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Jet Reconstruction in PHENIX

Jet Reconstruction in PHENIX. Mike McCumber – University of Colorado. & Barbara Jacak – Stony Brook University With thanks to Yue Shi Lai and John Chen. Where does the lost energy go?. We don’t know! Medium enhances gluon radiation/splitting: extra gluons at small

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Jet Reconstruction in PHENIX

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  1. Jet Reconstruction in PHENIX Mike McCumber – University of Colorado & • Barbara Jacak – Stony Brook University With thanks to Yue Shi Lai and John Chen

  2. Where does the lost energy go? • We don’t know! • Medium enhances gluon radiation/splitting: • extra gluons at small • angles (in/near jet cone) • radiated gluons thermalize in medium (i.e. they’re gone!) • remain correlated with leading • parton, but broaden/change jet WWND – PHENIX Jets - Jacak

  3. Leading particles are suppressed Very similar at LHC and RHIC! • Is QGP fully opaque to jets produced deep inside? blue points PHENIX p0 WWND – PHENIX Jets - Jacak

  4. Dijet reaction plane dependence arXiv:1010.1521 p0-h20-60% • Away side is more suppressed out-of-plane • Energy loss is path length dependent • So, medium is not totally opaque!

  5. That’s why we (all) dig deeper • Di-jets • Fragments of energy tagged jets (Justin Franz) • Heavy flavor jet correlations (Anne Sickles) • Full jet reconstruction • To allow us to then deconstruct the jet fragment behavior in QGP John C. H. Chen

  6. WWND – PHENIX Jets - Jacak

  7. s s WWND – PHENIX Jets - Jacak

  8. WWND – PHENIX Jets - Jacak

  9. Goal: see what happens in Au+Au WWND – PHENIX Jets - Jacak

  10. WWND – PHENIX Jets - Jacak

  11. Key issue is event-to-event fluctuations! WWND – PHENIX Jets - Jacak

  12. WWND – PHENIX Jets - Jacak

  13. Fake rejection efficiency effect in p+p? Embedding! WWND – PHENIX Jets - Jacak

  14. WWND – PHENIX Jets - Jacak

  15. WWND – PHENIX Jets - Jacak

  16. Requiring a narrow jet same suppression as leading hadron Hard to reconcile if eloss = splitting inside jet cone WWND – PHENIX Jets - Jacak

  17. Opening filter width finds lost jets?? Not really… WWND – PHENIX Jets - Jacak

  18. Lost energy lurks somewhere nearby? • Broadening, cones/shoulder, ridges, etc? • Search for jet shape modifications • Need different techniques • Look at relatively soft (low-z) fragments • Signal gets tangled up with the bulk WWND – PHENIX Jets - Jacak

  19. Let’s look into differences in v3 2-particle (small Dh) v3 higher than large Dh v3 should expect non-flow contribution i.e. jets WWND – PHENIX Jets - Jacak

  20. Quantify jet-related v3 • Use jets in p+p to calibrate! • Do a Fourier analysis of the per trigger yield jet function • JF = SCncos(nDf) • For Au+Au: combinatorial background “b0(1+2v2trigv2partcos2Df)” removed via ZYAM • NB: absolute normalization yields same results • ZYAM will not change any Fourier coefficients, except C0 and C2 • Various centrality and partner pT bins for initial insights into bulk vs. jet contributions John C. H. Chen

  21. Fourier Spectra of Jet Function v3 from jet+bulk v3 from jet • No significant contribution above c4 • Removing away side jet in pp enhances the codd terms • The C3 in AuAu has contributions from both jet and bulk! John C. H. Chen

  22. Fourier Spectra with high partner pT • Little/no v3 enhancement for high pT partners! • Awayside is suppressed in central collisions • Fourier coefficients agree with “pp-nearside only” John C. H. Chen

  23. Conclusions • QGP is very, but not fully opaque to jets • punch-thru at pT>3 GeV: energy not thermalized • Reconstructed jets suppressed as leading hadrons • But what’s in a jet? • Holds for relatively narrow Gaussians/cones • How to find/reconstruct a modified jet? • Gluon splitting puts energy outside normal jet fragmentation zone • g-jet correlations show evidence for low-zhadron enhancement • Messes up normal jet finding, shape must change! • Fourier analysis shows v3 = bulk + jet contributions • The devil (and shape info) is in the details • Let’s get the details right! WWND – PHENIX Jets - Jacak

  24. Backup WWND – PHENIX Jets - Jacak

  25. WWND – PHENIX Jets - Jacak

  26. sPHENIX Upgrade Concept + one existing Muon Arm w/ a new absorber 2T mid-y magnet, I.d.~ 60cm (could be up to ~ 1m) Compact EMCal E/E ~ 20%/√E (Si/W & Scint/W?) Intermediate tracker ~80 resolution (GEM or Si) Compact HCAL for jet reco (first HCAL at RHIC!) Forward spectrometer optimized for electrons, , hadrons Hadron ID: forward yes, mid-y ? WWND – PHENIX Jets - Jacak

  27. HCAL: unique jet capability at RHIC • HCAL energy requirement removes sensitivity to fake high pT tracks • Modest HCAL segmentation ( = 0.1) and resolution E/E ~ 45% WWND – PHENIX Jets - Jacak

  28. + DAQ/Trigger: 50B events! sPHENIX Upgrade Concept WWND – PHENIX Jets - Jacak

  29. sPHENIX physics reach quarkonia Jets, photons 50B events! WWND – PHENIX Jets - Jacak

  30. vn from two particle correlations • Standard: v2(v4): single particle vs. reaction plane dN/d(f-y) • Can also measure vn via two particle correlation • PHENIX: Phys. Rev. Lett. 89, 212301 (2002) • dNAB/df = N(1+ S(2Cncos(nDf))), Cn = vnAvnB • the two particles are in the same event, therefore share the same reaction plane • When pTA = pTB, vn = sqrt(Cn) • With low partner pT (below 1 GeV), the jet contribution can be ignored, but not at high pT John C. H. Chen

  31. v2, v3 from two particle correlations • v2 agrees with previous PHENIX measurements at low pT • v3 • Nonzero • Increases with pT (NB: may have non-flow effects in this method) • Increases with centrality John C. H. Chen

  32. WWND – PHENIX Jets - Jacak

  33. If you find the jets, they’re pretty normal WWND – PHENIX Jets - Jacak

  34. WWND – PHENIX Jets - Jacak

  35. RHIC and LHC • Energy dependence is a key tool for understanding • RHIC provides a sweet spot for • Strong coupling; dialing medium properties/ baseline • Rapidity range selecting importance of initial state • Dominated by quark jets, access 15<ET,jet<60 GeV • Sampling large luminosity with min bias trigger WWND – PHENIX Jets - Jacak

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