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High pT Hadron /Jet Suppression

High pT Hadron /Jet Suppression. Hisayuki Torii, Hiroshima Univ. Workshop at Wuhan 02/12/2008. p T assoc > 2 GeV. STAR, Phys Rev Lett 91, 072304. High p T  ’s produced at expected rate No large initial state effects. First Impact on “Jet Quenching” at RHIC.

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High pT Hadron /Jet Suppression

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  1. High pTHadron/Jet Suppression Hisayuki Torii, Hiroshima Univ. Workshop at Wuhan02/12/2008

  2. pTassoc > 2 GeV STAR, Phys Rev Lett 91, 072304 • High pT’s produced at expected rate • No large initial state effects First Impact on “Jet Quenching” at RHIC • Yield of high pT0’s suppressed • Parton energy loss reflected in softer fragmentation products • Suppression of back-to-back high pT hadrons • Recoil parton is quenched

  3. Single Hadron Measurement Di-Hadron Measurement (Correlation) Systematic Study with High-pT Hadrons STAR PRL97(2006)162301 PHENIX PRC78(2008)014901

  4. SKIN Effect in Hadron Measurements H.Z.Zhang et al. PRL98(2007)212301 + slides at ATHIC08

  5. Systematic study of single-hadron and di-hadron is very critical to understand several effects. • Flavor Dependence : g – uds – c – b • Recombination model at Middle pT •  Various identified hadrons (or electrons) • Skin Effects • Single- or Di- or Gamma-hadron • Reaction Plane Dependence • Nucleus Size Dependence (PbPbvs smaller nucleus collisions) • I will show a quick review of hadron measurement at ALICE-PHOS in following several slides. High-pTHadron as Quenching Study

  6. 0yield estimates at first (next) LHC run (p+p) Status of Analysis with ALICE-PHOS (1)

  7. Status of Analysis with ALICE-PHOS (2) AliAnalysisTaskSE AliAnalisisTaskParticleCorrelation Data Output:AliAODParticleCorrelation and/or AliAODCaloClusters and/or Histograms Data AliAODCaloTrackReader ESD, AOD, MC AliAnaPartCorrMaker aodEMCal, aodPHOS, aodCTS aodEMCal, aodPHOS, aodCTS aodParticleCorr AliAnaPi0 derives from AliAnaPartCorrBaseClass

  8. Geometrical Acceptance • Determined by 0 decay kinematics • Flat acceptance at pT>10GeV/c • Reconstruction Efficiency • Because of finite energy and position resolution of PHOS and steep slope of 0pT slope, so called “Smearing Effect” appear. • This causes the efficiency is not equal to 100%. • The effect depends on the PHOS calibration • Detail analysis of PHOS calibration is on going. Status of Analysis with ALICE-PHOS (3)

  9. Conversion Probability • Photons from 0 can be lost due to interactions between other detectors  Conversion Loss • 20% loss is expected • Off-Vertex Contribution • 0 can be produced at the other detectors • Ex. +0 + X 0 + X’ • <1% Status of Analysis with ALICE-PHOS (4) Further details including eta/omega measurement with PHOS  See Renzhuo’s Talk

  10. Hadronvs Jet Measurements Leading Hadron • BAD: Surface emission “trigger bias” leading to • Small sensitivity of RAA to variations of transport parameter qhat. • Yields only lower limit on color charge density. • For increasing in medium path length L leading particle is less and less correlated with jet 4-momentum. • Good • No experimental bias unlike jet identification • Bad: Bias in jet finding algorithm • Ideally, the analysis of reconstructed jets will allow us to measure the original parton 4-momentum and the jet structure (longitudinal and transverse). • Measuring the recoil direct photon from +jet processes would provide direct measurement of the parton energy (@LO) • “Golden” measurement, but difficult due to low rate and huge backgrounds Reconstructed Jet

  11. Naively, gluon jet is quenched more than quark jet • Strong Interaction Color Factor C(A) : C(F) = 3 : 4/3 • Comparison between gluon and quark  Extreame test of quenching effect Gluon vs Quark Jets Photon-Jets Single/Di-Hadrons/Jets PYTHIA Pi0 at 14TeV PYTHIA 5.5TeV PYTHIA 5.5TeV Quark Dominant Gluon Dominant GOLDEN measurement

  12. An Idea of How to See Gluon/Quark Photon-Jets Single/Di-Jets PYTHIA 5.5TeV PYTHIA 5.5TeV Quark Dominant Gluon Dominant Statistics: Good (<150-200GeV/c : EMCal) Statistics: Bad (<40GeV/c with EMCAL) Upgrade of EMCalwith Trigger is critial Caveat: Difficult due to huge background. Hard to obtain a reference measurement at p+p

  13. An Idea of How to See Gluon/Quark Photon-Jets Single/Di-Jets Tri-Jets Naively, the gluon/quark ratio is much more than that in di-jets because of additional gluon radiation PYTHIA 5.5TeV PYTHIA 5.5TeV Quark Dominant Gluon Dominant More Gluon? Statistics: Good (up to 150-200GeV/c) Statistics: Bad (up to 40GeV/c) Statistics: ??? EMCal with Trigger What do we need? Upgrade of ALICE? Caveat: Difficult due to huge background. Hard to obtain a reference measurement at p+p

  14. GR@PPA • “GRace At Proton-Proton/Antiproton collisions” • One of existing NLO-pQCD event generator in the world. • Developed by KEK theory group. • Fortran • Fragmentation by string model in PYTHIA • Familiar interface for PYTHIA fortrun users. • Many channels including 2,3,4jets. • Analysis • Instead of employing a jet finding algorithm (kT or cone), following cuts were applied on the 2 or 3 parton kinematics. • pT of each parton > 10GeV/c • Rapidity of all parton < +-1.4 • Distance between two partons > 0.4 in eta/phi space. • This is first view of tri-jet effect. An NLO-pQCD Event Generator

  15. 3-jets contribution is suppressed strongly at pt<50GeV/c because of requirement on jets • Gluon/Quark jets ratio decrease from 12% to 9% at 20GeV/c • A little smaller than naïve expectation • More detail analysis is on going. • Question : How the surface effect is different between tri and di? Ratio of Tri-Jets and Di-Jets by GR@PPA

  16. Just an Idea about How to Measure? From ALICE-EMCalProporsal • Inclusive/Di-jet estimation exist with EMCal • Inclusive Jets measurement at EMCal by two different trigger • Triggered by another jets (detected by TPC) at 180deg direction in azimuthal plane. • Triggered by two jets (detected by TPC) not at 180deg direction in azimuthal plane • Both statistics must be enough up to 160GeV/c • Jet shape analysis • Hadron multiplicity inside the jets • Question: How to define the scale of jet? 10k/year

  17. Systematic study of single/di-hadron measurements • Critical to separate various effect • High pt hadron measurement with PHOS is on going • Jet measurement • Sensitive to modification of fragmentation function • Gluon/Quark separation is critical test on quenching effect, so gluon density in QGP • Tri-Jet for gluon jet enhancement • An idea of enhancing gluon jets more than single/di-jet measurement  Tri-Jet • First estimate of yield: Comparable with Di-jet. • Upgrade at ALICE? Summary

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