Tutorial: Searching for top resonances using Jet Substructure

Introduction

This tutorial is based on the analysis described here (https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsEXO11006Winter2012). We will cover the jet substructure tools used to tag top and W jets.

This tutorial was designed for the CMS 2013 DAS at the LPC

Getting started

Step 1: Log in to the Fermilab LPC cluster

kinit username@FNAL.GOV
ssh -XY username@cmslpc-sl5.fnal.gov

Step 2: Checkout CMS software and set up your environment

source /uscmst1/prod/sw/cms/cshrc prod
scramv1 project -n CMSSW_5_3_3_Tutorial CMSSW CMSSW_5_3_3
cd  CMSSW_5_3_3_Tutorial/src/
cmsenv

Step 3: Check out additional code needed for this analysis

# set up CVS environment
cmscvsroot CMSSW
# check out code
addpkg PhysicsTools/PatAlgos          V08-09-14-00   
addpkg PhysicsTools/PatUtils         V03-09-22      
addpkg RecoJets/JetAlgorithms         V04-05-00      
addpkg RecoJets/JetProducers         V05-11-01      
addpkg TopQuarkAnalysis/TopPairBSM         tlbsm_53x_v2_003
addpkg UserCode/srappocc/src/Analysis/BoostedTopAnalysis         V03-02-02    
addpkg UserCode/srappocc/src/Analysis/EDSHyFT         V10-00-07   
addpkg UserCode/srappocc/src/Analysis/JetAnalysis         V02-02-00  
addpkg UserCode/srappocc/src/Analysis/SHyFT         V08-00-00  

Optional, you may need to do the following

kserver_init 
setenv CVSROOT ":gserver:isscvs.cern.ch/local/reps/CMSSW"
# login to CVS server. Password is "98passwd"
cvs login

Step 4: Run the code

cd Analysis/BoostedTopAnalysis/test/
cmsRun topresonancetutorial_cfg.py

Step 5: Examine the output root file

root histos.root
TBrowser k

Details

Lets look into the details of the code.

The constructor inculudes the initialization of some histograms using TFileService. Using this utility requires some include files and changes to the buildfile. See SWGuideTFileService.

TopResonanceTutorial::TopResonanceTutorial(const edm::ParameterSet& iConfig)
{
  edm::Service fs;

  // pretagged CATop histograms
  CATop_mass          = fs->make("CATop_mass",            "CATop_mass",         100,  0,  400 );
  CATop_minmass       = fs->make("CATop_minmass",         "CATop_minmass",      100,  0,  200 );
  CATop_nsubjets      = fs->make("CATop_nsubjets",        "CATop_nsubjets",     5,    0,  5 );
  CATop_pt            = fs->make("CATop_pt",              "CATop_pt",           100,  0,  4000 );
  CATop_eta           = fs->make("CATop_eta",             "CATop_eta",          100,  -3, 3 );  
  CATop_rapidity      = fs->make("CATop_rapidity",        "CATop_rapidity",     100,  -3, 3 );  
  CATop_dijet_mass    = fs->make("CATop_dijet_mass",      "CATop_dijet_mass",   100,  0,  4000 ); 

  // Type11 histograms
  Type11_mass       = fs->make("Type11_mass",   "measured t#bar{t} Inv Mass Type11",   500,  0,  5000 );

  // pretagged pruned jet histograms
  PrunedJet_mass        = fs->make("PrunedJet_mass",      "PrunedJet_mass",       100,  0,  400 );
  PrunedJet_pt          = fs->make("PrunedJet_pt",        "PrunedJet_pt",         100,  0,  4000 );
  PrunedJet_eta         = fs->make("PrunedJet_eta",       "PrunedJet_eta",        100,  -3, 3 );  
  PrunedJet_rapidity    = fs->make("PrunedJet_rapidity",  "PrunedJet_rapidity",   100,  -3, 3 );  
  PrunedJet_dijet_mass  = fs->make("PrunedJet_dijet_mass","PrunedJet_dijet_mass", 100,  0,  4000 ); 
  PrunedJet_mu          = fs->make("PrunedJet_mu",        "PrunedJet_mu",         100,  0,  1 );  
  PrunedJet_y           = fs->make("PrunedJet_y",         "PrunedJet_y",          100,  0,  1 );  
  PrunedJet_dR          = fs->make("PrunedJet_dR",        "PrunedJet_dR",         100,  0,  1 );  

  // Type12 histograms  
  Type12_mass       = fs->make("Type12_mass",   "measured t#bar{t} Inv Mass Type12",   500,  0,  5000 );
}

The code that is run for each event is included in void TopResonanceTutorial::analyze. A loop over the collection of jets on which the top tagging algorihm was run

 edm::Handle > h_topTag;
 iEvent.getByLabel( "goodPatJetsCATopTagPF", h_topTag );

  // Example - loop over all jets in collection

  for ( std::vector::const_iterator jetBegin = h_topTag->begin(),
      jetEnd = h_topTag->end(), ijet = jetBegin; ijet != jetEnd; ++ijet ) {
 }

References

  • CMS Papers
    • Z' → ttbar All-Hadronic Search - Public Twiki - Cadi
    • Jet substructure algorithm commisioning JME-10-013 AN2010_330_v3
    • Jet substructure algorithm optimization AN2010_080_v1
  • BOOST Conference Proceedings
    • 2010
    • 2011

-- JamesDolen - 02-Jan-2013

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Topic revision: r1 - 2013-01-02 - JamesDolen
 
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