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Résultats récents du RHIC

Résultats récents du RHIC. Outline : (1) heavy quarkonia production; (2) jet – medium interactions in heavy ion collisions; (3) correlations and fluctuations; (4) forward and central flow; (5) searching for gluon saturation;

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Résultats récents du RHIC

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  1. Résultats récents du RHIC Outline : (1) heavy quarkonia production; (2) jet – medium interactions in heavy ion collisions; (3) correlations and fluctuations; (4) forward and central flow; (5) searching for gluon saturation; (6) W/Z measurements. Guy Roche, LPC-Clermont. Etretat, 20-23 Septembre 2010. p.1

  2. 1) heavy quarkonia production. From Daniel Kikota for the STAR colaboration, ICHEP 2010. baseline:  in p+p 200 GeV Consistent with CEM, (inconsistent with CSM: ~ 2) Consistent with world data trend p.2

  3. Cold nucl. matter:  in d+Au Cold nucl. matter:  in d+Au Consistent with Nbin scaling. Cold Nuclear Matter effects (shadowing) are rather small. p.3

  4.  in Au+Au 200 GeV 4.6 significance, 95 Signal counts in 8 < m < 11 GeV/c2 Includes , Drell-Yan + bb Analysis in progress p.4

  5. Summary • High-pT J/ψmeasurement in p+p - a crucial test of quarkonia production in QCD. •  (B  J/ψ / J/ψ = (13 ± 5)% for pT > 5 GeV/c. • No J/ψ suppression at high-pT in Cu+Cu 200GeV: RAA ~ 1 •  First  cross section measurements at RHIC energies: • - p+p results consistent with Color Evaporation Model • - d+Au: RdAu = 0.78 ± 0.28 (stat.) ± 0.20 (sys.) p.5

  6. (2) jet – medium interactions in heavy ion Collisions. From Olga Evdokimov for the STAR colaboration, ICHEP 2010. Angular pair-correlations 84-93% 74-84% 64-74% 55-64% 46-55% proton-proton 18-28% 28-38% 9-18% 5-9% 0-5% φΔ ηΔ STAR Preliminary Evolution of several correlation structures is observed Shown are 200 GeV minimum bias Au+Au data. Similar analysis performed for 200 GeV Cu+Cu, and 62 GeV Au+Au and Cu+Cu data. p.6

  7. assoc. trig2 trig1 Di-jets through correlations Trig1 is highest pT particle in event with 5-10 GeV/c Trig2 (pT > 4 GeV/c) is back-to-back with Trig1 Associated particles pT > 1.5 GeV/c. 200 GeV Au+Au and d+Au. same-side away-side associated particle pT spectra STAR Preliminary • No evidence of medium modifications Di-jets observed - all tangential? p.7

  8. Jet-energy calibrarion Direct γ-hadron correlations STAR Preliminary • Similar medium effect on the away-side of 0 and dir •  is this due to tangential emission? • rich sample has lower near-side • yields compared to those of the • 0 different bias p.8

  9. Inclusive jet measurements Central Au+Au: background correction leads to a factor of 2 uncertainty in cross-section p.9

  10. 3) Correlations and fluctuations. From Terence J Tarnowsky for the STAR collaboration, Winter Workshop on Nuclear Dynamics 2010. F-B Multiplicity Correlations • Predicted in context of Dual Parton Model [DPM] (and Color Glass Condensate [CGC]). • Test of multiple elementary [partonic] scattering. • Linear expression relating Nb and Nf (forward and backward multiplicity), found in hadron-hadron experiments (ex. UA5), • “b” is correlation strength. • Function of √s and A. • Coefficient can be expressed as, N = # of hadrons p.10

  11. F-B Correlations • Central 200 GeV Au+Au collisions show a strong long-range correlation. • Most peripheral Au+Au have negligible LRC, as does pp. • HIJING and Parton String Model (PSM) do not agree w/ Au+Au data. • Multiparton interaction in central Au+Au collisions. • See talk by M. Skoby. Phys.Rev.Lett.103:172301,2009 p.11

  12. Characterize Fluctuations • NA49 uses the variable dyn • Measure deviation from Poisson behavior using dyn • It has been demonstrated (for K/p and p/p) that, p.12

  13. Excitation Function for σdyn,K/π STAR central Au+Au (0-5%) collisions with SPS central Pb+Pb collisions (0-3.5%). Phys.Rev.Lett.103:092301,2009 • Large decrease in fluctuations as function of energy from NA49. • Fluctuations measured by STAR approximately constant as function of energy from 19.6-200 GeV. • p : 0.2 < pT < 0.6 GeV/c • K: 0.2 < pT < 0.6 GeV/c p.13

  14. 4) Forward and central flow. From Eric Richarson for the PHENIX collaboration, RHIC & AGS Annual Users Meeting June 7-11, 2010 BNL. • RP detectors with different  ranges yield similar signal • Signal varies v2 (v4) • mid-central ~5% (10%) • central/peripheral 10% (20%) • Signals agree within systematic errors (v2 = 10%, v4 = 20%) • Indicates reliable measurement largely free of  and pT dependent non-flow effects within the measured range (pT = 0.5 - 2.4 GeV/c) v2, v4 h± Results arXiv:1003.5586 p.14

  15. 0-60% Centrality v2, v4 h± Results • Fig (a) & (b) • v2 and v4 signal have similar shape • Fig (c) - v4/(v2)2 • Ratio independent of pT within 0.5-3.6 GeV/c • v4/(v2)2 ≈ 0.8 for ~50<Npart<200, which is greater than ideal hydro (dot-dot) • adding eccentricity fluctuations within hydro model fits data better (dash-dash) • Even better fit when  added to hadron gas phase and small  added to QGP phase (dot-dash) • Ratio significantly increases Npart > ~200 • Additional fluctuations needed to match central data (solid) • Fit with data implies a small /s Data gives strong indication of hydrodynamic behavior in matter created at RHIC These precision measurements should provide stringent constraints for models. p.15

  16. Heavy Flavor v2 Analysis Footnotes arXiv:1005.1627 • Run-4, ~700M evts • Measured heavy flavor using single electrons from semileptonic decays (~10% branching ratio) • Tracking done using DC, PC, RICH and EMCal • RICH is primary electron identifier • Photonic electron bkgrd subtracted using “cocktail method” where background v2 was estimated using a Monte Carlo simulation with input from measured data • Photonic cocktail included electrons from 0 and  decays and  conversions and direct  • Electron v2 from K decays was also subtracted arXiv:1005.1627 p.16

  17. Heavy Flavor v2 Results • Positive v2 at low pT - indicates heavy quarks (mainly charm) couple with the medium. • Shape similar to lighter quarks except at highest pT. • Although errors are large at high pT the signal appears to fall significantly from peak. This indicates a change in energy loss mechanism or a growing contribution from the bottom quark. arXiv:1005.1627 p.17

  18. Model Comparisons • All models include quark coalescence • Models that best describe low pT data are: • Greco et al. with charm flow • Zhang et al. with larger charm quark parton-scattering cross section ( = 10 mb) • van Hees et al. with resonance interactions • Indicates • heavy quarks participate in the medium • Coalescence and resonance are large contributors to HF v2 at low pT arXiv:1005.1627 p.18

  19. 5) searching for gluon saturation. From Beau Meredith for the PHENIX collaboration, DIS Conference, Florence, Italy, April 19-23, 2010. Rapidity Separated Correlations : Widths. 2.0 < pT,trig< 3.0 GeV/c trigp0or h+/-, h = 0 assoc p0, h = 3.4 No significant broadening between p+p and d+Au within large experimental uncertainties p.19

  20. Rapidity Separated Correlations : IdA . 0.45 < pT,assoc < 1.59 GeV/c trigp0or h+/-, h = 0 assoc p0, h = 3.4 Increasing suppression of IdA reaches a factor 2 for central events indicating di-jet suppression peripheral central p.20

  21. Forward/Forward Correlations : p+p . • Show per-trigger correlation functions, i.e. 1/NtrigdN/d(Df) • Area of away-side peak represents conditional yield without efficiency correction • More work needed to determine uncorrelated background level • Conditional yields, widths not shown Trigger particle pT > 2 GeV/c Associate particle pT > 0.875 GeV/c Data points mirrored for Df > p trigclusterh = 3.4 assoc p0, h = 3.4 p.21

  22. p+p vs d+Au Central . Decorrelation and/or suppression seem to get stronger for central d+Au collisions. p.22

  23. p+p vs d+Au Peripheral . Peripheral d+Au collisions are more similar to p+p collisions p.23

  24. + - 6) W/Z measurements. From Mickey Chiu for the PHENIX collaboration, RHIC and AGS Users Meeting, June 7-11, 2010. Comparison To Measured spectra Data and MC driven BG estimation: EMCal cluster distribution after subtracting cosmic background  (Conversion + Accidental)  Tracking Acceptance • (NLO Hadrons thru Geant + FONLL c/b) • Normalization from fit to 10-20 GeV + • The same scale factor for PYTHIA was used for W/Z shape. • W-e- signal has fewer counts than W+e+ signal as expected p.24

  25. Isolation cut • Signature of a W event is that it is isolated • Sum up energy in a cone around electron and in cone on opposite hemisphere E < 2GeV + - • 90+% of signal is kept (red histograms) • Factor ~5 reduction in jet dominated region p.25

  26. STAR Preliminary Run 9 From Joe Seele for the STAR collaboration, RIKEN BNL Research Center Workshop, June 24-25, 2010. 2009 Results In 2009 STAR recorded its first 500 GeV data set and extracted its first mid-rapidity AL measurement. Achieved S/B~11 for the W+ and S/B~6 for W- p.26

  27. Expected Data RHIC is planning to run 500 GeV polarized p+p collisions in a multi-year effort to constrain the polarization of the anti-quarks in the proton Calculations assume the demonstrated S/B (6 and 11) for the mid-rapidity projections and S/B~1 for the forward and backward rapidity projections p.27

  28. Back-up slides p.28

  29. Summary &Outlook from STAR: • Jet quenching discovered at RHIC has been extensively studied for years: • Modification of angular shapes, production rates, transverse momentum and energy distributions • Evolution of jet studies in HI: • Inclusive hadron measurements → di-hadron correlations → multi-particle correlations → full jets • Outlook: • Towards “theory-ready” (partonic) energy loss measurements • Disentangling experimental biases p.29

  30. ndyn,p/p, STAR and NA49 • ndyn,p/pdisplays strong system size dependence for small dN/dh. • Fit is to STAR Cu+Cu 22.4 GeV data only. • Interpretation still under study. p.30

  31. Inclusive jet ratios R=0.4 RAAJet RAA of pions ~ 0.2 RAAJet> RAAp: recover larger fraction of cross-section, but not all Significant ratio suppression wrt. pp → medium induced ET broadening p.31

  32. Excitation Function for σdyn,p/π • Solid points are data from STAR or NA49. • Open black points are HSD prediction from Konchakovski, et. al. arXiv:0906.3229. • Open red points are UrQMD run locally with STAR acceptance. p.32

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