Parton-Medium Interactions via Two Particle Correlations

1. Parton-Medium Interactions via Two Particle Correlations Michael P. McCumber for the PHENIX Collaboration RHIC & AGS Users Meeting 2 June 2009

2. Hard Scattering and Jets Physics Motivation: Jet Reconstruction ■ Energy loss ■ Production geometry ■ Medium excitations = = parton Two Particle Correlation Δϕ, Δη = = Δϕ

3. Pair Correlation Regimes Modification Suppression “intermediate” “high” ≳ 4 GeV/c ~1 - 4 GeV/c

4. Two Source Assumption Pairs correlate via the same hard scattering or via trivial participation in the same event Some correlation sources (HBT, decay) are small Others (recombination) may not be... Background Contribution: ■ collective event shape, v2 ■ normalization, b0 - assume no jet signal at minimum - or calculate combinatorial rate

5. High pT Energy Loss

6. Energy Loss Categories Nuclear Overlap Crossing Nuclear Overlap Tangential

7. Variation with Reaction Plane in out in out The dependence of away-side PTY can discriminate between models.

8. Tangential Rising PTYs Integrated Column Density Trigger Multiplicity in-plane out-of-plane

9. Predicitons: Renk

10. Predicitons: Renk

11. Predictions: Pantuev Vlad Pantuev - nucl-ex/0610002

12. High π0-h± by Reaction Plane Analysis

13. Method Two source model: and rxpn-binning requires: high order

14. Partners 4-5 GeV/c falling away-side trend insignificant near-side trend

15. Partners 3-4 GeV/c same trends as before

16. Away-side ϕS Dependence Both partner bins: ■ Consistent with a linear falling function ■ Steeper than predictions Trend Characterization: ratio of extrema yields

17. Variations by Reaction Plane 4 3 2 1 0 (over-subtraction) falling rising quenched flat

18. “Control” Centrality 0-20% Near-side Away-side Partners: 4-5 GeV/c 3-4 GeV/c No significant trends, nearly complete away-side suppression

19. Away-side pT Spectra • Reaction-plane dependence prefers crossing production • Spectral centrality dependence shows • consistent slopes at high pT • Surviving Partons: • ■ cross the nuclear overlap • ■ lose little energy “skip-through” production indicated for mid-central collisions

20. Summarizing... High pT - Energy Loss Overlap Geometry: ■ possibly more anisotropic than expected in models Surviving partons: ■ cross the overlap ■ lose little energy Intermediate pT - Medium Response But where does the energy go?

21. Intermediate pT Medium Response

22. Near-side Ridge

23. Many Similarities

24. Intermediate pT Triggers

25. Medium Response Triggers Non-fragmentation triggers significantly complicates interpretation Ridge and Shoulder may be: ■ jet-correlated ■ self-correlated Medium Response from the bulk and Recombination effects should be examined

26. Summary High pT - Energy Loss Away-side partons: ■ additional path length = more suppression Surviving partons have: ■ crossed the overlap ■ lost little energy Intermediate pT - Medium Response • Ridge and Shoulder share many properties • and possibly a production mechanism • May not be jet correlated

27. Extra Slides

28. Ridge & Shoulder Balance

29. Jet Functions - Full Set @ 4-5 GeV/c most in-plane most out-of-plane

30. Jet Functions - Full Set @ 3-4 GeV/c most in-plane most out-of-plane

31. Overlays

32. Arb. Scale Definition