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STAR at RHIC: Flowing from the past through the present to a luminous future

STAR at RHIC: Flowing from the past through the present to a luminous future

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STAR at RHIC: Flowing from the past through the present to a luminous future

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  1. STAR at RHIC:Flowing from the past through the present to a luminous future James Dunlop Brookhaven National Laboratory Pusan Colloquium James C Dunlop

  2. Outline • Major discoveries in the past decade at RHIC • Matter at high temperature flows with low viscosity: “Perfect Liquid” • Matter at high temperature is opaque to QCD-colored partons “Jet Quenching” 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 Pusan Colloquium James C Dunlop

  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 @9,20,62,130,200 GeV • Cu+Cu @22,62,200 GeV • Polarized p+p @200 GeV • d+Au @ 200 GeV Pusan Colloquium James C Dunlop

  4. STAR: A Correlation Machine Tracking: TPC Particle ID: TOF Electromagnetic Calorimetry: BEMC+EEMC+FMS (-1 ≤  ≤ 4) Heavy Flavor Tracker (2013) Forward Gem Tracker (2011) Full azimuthal particle identification over a broad range in pseudorapidity Pusan Colloquium James C Dunlop

  5. 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 Pusan Colloquium James C Dunlop

  6. Elliptic Flow STAR Whitepaper, Nucl. Phys. A 757 (2005) 102 Second Fourier harmonic v2 large at RHIC For the first time approaching hydrodynamic predictions Pusan Colloquium James C Dunlop

  7. v2 vs. Ideal Hydrodynamics Ideal hydrodynamics reproduces v2 relatively well Below pT~2 GeV, matches v2 and spectra to ~20-30% Appealing picture: Nearly perfect fluid with local thermal equilibrium established at <~1 fm with a soft equation of state containing a QGP stage STAR, Nucl. Phys. A 757 (2005) 102 Hydro calculations: Kolb, Heinz and Huovinen Pusan Colloquium James C Dunlop

  8. Analogy to Ultracold Atoms Extremely cold system at T=10 nK or 10^(-12) eV can produce micro-bang Elliptic flow with ultracold trapped Li6 atoms, a=> infinity regime The system is extremely dilute, but can be put into a hydro regime, with an elliptic flow, if it is specially tuned into a strong coupling regime via the so called Feshbach resonance Analogy pointed out by Shuryak Pusan Colloquium James C Dunlop

  9. How perfect is perfect? D. Teaney, Phys. Rev. C 68, 034913 (2003) First attempt at viscous effects: Large effect on v2 Conclusion: viscosity must be extremely small (near quantum lower bound?) Strong theoretical and experimental effort to precisely measure viscosity Pusan Colloquium James C Dunlop

  10. How perfect? Snapshot of current status A. Tang, QM2009 • Active investigation by theory and experiment using a wide range of techniques • Closing in on the answer: Between Superfluid He and conjectured quantum limit from string theory Pusan Colloquium James C Dunlop

  11. The Future: Charm v2 Now Future • Put a boulder in a stream: does it flow? • Answer appears to be yes Upgrades: more definitive answers • Especially important: direct D measurements in hydrodynamic pT range PHENIX, PRL 98 (2007) 172301 Pusan Colloquium James C Dunlop

  12. 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 Pusan Colloquium James C Dunlop

  13. 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) Pusan Colloquium James C Dunlop

  14. 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 + = Pusan Colloquium James C Dunlop

  15. Binary collision scaling p+p reference Application to Heavy Ion Collisions: Initial Results Strong suppression in Au+Au collisions, no suppresion 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 (at the time): medium is dense (50-100x 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 Pusan Colloquium James C Dunlop

  16. 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 Pusan Colloquium James C Dunlop

  17. 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 Pusan Colloquium James C Dunlop

  18. Central RAA Data Increasing density The Limitations of RAA: “Fragility” K.J. Eskola, H. Honkanken, C.A. Salgado, U.A. Wiedemann, Nucl. Phys. A747 (2005) 511 Surface bias leads effectively to saturation of RAA with density Challenge: Increase sensitivity to the density of the medium A. Dainese, C. Loizides, G. Paic, Eur. Phys. J. C38(2005) 461 Pusan Colloquium James C Dunlop

  19. Black and White S.S. Adler et al, Phys. Rev. Lett. 94, 232301 (2005) • Medium extremely black to hadrons, limiting sensitivity to density • Medium transparent to photons (white): no sensitivity • Is there something grey? Pusan Colloquium James C Dunlop

  20. 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 Pusan Colloquium James C Dunlop

  21. 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 Pusan Colloquium James C Dunlop

  22. Mechanisms for Energy Loss “Passage of Particles through Matter”, Particle Data Book • QED: different momenta, different mechanisms • Just beginning the exploration of this space inQCD Bremsstrahlung Radiative dE/dx Pusan Colloquium James C Dunlop

  23. Correlations • WMAP: 10-5 level • One sample • Only photons • Well-defined separation of sources • RHIC: 10-1 to 10-3 level • Multiple samples • Multiple probes • Separation of sources still under active investigation Pusan Colloquium James C Dunlop

  24. near STAR preliminary away AA/pp Leading hadrons pT (GeV/c) Medium Where does the energy go? • Lower the associated pT to search for radiated energy • Additional energy at low pT BUT no longer collimated into jets Active area: additional handles on the properties of the medium? Mach shocks, Cherenkov cones … e.g. Renk and Ruppert, Phys. Rev. C 73 (2006) 011901 0-12% 200 GeV Au+Au PHENIX preliminary STAR, Phys. Rev. Lett. 95 (2005) 152301 M. Horner, QM2006 Pusan Colloquium James C Dunlop

  25. d+Au, 40-100% Au+Au, 0-5% The Ridge: Dh-Df Correlations Phys. Rev. C73 (2006) 064907 mid-central Au+Au pt < 2 GeV • In Au+Au: broadening of the near-side correlation in  • Seen in multiple analyses • Number correlations at low pT • PRC73 (2006) 064907 • PT correlations at low pT, for multiple energies • Major source of pT fluctuations • J. Phys. G 32, L37 (2006) • J. Phys. G 34, 451 (2007) • Number correlations at intermediate pT • PRC 75, 034901 (2007) • Number correlations with trigger particles up to 8 GeV/c • D. Magestro, HP2005 • J. Putschke, QM2006 Dr/√rref 0.8< pt < 4 GeV STAR PRC 75(2007) 034901 3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig) Pusan Colloquium James C Dunlop

  26. STAR preliminary near Medium away mach cone near 0-12% 200 GeV Au+Au Medium away deflected jets How to interpret shape modifications? Hard-soft: away-side spectra approaching the bulk. Deflected jets, Mach-cone shock waves, Cherenkov radiation, completely thermalized momentum conservation, or…? • M. Horner, QM2006 STAR Collaboration, PRL 95,152301 (2005) Pusan Colloquium James C Dunlop

  27. d+Au Δ2 0-12% Au+Au 0-12% Au+Au: jet v2=0 Δ2 off-diagonal projection Δ1 Δ1 Df=(Df1-Df2)/2 Three particle correlations • Two Analysis Approaches: • Cumulant Method • Unambiguous evidence for true three particle correlations. • Two-component Jet+Flow-Modulated Background Model • Within a model dependent analysis, evidence for conical emission in central Au+Au collisions pTtrig=3-4 GeV/c pTassoc=1-2 GeV/c STAR PRL Pusan Colloquium James C Dunlop

  28. 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 Pusan Colloquium James C Dunlop

  29. STAR: A Correlation Machine Tracking: TPC Particle ID: TOF Electromagnetic Calorimetry: BEMC+EEMC+FMS (-1 ≤  ≤ 4) Heavy Flavor Tracker (2013) Forward Gem Tracker (2011) Full azimuthal particle identification over a broad range in pseudorapidity Pusan Colloquium James C Dunlop

  30. g-Jet: Golden Probe of QCD Energy Loss g • g emerges unscathed from the medium • Probes deeply into the medium: different surface bias from hadron, dihadron • Fully reconstructed kinematics: measure real fragmentation function D(z) h Pusan Colloquium James C Dunlop

  31. Gamma-Jet: unique capability of RHIC II RHIC: Clean separation of g from p0 W.Vogelsang NLO RHIC IIL= 20nb-1 LHC: 1 month run p0suppression at RHIC & LHC Pusan Colloquium James C Dunlop

  32. Gamma-Hadrons in the fb era Run-4 AuAu 0.2 nb-1 RHIC I AuAu 2 nb-1 RHIC II AuAu 20 nb-1 Projections for PHENIX From J. Nagle, Galveston STAR has somewhat higher statistics Thus, we can measure PRECISELY the modification of the fragmentation D’(z). First measurements made, but needs RHIC II luminosity to be conclusive Phys.Rev.C74:034906,2006. Phys.Rev.Lett.77:231-234,1996. Pusan Colloquium James C Dunlop

  33. STAR Jets in the fb era STAR PRL 97 (2006) 252001 Jet reconstruction under optimization In hand: p+p, Cu+Cu, Au+Au First results in hand as of now Developing technology for future application to RHIC-II and LHC 2 pb/GeV 40% precision with 0.3 pb-1,half barrel Pusan Colloquium James C Dunlop

  34. Quarkonium in the fb era: Upsilon RHIC Sequential dissociation of quarkonia to measure energy density of plasma Requires full luminosity of RHIC II for definitive measurements Proof of principle measurement: run 6 p+p Upsilon(1S+2S+3S)→e+e- Pusan Colloquium James C Dunlop

  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 starts in 2010 Pusan Colloquium James C Dunlop

  36. Critical Point Search: Signatures • Distinguishing feature of a critical point: long wavelength fluctuations • Search for fluctuation signatures that survive from the early stage • If the Critical Point is passed, reach 1st order phase transition • Search for non-monotonic signatures sensitive to transition • Example: Shape of final freezeout distribution from two-particle correlations Pusan Colloquium James C Dunlop

  37. Conclusion Major discoveries in the past decade at RHIC • Matter at high temperature flows with low viscosity: “Perfect Liquid” • Matter at high temperature is opaque to QCD-colored partons “Jet Quenching” 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 STAR has a bright past and an even brighter future Pusan Colloquium James C Dunlop

  38. Towards g-jet: (g,p0)-h Df Correlation analysis p+p From p+p collisions run 5, 2 pb-1 p0 Mixed Photon Use “shower-shapes” in EMC: Create two samples Enriched photon sample (mix g, p0) Enriched p0 sample (almost pure p0) Reduction in near angle peak in Photon sample Away-side yields only slightly reduced Effect more prominent for larger Ettrigger See Subhasis Chattopadhyay, QM2006 Pusan Colloquium James C Dunlop

  39. Preliminary Away-Side: pTtrig Dependence 1.3 < pTassoc < 1.8 GeV/c Away-side: • Structures depend on range of pT. • becomes flatter with increasing pTtrig • yield increases AuAu 0-12% Central contribution to away-side becomes more significant with harder pTtrig => fills dip Mark Horner, QM2006 6.0 < pTtrig < 10.0 GeV/c 3.0 < pTtrig < 4.0 GeV/c 4.0 < pTtrig < 6.0 GeV/c 0-12% Away side Pusan Colloquium James C Dunlop

  40. 10-20 GeV: Effects of the Medium Most Apparent STAR PRL nucl-ex/0604018 Majumder, et al. hep-ph/0611135 pT trigger > 8 GeV/c energy loss by 20 GeV jets accessible at RHIC (& interpretable) Pusan Colloquium James C Dunlop

  41. Dh-Df Two-Component Ansatz     3<pt,trigger<4 GeV pt,assoc.>2 GeV • Study near-side yields • Study away-side correlated yields and shapes • Components • near-side jet peak • near-side ridge • v2 modulated background Au+Au 0-10% preliminary Strategy:Subtract  from  projection: isolate ridge-like correlation Definition of “ridge yield”: ridge yield := Jet+Ridge()  Jet() Can also subtract large . Pusan Colloquium James C Dunlop

  42. Annual yields at RHIC II & LHC from Tony Frawley RHIC Users mtg. at LHC: (10-50) x s ~10% of L 25% running time Pusan Colloquium James C Dunlop

  43. Precision (and its limits) C. Loizides hep-ph/0608133v2 J. Lajoie [PHENIX] QM2006 Pusan Colloquium James C Dunlop

  44. NCC NCC HBD MPC MPC VTX & FVTX PHENIX Upgrades EMCAL 0 f coverage 2p EMCAL -3 -2 -1 0 1 2 3 rapidity (i) p0 and direct g with additional EM calorimeters (NCC, MPC) (ii) heavy flavor with silicon vertex tracker (VTX, FVTX) (i)+(ii) for large acceptance g-jet (iii) low mass dileptons (HBD) Pusan Colloquium James C Dunlop

  45. Other initiatives: Muons and dileptons • Muon Tracking Detector: use magnet steel as absorber • Physics: dileptons from intermediate mass up to quarkonia states • Best method for separating Upsilon states (a la CDF) • R+D stage: Brookhaven LDRD 2007-2008 • Dielectrons using TOF for ID and HFT for background rejection Pusan Colloquium James C Dunlop

  46. + c g e- K- g c e D0 D*0 B- c c b g g b B+ D0 g g - K+ Heavy Flavor Correlations Isolate b from c Isolate production mechanism In medium: what is losing energy, and how much? Flavor creation  gluon splitting/fragmentation 0 Pusan Colloquium James C Dunlop

  47. Grey Correlations: Heavy Flavor in the fb era Heavy flavor Light Hadrons Identified heavy flavor correlations: promising, but statistical power still low RHIC II: many orders of magnitude (~x1000 with luminosity, S/B improvements) Inclusive Spectra Correlations From 5 pb-1 Pusan Colloquium James C Dunlop

  48. Dh-Df Two-Component Ansatz 3<pt,trigger<4 GeV pt,assoc.>2 GeV Au+Au 0-10% preliminary Simple ansatz • near-side jet peak • near-side ridge • v2 modulated background Pusan Colloquium James C Dunlop

  49. Jet+Ridge ()Jet () Jet) preliminary yield,) Npart Two-component Model at High Pt: “Ridge” and “Jet” 3<pt,trigger<4 GeV pt,assoc.>2 GeV Jörn Putschke, QM2006 Au+Au 0-10% preliminary • “Jet” yield constant • with Npart p+p. low pT Number correlations Au+Au. low pT pT correlations Reminder from pT<2 GeV: h elongated structure already in minbias AuAu f elongation in p-p  to h elongation in AuAu. Dr/√rref STAR, PRC 73, 064907 (2006) Pusan Colloquium James C Dunlop

  50. 200 GeV p+p Gluons vs Quarks: Method • q jets or g jets gluon jet contribution to protons is significantly larger than to pions at high pT in p+p collisions at RHIC; pbar/ < 0.1 from quark jet fragmentation at low beam energy .STAR Collaboration, PLB 637, 161 (2006). • From Kretzer fragmentation function, the g/q jet contribution is similar to AKK. S. Kretzer, PRD 62, 054001 (2000). Pusan Colloquium James C Dunlop