, Vitev, Baier, Wiedemann… See nucl-th/0302077 for a review. MJT-RHIC&AGS Users June 2005

  39. r/ ggg Alternative: Initial Effects • Gluon Saturation • (color glass condensate: CGC) Wave function of low x gluons overlap; the self-coupling gluons fuse, saturating the density of gluons in the initial state. (gets Nch right!) hep-ph/0212316; D. Kharzeev, E. Levin, M. Nardi • Multiple elastic scatterings (Cronin effect) Wang, Kopeliovich, Levai, Accardi • Nuclear shadowing D.Kharzeev et al., PLB 561 (2003) 93 Broaden pT MJT-RHIC&AGS Users June 2005

  40. p q g q  p 2004--Direct Photons in Au+Au 200 GeV: follow TAB scaling from p-p for all centralities-no suppression • Direct photon production in Au+Au (all centralities) consistent w/ “TAB-scaled” pQCD. Proves that initial state Au structure function is simply a superposition of p-p structure functions including g(x). • outgoing Direct photons unaffected by QCD medium in Au+Au  0suppression is medium effect Submitted to PRL nucl-ex/0503003 MJT-RHIC&AGS Users June 2005

  41. Direct- measurement in s=200 GeV p-p (Subtraction) • NLO-pQCD calculation • Private communication with W.Vogelsang • CTEQ6M PDF. • direct photon + fragmentation photon • Set Renormalization scale and factorization scale pT/2,pT,2pT • The theory calculation shows a good agreement with our result • Confirms use of theoretical result as Au+Au comparison • Opens the way for measurement of gluon spin structure function from ALL MJT-RHIC&AGS Users June 2005

  42. d+Au: Control Experiment to prove the Au+Au discovery • The “Color Glass Condensate” model predicts the suppression in both Au+Au and d+Au (due to the initial state effect). • The d+Au experiment tells us that the observed hadron suppression at high pT central Au+A is a final state effect. • This diagram also explains why we can’t measure jets directly in Au+Au central collisions: all nucleons participate so charged multiplicity is ~200 times larger than a p-p collision 300 GeV in standard jet cone. d+Au Au+Au = cold medium = hot and dense medium Initial + Final State Effects Initial State Effects Only MJT-RHIC&AGS Users June 2005

  43. Cronin effect observed in d+Au at RHIC sNN=200 GeV, confirms x is a good variable PHENIX preliminary 0 d+Au vs centrality for DNP2003 MJT-RHIC&AGS Users June 2005

  44. This leads to our second PRL cover, our first being the original Au+Au discovery MJT-RHIC&AGS Users June 2005

  45. Theoretical Understanding? Both • Au-Au suppression (I. Vitev and M. Gyulassy, hep-ph/0208108) • d-Au enhancement (I. Vitev, nucl-th/0302002) understood in an approach that combines multiple scattering with absorption in a dense partonic medium  Our high pT probeshave been calibratedand are nowbeing used toexplore the precise propertiesof the medium See nucl-th/0302077 for a review. d-Au Au-Au MJT-RHIC&AGS Users June 2005

  46. Suppression is a Final State Medium Effect • Energy loss of partons in dense matter--A medium effect predicted in QCD---Energy loss by colored parton in medium composed of unscreened color charges by gluon bremsstrahlung--LPM radiation • Gyulassy, Wang, Vitev, Baier, Wiedemann… See nucl-th/0302077 for a review. • Baier,Dokshitzer,Mueller, Peigne, Shiff, NPB483, 291(1997),PLB345,277(1995), Baierhep-ph/0209038, • From Vitev nucl-th/0404052: Bj =15 GeV/fm3=10 x larger unscreened color charge density than in a nucleon MJT-RHIC&AGS Users June 2005

  47. Baier, et al: Screened Coulomb potential MJT: 2 plays role of tmin ... = 0.5 GeV/c=1/0.4 fm MJT-RHIC&AGS Users June 2005

  48. One Big Grape-but size of a nucleon Rep. Prog. Phys. 63 (2000) 1511 1.6fm 0.8fm  (1 - e-r)/r MJT-RHIC&AGS Users June 2005

  49. High pT particle High pT particle Au+Au p+p Jet Physics …jets in AuAu “difficult”--but STAR-Jet event in ppcollision STAR Au+Au collision MJT-RHIC&AGS Users June 2005

  50. syst. error Away STAR--Away jet is suppressed--consistent with energy loss • Select a ``trigger’’ particle 4<pT<6 GeV/c • 2< pTassoc < 4 GeV/c nucl-ex-0501009 nucl-ex/0501016 MJT-RHIC&AGS Users June 2005

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