EMCAL FastJet Analysis

Introduction

Using the FastJet package for jet finding using ALICE EMCAL data. Purpose is to run the package in the HLT for selecting jets meeting certain criteria.

Steps to be followed:

  • Create MC jets
  • Do the reconstruction
  • Run FastJet (mainly with anti-kt algorithm)
  • Optimize the performance
  • Implement and commission the HLT jet trigger component

Create MC jets

Using all detectors in the simulation and one ptHardBin producing 10,000 events:

    case kPythia6Jets104_125:
    {
        comment = comment.Append(":Pythia jets 105-125 GeV @ 7.00 TeV");
        AliGenPythia * gener = new AliGenPythia(-1);
        gener->SetEnergyCMS(7000.);//        Centre of mass energy
        gener->SetProcess(kPyJets);//        Process type
        gener->SetJetEtaRange(-0.5, 0.5);//  Final state kinematic cuts
        gener->SetJetPhiRange(0., 360.);
        gener->SetJetEtRange(10., 1000.);
        gener->SetGluonRadiation(1,1);
        //   Structure function
        gener->SetStrucFunc(kCTEQ4L);
        gener->SetPtHard(104., 125.);// Pt transfer of the hard scattering
        gener->SetPycellParameters(2., 274, 432, 0., 4., 5., 1.0);
        gener->SetForceDecay(kAll);//  Decay type (semielectronic, etc.)
        gener->SetProjectile("p", 1, 1) ;
        gener->SetTarget("p", 1, 1) ;
        gGener=gener;
      }

Run the reconstruction

Full reconstruction:

void rec() {
  AliReconstruction reco;

  reco.SetWriteESDfriend(kTRUE);
  reco.SetFractionFriends(1.0);
  reco.SetWriteAlignmentData();

  reco.SetDefaultStorage("local://$ALICE_ROOT/OCDB");
  reco.SetSpecificStorage("GRP/GRP/Data",
                          Form("local://%s",gSystem->pwd()));
  reco.SetRunPlaneEff(kTRUE);

  TStopwatch timer;
  timer.Start();
  reco.Run();
  timer.Stop();
  timer.Print();
}

Run FastJet

  • TPC tracks + "tracks" from EMCal
  • |η| < 0.5 in jets
  • 1.08 < φ < 2.7 (107 degrees acceptance of EMCal subtracting a "keepOut" zone of R=0.4) in jets
  • AntiKt algorithm, with R=0.4 and maximum rapidity up to which ghosts are generated 0.9
  • Following plots without background subtraction

"particle": what's coming out of MC, "detector": what's coming out of the reconstruction

1,000 events, without φ cut, without EMCal clusters

img88872c3465e8af43a2ebbe3506bed303.gif img0982212400a3cdc7a8338f805531c6a0.gif
pT of tracks at detector level pT of tracks at particle level

img249c7717577b0c5d99f0b6f1c4a1674f.gif img33b1894ef03286c3f927a885ce1ea911.gif
pT distribution of jets at detector level pT distribution of jets at particle level

imgc2ca7664e5d41f4042a2fe94fce3101c.gif img8999ee3b2a7582dd042efac4196817dc.gif
Eta distribution of jets at detector level Phi distribution of jets at detector level

img47f94b224358bdb61a1e1a27b4ede14a.gif img54540f7fa205c998a51b458e34cda374.gif
(Eta_particle - Eta_detector) distribution of jets (Phi_particle - Phi_detector) distribution of jets

img44654d7446d166fdb62d4bf3cf1a4af6.gif img219952047874c8bdaebb82b775699c2a.gif
(pT_particle - pT_detector) distribution of jets

10,000 events, with φ cut, with EMCal clusters

img71c93daf19cd934fe769c73116285fc8.gif imgfb25599e06cefcb030a27cd77e0f8cbe.gif
pT distribution of jets at detector level pT distribution of jets at particle level

img5b631ff036898bbb87b16aec866f3590.gif img843f32b9fa1b21535d4b07ac03d2d3d3.gif
Eta distribution of jets at detector level pT distribution of particle (red) and detector (black) jets

img716cbf489e443b027233feaf9145b0f7.gif imgcf73860f0897f8db4e198abd6d9655a3.gif
(Eta_particle - Eta_detector) distribution of jets (Phi_particle - Phi_detector) distribution of jets

img098358413adf278b246dad40eb14159f.gif img08bed7f9552ad4e7f0d34c1ad04a24b3.gif
(pT_particle - pT_detector) distribution of jets

10,000 events, with φ and additional cuts, with EMCal clusters

  • Additional cuts: tracks pT > 0.7 GeV and jets' pT > 50 GeV

imga01eeb3af058cdd0d9511c741019f7f5.gif img8c402c7b93c79200896b9527282f01cb.gif
pT distribution of jets at detector level pT distribution of jets at particle level

img1773d7de73c0396774a3a6714454d8ea.gif
pT distribution of jets at particle level (red) and at detector level (black)

imge0bd3ac33c865a00f0c08e8d0091e676.gif img03b3411e1f5e33e8043d61399154890c.gif
Eta distribution of jets at detector level Eta-Phi distribution of EMCal clusters

imga5ba942186a66c73dd4fdbd6d6796e63.gif img98bf68e851794bf9179f942a108ec04c.gif
(Eta_particle - Eta_detector) distribution of jets (Phi_particle - Phi_detector) distribution of jets

img46379e03967c9b785ee6128a7fca9ae5.gif imgfe094199d93a817343efc461a338585d.gif
(pT_particle - pT_detector) distribution of jets

img1bbe5cd150ec325700d9d51933cabfa9.gif imgd12959892a6847d810b59c841a5f75f5.gif
Neutral Energy Fraction distribution of jets Sum(Neutral particle pT)/(Jet pT) Fragmentation Function of jets (Particle pT)/(Jet pT)

10,000 events, with φ and additional cuts, with EMCal clusters, removed energy double counting

  • Additional cuts: tracks pT > 0.7 GeV and jets' pT > 50 GeV
  • Removed double counting of energy from charged tracks. Sum the P of all tracks matched per cluster and subtract that from the energy of the cluster; that corrected energy is used in FastJet

img853e362fa7d6575f35f71d70551faa49.gif imgc66b3c6d2ffb29e31343325795507f0f.gif
pT distribution of jets at detector level pT distribution of jets at particle level

imge6b4165540216ef9076bd282a6752e5d.gif
pT distribution of jets at particle level (red) and at detector level (black)

img4ae6cd02703c6000865b99190492923e.gif imge7b355dd5c8f2f321a8f39166b6ff360.gif
(Eta_particle - Eta_detector) distribution of jets (Phi_particle - Phi_detector) distribution of jets

img3088455ea508e5235e8701041050ece8.gif imga3f44b748245e43699ff5afd188cf2a8.gif
(pT_particle - pT_detector) distribution of jets Correlation (pT_particle - pT_detector)/(pT_particle + pT_detector)

img19755243db305daf48a3de37ca24afa1.gif img03dcca27620c3625e34966770ffeb68c.gif
Neutral Energy Fraction distribution of jets Sum(Neutral particle pT)/(Jet pT) Correlation Y projection

Implementation and commission of the HLT jet trigger component

Done HLT/trigger/AliHLTTriggerFastJet.cxx

Useful links


Major Updates: LeonidasXaplanteris - 04 August 2011

Responsible: LeonidasXaplanteris

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Topic revision: r8 - 2011-08-10 - LeonidasXaplanteris
 
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