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Dihadron Correlations in Heavy Ion Collisions

Dihadron Correlations in Heavy Ion Collisions. Michael P. McCumber Nuclear Physics Summer Seminar Stony Brook, NY. Heavy Ion Collisions. Jet Suppression: Fast partons lose energy in the medium Lost energy should be deposited locally in the medium. Where does the energy go?

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Dihadron Correlations in Heavy Ion Collisions

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  1. Dihadron Correlations in Heavy Ion Collisions Michael P. McCumber Nuclear Physics Summer Seminar Stony Brook, NY

  2. Heavy Ion Collisions Jet Suppression: Fast partons lose energy in the medium Lost energy should be deposited locally in the medium Where does the energy go? Does anything of the jets remain? Does the lost jet energy elicit a response from the medium? ? Michael P. McCumber

  3. Away-side Jet Correlations p-p collisions: ● Pair yield near Δφ=0 and Δφ=π ● Back-to-back jet scenario p+p 200 GeV nucl-ex/0611019 Central Heavy Ion Collisions: ● Requires significant subtraction of combinatoric event correlations (elliptic flow) ● Pair yield near Δφ=0 and Δφ≈2 PRC 73, 054903 (2006) Michael P. McCumber

  4. PHENIX Detector Central Arms |η| < 0.35 Charged tracking from DC, PC1, and PC3 at mid rapidity, η. Centrality and Reaction-plane from BBC and ZDC at large |η|. “trigger hadron” (2.5-4.0 GeV/c) “partner hadron” (1.0-2.5 GeV/c) Beam View Michael P. McCumber

  5. Acceptance Correction B A Event N Rolling buffer mixing technique Pooled by Event type: 5cm zvertex 5% centrality B Event N-1 A Event N-2 A B A B Event N-3 A B Event N-4 Acc(Δφ) The two-arm acceptance effects are removed by building a correction from event mixing. π 0 ΔΦAB Michael P. McCumber

  6. Dihadron Correlations Metrics: Shape Yields Conditional Spectra … Example Cu+Cu 62.4 GeV h-h correlation Dials: Beam Energy Beam Species Centrality Transverse Momentum Reaction-Plane Orientation … Michael P. McCumber

  7. Inclusive Correlations Additional Measurements: v2: Observed v2 Rx-pn Resolution b0: Flow Normalizations Measured Correlation function includes both jet-induced and flow terms Michael P. McCumber

  8. Measuring Elliptic Flow, v2 Mean Projection: Rx-pn  Track Fit: Michael P. McCumber

  9. Measuring Reaction-Plane Resolution, Δ Mean Projection: Rx-pn  Rx-pn Ollitrault-Voloshin: Michael P. McCumber

  10. Flow Normalization, b0 Correlation & Flow Functions ZYAM assumes the existence of negligible jet-like yield in some region Fit method assumes a double-Gaussian away-side shape Absolute method calculates the expected background from the singles multiplicity, but requires a sometimes substantial correction due to centrality multiplicity correlations and a small correction for pair-cut efficiency Determine the flow normalization, b0, from three methods: ZYAM Method Absolute Method Fit Method Michael P. McCumber

  11. Mult. Correlation Corrections, ξ NA x NB NB bin N NA The multiplicity has a correlated centrality dependence within the bin Increasing Centrality → ξ largest in peripheral where N vary the most across a bin. Michael P. McCumber

  12. Pair CutCorrection, Κ The background must be treated identically to the foreground. Therefore, there must be some pair multiplicity lost to the pair cuts in each. This is the purpose of the Κ correction. B B A A B B B B A A B B K, the survival probability, is typically ~99.3% and can be estimated in mixed events Michael P. McCumber

  13. Comparative Normalizations Michael P. McCumber

  14. Analysis Walk-Through Correlation, Flow & Jet Functions Done! Michael P. McCumber

  15. Beam Energy & System Scan Away-side structure vs. beam species, beam energies, and centrality All cases: ● Peripheral similar to p-p ● Central shows development of “lobe”-like structure Phys. Rev. Lett. 98, 232302 (2007) Michael P. McCumber

  16. Beam Energy 17.2 GeV 62.4 GeV 200 GeV Now can see first significant sign of an away-side beam energy shape dependence Our own future energy scans and possible LHC results will add to this story Michael P. McCumber

  17. Away-side Shape Metrics Model-Independent: J(Δφ) Model-Dependent: Michael P. McCumber

  18. SystemSize Common trend with system size Transition region between 0 and 100 Npart Shape saturates above 100 Npart No observed energy dependence Phys. Rev. Lett. 98, 232302 (2007) Michael P. McCumber

  19. Transverse Momentum, pT Away-side ‘cone’ is seen in all intermediate pT correlations Position of intermediate pT away-side insensitive to trigger pT Normal, but suppressed, away-side at high pT arXiv:0705.328v1 Michael P. McCumber

  20. Transverse Momentum, pT Away-side shoulder <pT> is insensitive to trigger pT (above 100 Npart) arXiv:0705.328v1 Michael P. McCumber

  21. Experimental Summary Away-side shape scaling with Npart Shape saturation above 100 Npart This away-side shape is a ubiquitous feature of intermediate pT jet-like correlations in mid-central and central heavy ion collisions The spectrum shape under the away-side peak and peak location are insensitive to trigger pTabove 100 Npart Michael P. McCumber

  22. Large Angle Scattering -- Vitev Angles are typically smaller than observed Average scattering angle falls with path length Contrasts our centrality dependence hep-ph/0501255 Michael P. McCumber

  23. Large Angle Scattering – Polosa, Salgado PRC 75, 041901(R) (2007) Claim that the similar pT windows restrict signal to a small number of splittings Michael P. McCumber

  24. Mach Cones θM = 1.2 → cs ~ 0.33 (0.57 in QGP, 0.2 in hadron gas) D ~ 1.0-1.1 → cs ~ 0.45 - 0.54 Casalderray,Shuryak,Teaney hep-ph/0411315 Stöcker, Nucl. Phys. A750 (2005) 121 Reproduces large angles seen in the data Expectation of little pT dependence Expectation of a beam energy dependence Michael P. McCumber

  25. Mach Cones – Jorge & Edward First-order phase transition would reflect some Mach Cone hep-ph/0511263 Michael P. McCumber

  26. Mach Cones – Renk & Ruppert HP 2006 Longitudinal flow improves the predicted Δφ signal from a Mach Cone Match to the data requires large fractional energy loss to Mach cone Away Near→ Michael P. McCumber

  27. Mach Cones – Chaudhuri & Heinz PRL 97, 062301 (2006) Assume lost energy is instantaneously thermalized in their hydro simulations Extract no Mach cone signal Large energy loss scenarios give “splash-back” signal Michael P. McCumber

  28. Cherenkov – Majumder, Wang Cherenkov production has “a strong dependence on the gluon momentum” “disappear for high-energy gluons” Predict D values will shrink as associated momentum is increased. PHENIX Phys. Rev. Lett. 98, 232302 (2007) PRL 96, 172302 (2006) Michael P. McCumber

  29. What is so special about Npart? Phys. Rev. Lett. 98, 232302 (2007) Michael P. McCumber

  30. Reaction-Plane Orientation thicker via trigger to reaction plane selection out mid in peripheral central thicker via centrality selection Cu+Cu Au+Au Michael P. McCumber

  31. Correlation Functions Michael P. McCumber

  32. Au+Au 200 GeV – Cent 30-40% Correlation Decomposition: Bielcikova, Esumi, Filimonov, Voloshin,& Wurm PRC69 (2004) 0211901 (QM 2005) Correlation Decomposition: The inclusive distributions vary greatly with Ψ-φ bin due to large changes in the flow contribution. The in-plane & out-plane JFs show no rxpn-dependence within the reported errors. Bielcikova, Esumi, Filimonov, Voloshin,& Wurm PRC69 (2004) 0211901 Michael P. McCumber

  33. Why Cu+Cu? If the Npart scaling is in fact related to the geometrical thickness through the medium, we should also see a dependence on line-of-sight through the medium. Need a small system to probe transition region, Cu+Cu is ideal in this regard. Au+Au 30-40% Cu+Cu Increasing Thickness? Michael P. McCumber

  34. Cu+Cu 200 GeV Jet Functions: Large dependence with centrality No observed dependence in jet functions with reaction-plane Michael P. McCumber

  35. Jet Contribution Errors Large, correlated (sometimes anti-correlated!) systematic errors Given a particular centrality, only φs changes with rx-pn bin Michael P. McCumber

  36. Shape Metrics by Npart Same Npart trend as previously measured. No observed difference between reaction plane bins Michael P. McCumber

  37. Geometrical Thickness Distant Observer trms = 2 Rrms freq. 0 R-<R> trms is a typical radial thickness along lines of sight from within a reaction-plane bin Includes reaction-plane resolution Overlapping Wood-Saxon Distributions Michael P. McCumber

  38. Shape Metrics by trms Overall trend as expected from Npart dependence. Too little sensitivity to reaction-plane binning Michael P. McCumber

  39. STAR Result Centrality 20-60%, STAR has better rxpn resolution (Δ=0.7) but also non-flow effects Data shows a dependence to the away-side AND the near-side (APS April 2007) Michael P. McCumber

  40. Final Summary No observed reaction-plane shape dependence Unable to differentiate: no thickness scaling expected thickness scaling from centrality variation New Reaction-Plane Detector Better resolution Better flow systematic errors Michael P. McCumber

  41. In the Future for Correlations Michael P. McCumber

  42. Supporting Slides

  43. Correlation Functions Michael P. McCumber

  44. Flow Functions Michael P. McCumber

  45. Shape Metrics by trms Overall trend as expected from Npart dependence. The current poor reaction-plane resolution does not give sufficient thickness sensitivity to distinguish between no reaction-plane dependence and the expectation from the centrality dependence. Michael P. McCumber

  46. Transverse Momentum, pT PHENIX Preliminary Michael P. McCumber

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