Quark Gluon Plasma Recent Advances

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1 Quark Gluon Plasma Recent Advances Lawrence Berkeley National Laboratory LP01, Rome, July 2001

2 Introduction P.C. Sereno et al. Science, Nov. 13, 1298(1998). (Spinosaurid) We may not see the entire body ever... LP01, Rome, July

Physics of Heavy Ion Program Study of hadronic matter at the highest energies Two nuclei approach each other, relativistically contracted to thin pancakes Hard collisions dominate first instants of

3 Physics of Heavy Ion Program Study of hadronic matter at the highest energies Two nuclei approach each other, relativistically contracted to thin pancakes Hard collisions dominate first instants of collision Produced particles reinteract at hard and soft scales Final state particles freeze-out and stream towards the detectors Possible creation of a Quark-Gluon Plasma (QGP) LP01, Rome, July

4 F. Karsch, hep-lat/ QCD Predictions Lattice QCD: phase transition at ε ~ 1 GeV/fm 3 but, fully thermalized (equilibrated) system Under certain assumptions (Bjorken hydro): CERN: ε~3.0 GeV/fm 3 RHIC: ε~4.5 GeV/fm 3 LP01, Rome, July Energy density for QGP formation reached!

5 Seeing deconfined matter in HI collisions Heavy ion collisions are highly dynamic: can we see deconfined phase even if it is produced? Some observables: Deconfinement: suppression of J/ψ High energy density: interaction of jets with medium High temperature: direct photons Non-hadronic degrees of freedom: charge fluctuations Quasi-equilibrium at early stage: flow Large entropy density: hadron multiplicities Threshold behaviour: must be able to turn effects off No fundamental theory of heavy ion collisions discovery will rest on consistent picture from many observables LP01, Rome, July

6 CERN - NA35/NA49: strangeness enhancement Pb+Pb at 158 GeV/c S+S, S+Ag at 200 GeV/c Kaons represent ~ 70% of strangeness Increase over pp/pa ~ factor 2 LP01, Rome, July

7 Particle ratios AGeV 158 AGeV AGeV 158 AGeV / π - K / π + K STAR E802 E866 / E917 NA49 NA s (GeV) s (GeV) (QM 2001, C. Blume/NA49) Non-monotonic energy dependence in K + / π + Monotonic energy dependence in K - / π - LP01, Rome, July

8 WA97/NA57 Multistrange hyperons Ω enhancement ~ factor ; saturation at ~ 100 participants LP01, Rome, July

9 Ω departure... LP01, Rome, July

10 J/ψ suppression in central Pb+Pb collisions LP01, Rome, July

11 Low mass dilepton enhancement LP01, Rome, July

12 What next? HI at Bevalac/AGS/SPS: several suggestive results but no clear discovery SPS RHIC LHC... changes: smaller crossing time of two nuclei larger initial energy density larger freeze-out volumes longer lifetime larger freeze-out temperature smaller baryonic chemical potential increasing role of quark and gluon degrees of freedom LP01, Rome, July

13 PHOBOS BRAHMS First RHIC Run PHENIX STAR LP01, Rome, July

14 Relativistic Heavy Ion Collider Goal: IDENTIFY and STUDY the properties of QGP in high energy heavy ion collisions RHIC environment: Highest energy density ever produced in lab Au-Au collisions with total s= 25TeV About 4000 charged particle per central collision 12 June: 1 st s = 56 AGeV 24 June: 1 st s = 130 AGeV 5 Sept: end of first Au-Au physics run First Physics! July 12, 2001: start of second physics run July 17, 2001: 1 st s = 200 AGeV LP01, Rome, July

15 Au on Au Event at CM Energy ~ 130 AGeV Data Taken June 25, STAR TPC Pictures from Level 3 online display. LP01, Rome, July

16 Full Energy!!! Au+Au at AGeV STAR TPC - July 18, 2001 LP01, Rome, July

17 Offline Reconstruction (Au+Au at 130 GeV) (modest multiplicity shown so details are visible) All hits and tracks: - red = low pt - violet = high pt Hits not assigned to tracks: mostly low momentum spirals LP01, Rome, July

acceptance, multi-arm spectrometer PHOBOS: Si-based, large

18 Particle Identification (i) STAR kaons protons deuterons pions electrons BRAHMS: Small acceptance spectrometers PHENIX: Small acceptance, multi-arm spectrometer PHOBOS: Si-based, large acceptance STAR: TPC-based large acceptance LP01, Rome, July

19 Particle Identification (ii) Ω + +Ω φ from K + K - pairs Ξ Ξ Λ + π p + π LP01, Rome, July

20 π 0 PHENIX π 0 γ γ p T > 2.5 GeV STAR LP01, Rome, July

21 dn ch /dη for central collisions Normalized per participant nucleon dn ch /dη/(0.5n part ) s 1/2 (GeV) UA5 Fermilab ISR NA49 PHOBOS STAR PHENIX BRAHMS HIJING1.35 Saturation Model with quenching Au+Au(b<3 fm) pp (p pbar) No jet quenching LP01, Rome, July Four experiments agree to ~10%!! - ~40% increase relative to pp/pbar-p more violent collisions, significant increase in particle production - model killer: eliminates several models that predicted very large multiplicities

22 Longitudinal expansion CERN data: RHIC data: NA49 Higher yields at higher energy Shape difference LP01, Rome, July

23 Space-time Evolution of the H I Collisions 3. freeze-out 2. hot / dense time quark-gluon plasma 1. formation This talk: ~reverse chronological order LP01, Rome, July

24 Kinetic Freeze-out 3. freeze-out elastic scattering stops 2. hot / dense time quark-gluon plasma 1. formation Radial flow of matter (central coll.): common velocity boost -> stiffer momentum spectrum for more massive particles LP01, Rome, July

25 Kinetic Freeze-out (i) Pasi Huovinen et al, hep-ph/ T = T fo + mass β 2 r β r collective radial velocity LP01, Rome, July Hydrodynamic model predictions fit well!

26 Simple hydrodynamics: T apparent =T freezeout + mass * β 2 RadialFlow Kinetic Freeze-out (ii) Explosive expansion at RHIC! LP01, Rome, July

27 Chemical Freeze-out 3. freeze-out 2. hot / dense time quark-gluon plasma 1. formation inelastic scattering stops Yield ratios at chemical freezout reflect chemistry of matter LP01, Rome, July

28 Chemical Freeze-out (i) Measured particles: π, K, p, ϕ, Λ, Ξ, Ω, d, and their antiparticles Thermal fit to data: T ch = MeV µ = 15 q MeV µ 4 s MeV N.Xu, M.Kaneta nucl-ex/ LP01, Rome, July

29 Chemical Freeze-out (ii) pbar/p ratio ~ 0.65 Phys. Rev. Lett., 86, 4668 (2001). Near Net-Baryon Free At RHIC! LP01, Rome, July

30 Phase Diagram at Chemical Freeze-out Put parameters from Thermal Model fits on the phase diagram: Lattice QCD predictions Neutron star parton-hadron phase boundary LP01, Rome, July

31 Early Stage Collisions 3. freeze-out 2. hot / dense time quark-gluon plasma 1. formation creation of high mass, high momentum objects Gluon saturation Parton energy loss Elliptic flow LP01, Rome, July

32 High pt hadrons: inclusive spectra High pt hadrons jet1 jet2 -Wang&Gyulassy: Jet traversing high energy density medium loses energy -High energy density large suppression of high pt hadrons -Jets probe system at early time - SPS: No evidence of hadron suppression at high pt LP01, Rome, July

33 High p T hadrons from STAR and PHENIX STAR preliminary (central) 1/N evt 1/2π 1/p t dn/dp t (GeV/c) -2 PHENIX (centrality dependence) h + + h PHENIX preliminary 5% 5-15% 15-30% 30-60% 60-80% 80-92% UA1 ref data LP01, Rome, July UA1(130) scaled to 5% central scaled to 80-92% central p t (GeV/c)

34 Ratio STAR/UA1 vs pt: hadron suppression! Scaling factors: energy dependence, nuclear geometry Increases to 2 GeV/c Never Reaches 1! Parton energy loss (JET QUENCHING?) Perhaps, BUT Large Systematics ~30% Extrapolation of UA1 Intriguing LP01, Rome, July

35 Agreement of STAR and PHENIX results! RHIC/INT Workshop, Berkeley, May 2001: R AA STAR h - PHENIX (h + +h - )/2 preliminary CERN SPS binary scaling upper limit of error p t (GeV/c) LP01, Rome, July

36 Azimuthal Anisotropy - Eliptic Flow z Origin: spatial anisotropy of the system when created and rescattering of evolving system spatial anisotropy momentum anisotropy x x Sensitive to initial/final conditions and equation of state (EOS)! y Almond shape overlap region in coordinate space Reaction-plane: x-z plane ε = y2 x 2 y 2 + x 2 LP01, Rome, July v 2 = φ = atan cos2φ p p y x

37 The most central collisions agree with HYDRO suggesting that early-time thermalization may be completed v 2 : 2 nd Fourier harmonic coefficient of azimuthal distribution of particles with respect to the reaction plane (large v2 implies hydrodynamic evolution) STAR, PRL 86 (2001) 402 data Hydro STAR central collisions LP01, Rome, July

38 Event Anisotropy v 2 vs. Energy and pt 1) Elliptical flow v 2 increases with collision energy early thermalization? 2) Mass dependence typical hydrodynamic behavior! LP01, Rome, July

39 Summary: new era in study of ultra-relativistic heavy ion collisions data variety and quality confirms that the potential of the machine is truly fascinating ~Ideal conditions for QGP formation: Net-baryon density small (~ zero!) qgp? Parton energy loss? Explosive expansion! + evidence for: early equilibrium and high energy density LP01, Rome, July

40 It is clearly too early to draw definite conclusions, or to make firm statements about how data fit theoretical expectations. To a large extent RHIC results do not change the picture that has emerged from the analysis of AA collisions performed earlier. However, there are few instances where natural extrapolation does not work first glimpses of non trivial QCD behaviour in bulk nucleus-nucleus collisions????? LP01, Rome, July

41 LHC heavy ion experiments ALICE: dedicated HI experiment, 900 collaborators CMS: pp experiment with approved Heavy Ion program, <50 HI physicists LP01, Rome, July

42 EXTRA SLIDES Not to be shown during the talk perhaps for the discussion if needed

43 sketch of identified π+/π acceptances (year 1) pt (GeV/c) GeV/c STAR RICH charged particles (no pid): pt < GeV/c (limited by momentum resolution) PHENIX STAR TPC de/dx BRAHMS (luminosity limited) PHOBOS rapidity LP01, Rome, July

44 sketch of K+/K- acceptances (year 1) PHENIX RICH (4<pT<12 GeV/c) pt (GeV/c) GeV/c STAR RICH, KINKS IN TPC PHENIX TOF 1.0 BRAHMS (luminosity limited) 0.5 STAR TPC de/dx PHOBOS LP01, Rome, July rapidity

45 sketch of p/pbar acceptances (year 1) pt (GeV/c) GeV/c STAR RICH 4 GeV/c PHENIX 1.5 Not shown: "plus minus minus" PHOBOS STAR TPC de/dx BRAHMS (luminosity limited) LP01, Rome, July rapidity

46 Wroblewski Factor µ B 0 µ B = 0 P. Braun-Munzinger, J. Cleymans, H. Oeschler, and K. Redlich, hep-ph/ T max T C 170 MeV K + /π + ~ Λ/π + LP01, Rome, July

47 Event Anisotropy v 2 Sensitive to initial/final conditions and equation of state (EOS)! coordinate-space-anisotropy momentum-space-anisotropy y p y x p x ε y y 2 x + x 2 = 2 2 v 2 = cos2ϕ, ϕ = tan 1 ( p p y x ) LP01, Rome, July

48 Elliptic Flow v 2 (i) Coordinate Space Momentum Space p y parton scatterings hadron p x Hydrodynamic! ε = y2 x 2 y 2 + x 2 v 2 = cos2φ φ = atan p p y x LP01, Rome, July

Elliptic Flow v 2 (ii) Probe the state of the matter created in the collision Relatively early information of the collision ``Elliptic flow in Au+Au collisions at snn = 130 GeV, A. Poskanzer, R.

49 Elliptic Flow v 2 (ii) Probe the state of the matter created in the collision Relatively early information of the collision ``Elliptic flow in Au+Au collisions at snn = 130 GeV, A. Poskanzer, R. Snellings, Phys. Rev. Lett. 86, 402(2001) Elliptic flow v 2 SPS STAR preliminary Pseudo-rapidity η Transverse momentum p t (GeV/c) A factor of 2-3 increase from SPS to RHIC! LP01, Rome, July Mass dependent of flow, contrary to SPS, consistent with hydrodynamic model!

50 Geometry of STAR TPC is the heart of STAR TPC arrives at BNL from LBL on 11/6/97 LP01, Rome, July

51 Schematic Phase Diagram of Strongly Interacting Matter Temperature ~150 MeV early universe Quark Gluon Plasma ε ~ 1 GeV/fm 3 Hadronic Matter normal matter neutron stars LP01, Rome, July ~ 1.5 GeV Quark Gluon Plasma: extended volume of freely propagating quarks and gluons (seen in Lattice QCD) Can we create and study it in the laboratory? high energy collisions of heavy nuclei Baryochemical potential

52 Ultra-peripheral collisions γγ, γ-pomeron interactions Signature: back-to-back opposite charges Au+Au --> Au+Au + ρ 0 STAR preliminary STAR preliminary LP01, Rome, July

53 LP01, Rome, July

54 Full Energy!!! Au+Au at AGeV LP01, Rome, July

The Physics of RHIC Peter Jacobs Lawrence Berkeley National Laboratory

The Physics of RHIC Peter Jacobs Lawrence Berkeley National Laboratory Why collide nuclei at high energy? RHIC: machine and experiments Physics from the first year of RHIC Outlook SLAC, Nov 13, 2001 The