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RHIC Heavy Ion Physics Summary: Flowing from the past through the present to a luminous future

RHIC Heavy Ion Physics Summary: Flowing from the past through the present to a luminous future. William Christie Brookhaven National Laboratory. Outline. Brief introduction to the RHIC Collider and Detectors Major discoveries in the past decade at RHIC

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RHIC Heavy Ion Physics Summary: Flowing from the past through the present to a luminous future

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  1. RHIC Heavy Ion Physics Summary:Flowing from the past through the present to a luminous future William Christie Brookhaven National Laboratory DIS April 2010 W.B. Christie

  2. Outline • Brief introduction to the RHIC Collider and Detectors • Major discoveries in the past decade at RHIC • Matter at high temperature flows with low viscosity “Perfect Liquid” • Importance of Constituent quarks in Hadronization? Constituent quark scaling for v2 • Matter at high temperature is opaque to QCD-colored partons “Jet Quenching” • Some recent RHIC Results • Measurement of early temperature • Possible evidence for parity violation • Look for evidence of Color Glass Condensate • First observation of anti-Hypernucleus • Complementary program: Search for the QCD Critical Point • Present and future: investigate new phenomena Quantitatively Upgrades to accelerator and experiments for running well into the next decade DIS 2010 W.B. Christie

  3. PHOBOS BRAHMS &PP2PP RHIC PHENIX 1.2 km STAR RHIC Implementation • Flexibility is key to understanding complicated systems • Polarized protons, sqrt(s) = 50-500 GeV • Nuclei from d to Au (U), sqrt(sNN) = 5-200 GeV • Physics runs to date • Au+Au @9,20,39,62,130,200 GeV • Cu+Cu @22,62,200 GeV • Polarized p+p @200 & 500 GeV • d+Au @ 200 GeV DIS 2010 W.B. Christie

  4. FCAL PHENIX Present + Upgrades Charged Particle Tracking: Drift Chamber Pad Chamber Time Expansion Chamber/TRD Cathode Strip Chambers(Mu Tracking) Forward Muon Trigger Detector Si Vertex Tracking Detector- Barrel Si Vertex Endcap (mini-strips) Particle ID: Time of Flight Ring Imaging Cerenkov Counter TEC/TRD Muon ID (PDT’s) Aerogel Cerenkov Counter Multi-Gap Resistive Plate Chamber ToF Hadron Blind Detector Calorimetry: Pb Scintillator Pb Glass Nose Cone Calorimeter Muon Piston Calorimeter Event Characterization: Beam-Beam Counter Zero Degree Calorimeter/Shower Max Detector Forward Calorimeter Reaction Plane Detector FCAL SMD/ 4

  5. STAR Present + Upgrades • Particle ID: • Full Barrel ToF • Calorimetry: • Photon Multiplicity Detector (PMD) • Barrel EMC • Endcap EMC • Forward Meson Spectrometer • Charged Particle Tracking: • Main TPC • Forward TPC (FTPC) • SSD + Intermediate Tracker +Active Pixel Detector = HFT(was SSD+SVT) • Forward GEM Tracker • Event Characterization & Trigger: • Beam-Beam Counter (BBC) • Zero Degree Calorimeter (ZDC) • Forward Pion Detectors (FPD)

  6. z y x isotropic directed elliptic higher harmonics Collective Behavior: Azimuthal Anisotropy v2 Pressure converts initial coordinate-space anisotropy into final momentum-space anisotropy py px initial spatial anisotropy anisotropy in momentum space 6 DIS 2010 W.B. Christie

  7. The Flow is ~Perfect • Huge asymmetry found at RHIC • massive effect in azimuthal distribution w.r.t reaction plane • At higher pT: Factor 3:1 peak to valley from 25% v2 • The “fine structure” v2(pT) below ~ 2 GeV/c for different mass particles shows good agreement with ideal (zero viscosity, λ=0) hydrodynamics • “perfect liquid” • Appealing picture: • Nearly perfect fluid with local thermal equilibrium established at <~1 fm with a soft equation of state containing a QGP stage 2v2 7 Hydro calculations: Kolb, Heinz and Huovinen

  8. Elliptic Flow STAR Whitepaper, Nucl. Phys. A 757 (2005) 102 Second Fourier harmonic v2 large at RHIC For the first time approaching hydrodynamic predictions DIS 2010 W.B. Christie

  9. Breakdown of hydrodynamics: v2 vs. pT Large values indicate strong sensitivity to the system geometry for production at all measured pT v2 at intermediate pT is grouped by quark number Intermediate pT PRL 92 (2004) 052302; PRL 91 (2003) 182301 DIS 2010 W.B. Christie

  10. Partonic flow:Scaling of v2 with Number of Constituent Quarks Scale pT and v2 with number of constituent quarks (2 for mesons, 3 for baryons) Low pT: scaling fails (hydrodynamics) Intermediate pT: works rather well (to 5-10%) Flow develops among partons that coalesce into hadrons STAR Preliminary (M.Oldenburg, QM2005) DIS 2010 W.B. Christie

  11. The Promise of Jet Tomography • Simplest way to establish the properties of a system • Calibrated probe • Calibrated interaction • Suppression pattern tells about density profile • Heavy ion collisions • Hard processes serve as calibrated probe • Suppression provides density measure + = DIS 2010 W.B. Christie

  12. Calibrated Probe: Hard Interactions S.S. Adler et al, Phys. Rev. Lett. 91 (2003) 241803 • Hard interactions well understood in perturbative QCD • Factorization holds • PDF (initial) x NLO x FF (final) • Example: p0 production well reproduced down to 2 GeV • Numerous other examples • p0 in the forward direction, STAR PRL 92 (2004) 1718 STAR PRL 97 (2006) 152302. • proton production in p+p, STAR PLB 637, (2006)161. • Direct g production PHENIX PRD 71 (2005) 071102 • Jet production in p+p, STAR PRL 97 (2006) 252001 • Significant uncertainties in the calculations, so for precision the baseline needs to be measured p+p→p0+X KKP Fragmentation (Data – pQCD)/pQCD DIS 2010 W.B. Christie

  13. Binary collision scaling p+p reference Application to Heavy Ion Collisions: Initial Results Strong suppression in Au+Au collisions, no suppression in d+Au:  Effect is due to interactions between the probe and the medium Established use as a probe of the density of the medium Conclusion: initial medium is dense (20-100x nuclear matter density) PHENIX: Phys. Rev. Lett. 91 (2003) 072301 STAR: Phys. Rev. Lett. 91 (2003) 072304 PHOBOS: Phys. Rev. Lett. 91 (2003) 072302 BRAHMS: Phys. Rev. Lett. 91 (2003) 072303 DIS 2010 W.B. Christie

  14. Calibrated Interaction? Grey Probes Wicks et al, Nucl. Phys. A784 (2007) 426 • Problem: interaction with the medium so strong that information lost: “Black” • Significant differences between predicted RAA, depending on the probe • Experimental possibility: recover sensitivity to the properties of the medium by varying the probe DIS 2010 W.B. Christie

  15. Charm/Beauty: No shade of gray STAR, PRL 98 (2007) 192301 PHENIX, PRL 98 (2007) 172301 • Unexpectedly strong suppression of non-photonic electrons a major issue • Calls into question the calibration of the interaction of the probe with the medium • Uncertainties in B contribution: need to measure c and b separately (future) DIS 2010 W.B. Christie

  16. Possible evidence for local parity violation Theoretical Idea in a Nutshell L or B DIS 2010 W.B. Christie Chiral Magnetic Effect Local fluctuations in topological charge + Large (QED) Magnetic Field = Separation of Charges along Magnetic Field Direction (Electric current induced by magnetic field) Violates local Parity Symmetry 16

  17. Theoretical Basis Energy of gluonic field is periodic in NCS (Chern-Simons number) direction. NCS= -2 -1 0 1 2 Instantons and sphalerons are localized (in space and time) solutions describing transitions between different vacuavia tunneling or go-over-barrier Picture from H. Warringa, Moriond 2009 17 States of non-zero topological charge leads to imbalanced chirality: Number of left-handed objects ≠ Number of right-handed

  18. Chirality imbalance in a magnetic field Negative Charge Spin Momentum Positive Charge Spin aligned with momentum Spin aligned with magnetic field*charge Therefore Momentum aligned with magnetic field*charge Electric Current along Magnetic Field 18 DIS 2010 W.B. Christie

  19. Application to Heavy Ion Physics L or B 19 Incoming charged nuclei: Very large Magnetic Field perpendicular to the reaction plane (~1017 Gauss) Nonzero topological charge: Separation of charges above and below the reaction plane

  20. Observation Phys. Rev. Lett. 103 (2009) 251601 20 DIS 2010 W.B. Christie Large non-zero signal: same-sign particles prefer to be on the same side of the observed reaction plane Do we declare success? Observable not Parity Odd Trivial correlations can contribute to signal Current models cannot reproduce data with trivial correlations alone

  21. The beginnings of a program Need to vary conditions to rule out trivial explanations U U 21 DIS 2010 W.B. Christie Beam Energy Scan • Vary the magnetic field in both strength and duration • Necessary condition: free quarks and gluons. When does this disappear? Uranium+Uranium Trivial correlations + no magnetic field: Does the signal disappear? Isobars: vary the magnetic field keeping trivial correlations fixed Does the signal change?

  22. arXiv:0804.4168v1 , PRL in press Early Temperature, Thermal radiation e+ Low mass, high pT e+e- nearly real photons Large enhancement above p+p in the thermal region  e-  pQCD  spectrum (Compton scattering @ NLO) agrees with p+p data PHENIX, PRL104: Recent PHENIX Result

  23. 23 direct photons: Tinit > Tc ! • Exponential fit in pT: Tavg = 221 ±23 ±18 MeV • Multiple hydrodynamics models reproduce data Tinit ≥ 300 MeV NB: Tc ~ 170 MeV

  24. Calibrated Probe? Initial state First look run 3, STAR PRL 97, 152302 (2006). • Conjectured Universal State of Matter when probed at High enough Energy: ColorGlassCondensate • May affect initial conditions for some places at RHIC and LHC • STAR: Forward Meson Spectrometer in d+Au 1/x DIS 2010 W.B. Christie

  25. p + p  p0 + X, s = 200 GeV Large rapidity p,K,p cross sections for p+p, s=200 GeV PRL 98 (2007) 252001 PRD 76 (2007) 051106 PRL 92 (2004) 171801 RHIC ProbesUnpolarized cross sections as benchmarks and heavy-ion references Good agreement between experiment and theory  calibrated hard scattering probes of proton spin and low-x gluons 26

  26. BRAHMS Observation - RdAu as function of rapidity PRL 94 (2004) Minimum bias with < Ncoll> = 7.2±0.3 Cronin like enhancement at = 0. Clear suppression as  changes up to 3.2 NdAu(pT,) RdAu= <Ncoll > Npp(pT, ) • dN/dptd for dAu decreases relative to pp as one goes to forward pseudorapidities. 27

  27. BRAHMS Rcp(central/peripheral) Result for dAu collisions At  =0 the central events have the ratio systematically above that of semi-central events. We see a reversal of behavior as we study events at  = 3.2 1/<Ncollcentral> NdAucentral(pT,) Rcp= 1/<Ncoll periph> NdAuperiph(pT, ) 28

  28. STAR Inclusive p0 production from dAu J. Adams et al. (STAR), PRL 97 (2006) 152302 Particle production cross sections for d+Au collisions are smaller than expectations from only shadowing at <h> =4.0, and the energy dependence is best described by CGC calculations (A. Dumitru et al. Nucl Phys A765 (2006) 464) 29 DIS April 2010 W.B. Christie

  29. Two forward pions can probe very low xg For plot: 1) Pythia simulation 3) Plot rapidity of all other pions between 1.5 GeV/c and pT of the trigger pion as function of x 2) Trigger on one p0 forward (3<h<4) with pT>2.5 GeV/c Forward-Forward FMS-FMS This region can be probed with FMS-endcap calorimeter Forward-Central FMS-Barrel calorimeter See Ermes Braidot, Quark Matter 2009 proceedings, arXiv:0907.3473 Forward-Forward probes lowest x 30

  30. Back-to-back Angular Correlations pQCD 22 process =back-to-back di-jet (Works well for p+p) Forward jet p d+Au in HIJING p Kharzeev, Levin, McLerran(NPA748, 627) Mid-rapidity jet With high gluon density 21 (or 2many) process = Mono-jet ? Mono-jet Dilute parton system (deuteron) PT is balanced by many gluons Dense gluonfield (Au) CGC predicts suppression of back-to-back correlation Conventional shadowing changes yield, but not angular correlation 31 DIS 2010 W.B. Christie

  31. Centrality dependence of forward di-pion decorrelation dAu peripheral dAu data dAu central Away-side peaks evident in peripheral dAu and pp. Away-side peaks in peripheral dAu are roughly 50% wider than in pp. Significant dependence on centrality is evident in azimuthal decorrelation. Leading PT pion > 2.0 GeV dAu all data pp data 32

  32. Comparison w/ Marquette CGC calculation CGC with Q02=1.5 GeV2 CM doing b strips to make better comparison Cyrille Marquet: arXiv:0708.0231 Nucl.Phys.A796:41-60,2007 b=0 • Jet-like correlations of forward dipions produced in p+p collisions require a rapidly rising gluon density at low x, consistent with HERA data. • Away-side forward di-pion correlations are strongly suppressed in central d+Au collisions • CGC calculation “predicts” away-side peak disappearance for central d+Au • Suggests that Gluon saturation occurs at momentum fractions and scales that are relevant to RHIC collisions, based on qualitative consistency between measurement and color-glass condensate expectations of away-side peak disappearance for forward dipion correlations 33

  33. Anti-hypertriton 34 DIS 2010 W.B. Christie • Study of hypernuclei a component of worldwide effort: GSI, J-PARC, Jefferson Lab, …, and now RHIC • RHIC: first observation of an Anti-hypernucleus • First article from RHIC in Science: Science Express March 4, 2010

  34. RHIC Program on Anti-nuclei RHIC uniquely capable in producing anti-nuclei in a range of forms • Many antiprotons and antineutrons, coalescence effective Future tests of matter-antimatter symmetry in the Nuclear Force • Range of other antinuclei in reach, precise measurements of properties • Spurring new ideas: atomcules (bound states of proton+antiproton, …) 35

  35. Critical Point Search • Critical Point a key marker on the QCD phase diagram • High energy: Crossover • Low energy: 1st order • In between: Critical point • Lower beam energy: increase baryon chemical potential, scan around critical point • Program starting in 2010 DIS 2010 W.B. Christie

  36. Future at RHIC: “RHIC II” or the fb era STAR HFT Year 7 • RHIC: luminosity + upgraded detectors for precision • Beauty: last hope for a “grey” probe; needs detector upgrades to both STAR and PHENIX to isolate from charm • g-jet: precision probe of energy loss • Upsilon: precision tests of Debye screening with a “standard candle” Year 4 PHENIX VTX One year at RHIC II ~ 30 nb-1 30 nb-1*1972 =~ 1 fb-1 p+p equivalent DIS 2010 W.B. Christie

  37. Summary • Major discoveries in the past decade at RHIC • Matter at high temperature flows with low viscosity: “Perfect Liquid” • “Constituent quark scaling” • Matter at high temperature is opaque to QCD-colored partons • “Jet Quenching” • Recent Results • Evidence for possible local parity violation in strong interaction • First measurement of temperature beyond the QCD phase boundary • Signatures consistent with Colored Glass Condensate observed • First observation of Anti-Hypernucleus • Present and future: investigate new phenomena Quantitatively • Upgrades to accelerator and experiments for running well into the next decade • Complementary program: Search for the QCD Critical Point 38 DIS 2010 W.B. Christie

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