1 / 17

High pT Hadron and Jet Suppression: Insights from RHIC and ALICE Experiments

This presentation reviews significant findings regarding high momentum (pT) hadrons and jet suppression effects from the STAR and ALICE experiments. Key results include the measurement of high pT π0 production and its suppression, with evidence of parton energy loss and softer fragmentation products. The study discusses flavor dependence, systematic studies of single and di-hadron measurements, and the calibration challenges faced by the PHOS detector. Also highlighted are the differences between quark and gluon jets, offering insights into the dynamics of parton interactions in heavy ion collisions.

lilly
Télécharger la présentation

High pT Hadron and Jet Suppression: Insights from RHIC and ALICE Experiments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related