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Probing RHIC Matter with High pT Spectra and Correlations of Jets with Other Probes

This talk covers the latest results from high pT hadron spectra, comments on energy loss difference between quarks and gluons, direct photon high pT spectra, and direct photon-jet correlations at RHIC. It also discusses the role of shadowing and energy and system size studies.

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Probing RHIC Matter with High pT Spectra and Correlations of Jets with Other Probes

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  1. Probing RHIC Matter with High pT Spectra and Correlations of Jets w/ Other (non-Jet!) Probes Justin Frantz SUNY Stony Brook ISMD 2007 08/08/07 Thanks to the organizers!

  2. Outline • “Garbage Collection” talk (not garbage – everything not covered elsewhere?) • Latest Results from high pT Hadron Spectra • Lower energy suppression data • Comments on Eloss diff btw q/g (color factor) • ...in relation to PHENIX search for Jet-Medium g • Direct photon high pT spectra • New lower energy direct photon • Direct photon-jet correlations at RHIC • A slide on STAR heavy flavor – jet correlation measurement Oscar the Grouch Justin Frantz - ISMD ‘07

  3. Argh... these plots again? Reminder: Raa = A+A / Nscaling*p+p YES! we see high pt suppression! Justin Frantz - ISMD ‘07

  4. OK, use it constrain theory parameters • QM’06: fitting analysis • Latest (last couple weeks) re-analysis confirms qhat not well constrained esp. on high side • Soon to be published, along with finalized p0 spectra Model values from C.Loizides hep-ph/0608133v2 Justin Frantz - ISMD ‘07

  5. Wait? Is that it? • No... my feeling is that we say “RAA is fragile, NEXT...” • RAA vs pT != All Spectra Measurements • Stil a lot of interesting results in the high pT single particle rates... • What’s new? Lot’s of stuff... • New Questions arising: e.g. role of shadowing– (direct photon data) ? • Energy, system size studies being somewhat forgotton now? (by Theory and Experiment) Refresh our memory and look at some new developments Justin Frantz - ISMD ‘07

  6. Substantial change still large sys errors (change ~covered) – errors too big? How do (other) Eloss calc’s compare vs Energy Old RAA used reference from fit of many disagreeing datasets New measured Run5 p+p reference my approximate eye guides New 62.4 GeV RAA Updated STAR p+p ref underway Justin Frantz - ISMD ‘07

  7. Two Energies • Can we (simultaneously?) fit both energies within one model? • Quantify more details of other Eloss ingredients • If final relative systematics are too big, more cleverly cancel Glauber systematics ? • Combinations of RAA and RCP? STAR Prelim h 62.4 200 Reminder: Rcp = A+Acentral / Xscaling*A+Aperipheral Justin Frantz - ISMD ‘07

  8. Energy Loss Models: Ingredients • Different models have dependence on various ingredients which should vary as fn of s • e.g. Energy Density... • ...Dynamic medium motion, Temperature, Initial state effects... Nuclear Physics A Volume 757, Issues 1-2 , 8 August 2005, Pages 184-283 From PHENIX White Paper... Justin Frantz - ISMD ‘07

  9. Much lower (SPS!) Energy... • Recent PHENIX Result for √sNN 22 GeV Cu+Cu. STAR data also iminent • Same fitting for p+p ref, but 22 GeV fit more reliable • Eloss models Cronin fits this data? Justin Frantz - ISMD ‘07

  10. Ncoll,Pb+Pb = 807 ± 81 preliminary Or even Eloss -- there is some? • Recent SPS result shows suppression if compared to Cronin enhanced p+A (fake “Raa”) • But Cronin scaling w/ Ncoll can’t be trusted quantitatively • Interesting: if we make same ratio in RHIC 200, we’d see 20 % less suppression (shadowing influence) PHENIX 200 GeV p0 Point: should be trying to understand these non-Eloss suppression influences more quantitatively! Justin Frantz - ISMD ‘07

  11. System Size or Centrality Dep? • First look: same suppression behavior vs system size... • Need to verify whether this holds up under final errors/analyses • e.g. PHENIX points hint to be non-scaling? pT>6 GeV/c Justin Frantz - ISMD ‘07

  12. ~New Q: Color Charge Dep: q vs g? • B. Mohanty talk Monday: • Recent AAK Frag fn. set including STAR data: protons from glue frag (hep-ph/0702250) • Should see different suppression for protons/pions • Not seen in data? (Within errors) STAR Justin Frantz - ISMD ‘07

  13. Color Charge Dep: q vs g? • Caveats • Frag fn fits have large uncertainty • Inclusion of all ingredients (expansion, time) dependence can reduce the effects in real Eloss models? (e.g. Vitev PLB 639 (2006) 38) • qg/gq Conversion in the medium? • Liu, Ko (nucl-th/0607047) • I want to point out a constraint that already exists gp FF hep-ph/0702250 Justin Frantz - ISMD ‘07

  14. q/gg/q Conversion Calculations As jets traverse the medium their q/g identity is blurred--conversion Factors of 4-6 enhancement of Conversion rates required to explain Justin Frantz - ISMD ‘07

  15. Constraint: Medium Induced Gamma • These q/g conversion calc’s are very similar to another calculation: • “Direct” Photon medium enhancement in 4-6 GeV/c pT range • Basic jet parton (q/g) on medium q/g “targets” cross sections from NLO • Folded with thermal distribution of medium For photons: “Canary” effect from n talk yesterday (Barwick): intrinsically small rate for photon production means sizable addition even if small effect for jets Justin Frantz - ISMD ‘07

  16. “Jet-Medium” Photons • Jet to g Conversion • Model: q jets traversing q/g bath convert (Kinematics: small u dominates: pg ≈ pq) First calc Fries, et. al./ more complete treatment w/ Turbide,Gale et. al. (hep-ph/0508201) • Fragmentation / Bremstrahlung g • Jet Eloss implies suppression of Frag g but Zakarov (hep-ph/0405101) • /others predict enhancement Direct g w/o suppresion Justin Frantz - ISMD ‘07

  17. Jet-medium Enhancement Tested… • At mid pT enhancement predictions disfavored (ETD-HIC ~2 wks ago statement: can be made consistent) • However, factor of 4 ruled out? • Q’s about nature of the medium/ radiative Eloss? • At high pT data favors standard suppression predictions, not enhancement Justin Frantz - ISMD ‘07

  18. Direct Photon v2 • Jet suppression should cause same v2 for normal frag as for h • Enhancements should have negative v2 • Not seen in the data... Turbide, et.al Check w/ more scrutiny for finalization: odd suppression pattern vs cent.? PHENIX Preliminary PHENIX Preliminary Justin Frantz - ISMD ‘07

  19. Color factorvs Reaction Plane? • Suggestion: look at proton ratios as a function of reaction plane • Shed some light on color factor question? • e.g. if q/g conversion phenomena exists/is important, it should be path length dependent in the same way as for Jet Medium g... Reminder: Reaction Plane = measurable A+A event plane Justin Frantz - ISMD ‘07

  20. Reaction Plane (RP) Dependence • v2 @ high pT:  RP Dependence of Eloss • Physics: Study More Pathlength Dependence Many Measurements of high pT v2/Raa or “Raa vs RP” • v2 focus has been low pt hydro regime • Need to study high pt, together with theory (several predictions: Majumder et al, Renk et al.) • Improved precision needed in data Renk et. al. nucl-th/0611027 Justin Frantz - ISMD ‘07

  21. Direct Gamma @ high pT • Considerable interest in high pT behavior • Shadowing/Isospin effect? (predicted by Arleo (JHEP 0609 015 (2005)) • Questions of Initial State, shadowing effects in general for A+A • Recent global re-analysis of nuclear PDF’s • Impact parameter (cent.) dependent nuclear PDF’s? • New measurement of 62.4 GeV Au+Au Direct g • Consistent w/ Binary Scaled NLO Justin Frantz - ISMD ‘07

  22. xT scaling • Lower pT, 62.4 GeV data ~same xT as 200 GeV • p+p ref spectra follow xT scaling • Comparison hints that shadow/Init. State effect present NLO Direct g Spectra pT xT Justin Frantz - ISMD ‘07

  23. Heavy quark Eloss will be discussed tomorrow Same as light q/g? 2-particle correlation method being applied Main point so far: c/b separation (fit nearside) What about awayside IAA? Future: study associated jet in A+A Charm, Heavy Q? Suppression p+p Justin Frantz - ISMD ‘07

  24. g-jet @ RHIC • Cleaner determination of fragmentation modification (Eg == Ejetorig)~ better constrain Eloss models IAA of Awayside yield of Direct g triggers F. Arleo hep-ph/0601075 IAA Renk.. hep-ph/0607166 w/ Eloss Trigger g don’t have same surface bias, thus should help constrain Eloss geometry Justin Frantz - ISMD ‘07

  25. RHIC g-Jet Methods Statistical Subtraction w/ 2-p Df Correlations (remove meson decay contribution to inclusive photon corr) PHENIX Au+Au 200 GeV PHENIX: Rg incorporate PHENIX Direct g Rg measurement STAR: Use Shower Shape discrimination + p0 measurement Assume NearSide direct yield = 0  direct fraction from NS reduction Justin Frantz - ISMD ‘07

  26. g-jet First Results: PHENIX • PHENIX Au+Au compared to p+p • Cu+Cu now available • Run 7 Statistics on Tape: ~3x • + use p0/decay g as associated: another x 2 • IAA should be possible + other improvements Justin Frantz - ISMD ‘07

  27. g-jet First Results: STAR • Integrated Away-side yields: • STAR/PHENIX p+p yields consistent (STAR trigger bin higher) • PHENIX Au+Au consistent with expected suppression p+p Justin Frantz - ISMD ‘07

  28. Finalizing the Result: h decay (h-h) • Systematic from h contribution • PYTHIA difference in h/p frag surprising (more than mT) • Data measurement performed! • First h-h measurement @ RHIC Daughter-h • Parent-h p+p Justin Frantz - ISMD ‘07

  29. Run 5 p+p @ 200 GeV Statistical Subtraction Method p0 Direct g Recent Improvements in p+p w/ more stats, eta measured, multiple trigger bins • Slope difference ~ promising. Diff. sensitivity to frag etc. • “Tagged” quark jets: Difference btw glue and quark jets? (plenty of other reasons of course) • ... more in search for the color factor (g vs q) in Eloss Justin Frantz - ISMD ‘07

  30. Using Tagged Quark Jets (to come) Under construction • More information in this direction: • Check conclusion that “all baryons are from glue jets” • STAR method can accomodate this measurement nicely also—more associated pT coverage than PHENIX Direct g pt 5-7 GeV/c pTa 1-2 GeV/c (prompt) PHENIX Justin Frantz - ISMD ‘07

  31. Summary of Main Points • There is still life left in high pT spectra! • New energy dep. data can contrain Eloss models and/or their “ingredients” : let’s not forget about this! • Color factor q vs. g Eloss diff interesting question (?) • Ideas for q/g conversion already constrained by intermediate pt direct photon yield • Direct photon spectrum hinting at some A+A modification • shadowing/isospin effect supported by new 62.4 GeV data? • Highlights better understanding of initial state effects even in hadron suppression • Direct Photon-Jet and Heavy q-Jet Correlation measurements underway • First measurements of both A+A consistent w/ expected suppression of g-jet pairs • Improvements in p+p and Run7 A+A should improve observation of A+A suppression of g-jet pairs • Also allow quark jet “tag” Justin Frantz - ISMD ‘07

  32. Backup Justin Frantz - ISMD ‘07

  33. Scan: Shape Study • With these, do systematic study of shape • rms, kur (4th moment, non-gaussianness), peak location D Use Fit w/ allowing Away Peak Fit D PHENIX Fix D Away Width PHENIX Work In Progress Justin Frantz - ISMD ‘07

  34. pT Dependence of shape • Most interesting feature, here again is constant D PHENIX PHENIX Final This is expected in some “Mach Cone” explanations, but inconsistent with initial color Cerenkov cone model... Justin Frantz - ISMD ‘07

  35. pT Dep. of Shape and Yields Detailed study of pT dep. in central Au+Au PHENIX HS Ratio allows one to see where cone appears and “disappears” Justin Frantz - ISMD ‘07

  36. pT Dependence of Yields • Calculate slope of the yields in each region • S region: harder than bulk • New interpretation: H region harder than shoulder until quenched—then dominated by tails of S or bulk • H region centrality dependence much like inclusive high pT suppression Inclusive h pT trig Centrality Justin Frantz - ISMD ‘07

  37. 0-20% 2.5-4x1.6-2 GeV/c Cone Chemistry • Triggering on high pT and identify the associated hadrons • Cone shape observed baryons/mesons both (slight differences?) • B/M Ratio btw bulk and jet Justin Frantz - ISMD ‘07

  38. Au+Au RP Dependence • Is there any “path-length”, direction (wrt RP) dependence? • Seems to be small, or hidden w/ RP reso. Justin Frantz - ISMD ‘07

  39. Cu+Cu RP Dependence • Cu+Cu same Deccentricity in smaller Npart range (also range where cone could be distorting/disappearing) • Still no major difference seen • could still be RP resolution, even worse in Cu+Cu • New RP detector in Run 7 Au+Au PHENIX Work in Progress Stony Brook Analysis (M. McCumber and JF) Justin Frantz - ISMD ‘07

  40. Conclusions so far about the Cone • Exists in ~all systems/ “hot medium” energies (including SPS!) and systems • shape independent of centrality • pT dependence is rich in physics: • Cone location is ~independent of pt • Slope of cone assoc. pt dependence of associated is like slightly harder than bulk, independent of trigger pt, ~centrality • not shown (WIP): cone yield at fix assoc pt, weakly rises w/ trigger pt, slower than p+p jet • B/M Ratio of Cone is lower than bulk, higher than pure jet These are consistent w/ some Mach Cone expectations Looking like jet-related medium excitation! Justin Frantz - ISMD ‘07

  41. Jeon, Jalilian-Marian, Sarcevic nucl-th/0208012 Switching Gears (a little) • Picture of direct photons being unmodified not completely valid especially at lower pt • First gdirect porton from Fragmentation/ Bremstrahlung  from jets ie suppressed • However in addition, enhancement due to analagous mechanisms of the quenching jet-medium interactions • Multiple Scattering (Collisions) • Radiation Another type of Jet-Medium Interaction Signal! Justin Frantz - ISMD ‘07

  42. Jet-Medium Photons • g-jet Conversion • Model: q jets traversing q/g bath convert (Kinematics: small u dominates: pg ≈ pq) First calc Fries, et. al./ more complete treatment w/ Turbide,Gale et. al. • Fragmentation (Brems.) g • Jet Eloss implies suppression of Frag g but Zakarov/others predict enhancement (New paper from E. Wang et. al.) also included by the above authors. w/o suppresion Justin Frantz - ISMD ‘07

  43. Implications/Discussion • Homework for theory: • Bremstrahlung enhancement must exist (in however small amount) if gluon radiative Eloss (GLV, BDPMS…) is present • can discrepancy be accounted for? Another constraint on radiative picture? • g-jet conversion seems reasonable given a QGP, where does it go wrong? (modified aS…) • Interpretation of the partonic medium? • Is there suppression in high pt gdirect? Still need more precision at high pT Justin Frantz - ISMD ‘07

  44. m Arm h = 1.7-2.4 PHENIX Central Arm |h| < 0.35 PHENIX @ RHIC Forward/Bkwd Muon Arms Central Arm Central Arm Justin Frantz - ISMD ‘07

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