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High p T Hadron Correlation

High p T Hadron Correlation. and No Correlation. Rudolph C. Hwa University of Oregon. Hard Probes 2006 Asilomar, CA, June 10, 2006. B. Unconventional scenario. High p T hadrons  high p T jet  correlation. A. Conventional scenario. Hard scattering  high p T jet

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High p T Hadron Correlation

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  1. High pT Hadron Correlation and No Correlation Rudolph C. Hwa University of Oregon Hard Probes 2006 Asilomar, CA, June 10, 2006

  2. B. Unconventional scenario High pT hadrons  high pT jet  correlation A. Conventional scenario Hard scattering  high pT jet  hadron correlation (usual conductor has resistance) (superconductor has no resistance)

  3. B. No Jet Correlation  and  production up to pT ~ 6 GeV/c Forward production at any pT Large pT at LHC A. Jet Correlation pT1-pT2 1-2 1-2 near side 1 away side auto-correl

  4. STAR same side

  5. In the recombination model k q1 q2 q3 q4 Associated particle pT distribution p1 -- trigger p2 -- associated

  6. STAR Associated particle distribution in the recombination model -- for  only Hwa & Tan, PRC 72, 057902 (2005)

  7. Jet tomography CGC forward production All use fragmentation for hadronization -- but not reliable at intermediate pT Remember p/ ratio in white paper All in recombination/ coalescence model TTT TT T S If proton production cannot be described by fragmentation at intermediate pT, how much trust can be placed on pion production by fragmentation? S S -- fragmentation Medium modified dihadron fragmentation function -- more relevant at higher pT. Majumder, Wang, Wang nucl-th/0412061

  8. A. Jet Correlation pT1-pT2 1-2 1-2 near side 1 away side 2 auto-correl

  9. medium effect on away-side jet Jet quenching enhancement suppression Away side

  10. Dijet fragmentation STAR, nucl-ex/0604018 enhancement suppression

  11.  production in AuAu central collision at 200 GeV recombination fragmentation Hwa & CB Yang, PRC70, 024905 (2004)

  12. STAR dijet 0.2 0.1 12 8 pT(assoc) 4 0 4 8 12 16 pT(trig)

  13. is measurable without direct knowledge of the parton energy. X.-N. Wang, Phys. Lett. B 595, 165 (2004) J. Adams et al., nucl-ex/0604018 Trigger-normalized fragmentation function Trigger-normalized momentum fraction

  14. STAR, nucl-ex/0604018

  15. STAR dijet zT=0.8-0.9 Bielcikova PANIC 05 zT=0.5-0.6 12 8 pT(assoc) 4 0 4 8 12 16 pT(trig)

  16. STAR claims universal behavior in D(zT) fragmentation violation of universal behavior due to medium effect ---- thermal-shower recombination Suggestion: look for p/ ratio in this region. Large if dominated by recombination.

  17. A. Jet Correlation pT1-pT2 1-2 1-2 near side 1 away side 2 3 auto-correl

  18. peaks Correlation on the near side  and  distributions STAR, PRL 95, 152301 (2005)

  19. energy loss converts to soft particles hard parton hard parton shower parton, leads to the trigger particle trigger hadron pedestal T=15 MeV  At higher trigger momentum, the hard parton originate closer to the surface, so less energy is lost. Hence no pedestal. Those soft particles form the pedestal. Chiu & Hwa, PRC 72, 034903 (2005) At low trigger momentum, hard partons can originate farther in.

  20. A. Jet Correlation pT1-pT2 1-2 1-2 near side 1 away side 2 3 4 auto-correl

  21. Away-side distribution Casalderrey-Solana, Shuryak, Teaney Mach cone Dremin Cherenkov gluons Ruppert, Muller color wake Koch, Majumder, WangCherenkov radiation Vitevjet quenching+fragm . . Chiu, Hwaparton multiple scattering

  22. high pT parton Parton multiple-scattering model Sample trajectories for 2.5<p(trig)<4, 1<p(assoc)<2.5 absorbed (thermalized) tracks exit tracks

  23. PHENIX 2.5<p(trig)<4 parton p=4.5 energy loss thermalized -  A new measure proposed that suppresses statistical background event-by-event Chiu & Hwa, nucl-th/0605054 Away-side  distribution Event averaged, background subtracted. Cannot distinguish between 1-jet and 2-jet contributions (e.g., Mach cone) Chiu’s talk in parallel session on Monday

  24. A. Jet Correlation pT1-pT2 1-2 1-2 near side 1 away side 2 3 4 5 auto-correl

  25. Consider an example in time series analysis Trainor (STAR) Jamaica workshop (2004) Autocorrelation

  26. Define Autocorrelation Fix and , and integrate over all other variables in The only non-trivial contribution to near , would come from jets Correlation function Treat 1,2 on equal footing --- no trigger No ambiguous subtraction procedure; only do as defined.

  27. x x k 1  p1 2 p2 q1  - q2 1 2 thermal partons y y jet axis hard parton momentum k z z pion momenta (observable) two shower partons with angular difference  (a much larger set) Radiated gluon momentum q 

  28. dominated by soft partons TS recombination in a jet with pT>3 GeV/c Chiu & Hwa, PRC 73, 014903 (2006) STAR data on Autocorrelation for central Au+Au at 130 GeV for ||1.3, 0.15<pT<2 GeV/c NO trigger, no subtraction nucl-ex/0605021

  29. B. No Jet Correlation  and  production up to pT ~ 6 GeV/c Forward production at any pT Large pT at LHC A. Jet Correlation pT1-pT2 1-2 1-2 near side 1 away side 2 3 4 5 auto-correl

  30. pT distribution of  by recombination For   and  production at intermediate pT strange-quark shower is very suppressed.

  31. Hwa & CB Yang, nucl-th/0602024 recombination hard parton scattering recombination s s s s s s fragmentation There are other particles associated with and If they are produced by hard scattering followed by fragmentation, one expects jets of particles.

  32. Predict: no associated particles giving riseto peaks in , near-side or away-side. We claim that no shower partons are involved in  production, so no jets are involved. Select events with  or  in the 3<pT<6 region, and treat them as trigger particles.

  33. p+p Jet-like structures Signal (1/Ntrig) dN/d(Df) Au+Au top 5%  trigger (pT>3 GeV/c) in Au+Au ? background Df charged hadrons

  34. B. No Jet Correlation  and  production up to pT ~ 6 GeV/c Forward production at any pT Large pT at LHC A. Jet Correlation pT1-pT2 1-2 1-2 near side 1 away side 2 3 4 5 auto-correl

  35. PHOBOS, nucl-ex/0509034 Back et al, PRL 91, 052303 (2003) Forward production of hadrons Without knowing pT, it is not possible to determine xF

  36. In pB collision the partons that recombine must satisfy p B A B But in AB collision the partons can come from different nucleons Theoretically, can hadrons be produced at xF > 1? (TFR) It seems to violate momentum conservation, pL > √s/2. In the recombination model the produced p and  can have smooth distributions across the xF = 1 boundary.

  37. proton-to-pion ratio is very large. proton • : momentum degradation factor pion Hwa & Yang, PRC 73,044913 (2006)

  38. BRAHMS, nucl-ex/0602018

  39. xF = 0.9 xF = 0.8 xF = 1.0 TFR TS TTT TT

  40.  no shower partons involved  no jets involved  no jet structure  no associated particles Hwa & Yang, nucl-th/0605037 Thermal distribution fits well

  41. B. No Jet Correlation  and  production up to pT ~ 6 GeV/c Forward production at any pT Large pT at LHC A. Jet Correlation pT1-pT2 1-2 1-2 near side 1 away side 2 3 4 5 auto-correl

  42. 2 hard partons p  1 shower parton from each  and p production at high pT at LHC New feature at LHC: density of hard partons is high. High pT jets may be so dense that neighboring jet cones may overlap. If so, then the shower partons in two nearby jets may recombine.

  43. But they are part of the background of an ocean of hadrons from other jets. GeV/c That is very different from a super-high pT jet. A jet at 30-40 GeV/c would have lots of observable associated particles. The particle detected has some associated partners. There should be no observable jet structure distinguishable from the background.

  44. single jet Proton-to-pion ratio at LHC  -- probability of overlap of 2 jet cones Hwa & Yang nucl-th/0603053

  45. We predict for 10<pT<20 Gev/c at LHC • Large p/ ratio • NO associated particles above the background

  46. B. No Jet Correlation When recombination dominates over fragmentation, B/M ratio can be very large, and there would be no jets, no jet structure and no correlation above background.  and  production up to pT ~ 6 GeV/c Forward production at any pT Large pT at LHC ? ? ? A. Jet Correlation There’s jet quenching, but not necessarily fragmentation pT1-pT2 1-2 1-2 near side Jet fragmentation at high and away side Recombination at auto-correl No trigger bias, need more data at high pT Summary

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