[640d6d3] | 1 | Quick start with Delphes
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| 2 | ========================
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[fe6bd24] | 3 |
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[640d6d3] | 4 | Commands to get the code:
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| 5 | ```
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| 6 | wget http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.1.2.tar.gz
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| 7 |
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| 8 | tar -zxf Delphes-3.1.2.tar.gz
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| 9 | ```
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| 10 | Commands to compile the code:
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| 11 | ```
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| 12 | cd Delphes-3.1.2
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| 13 |
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| 14 | make
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| 15 | ```
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| 16 | Finally, we can run Delphes:
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| 17 | ```
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| 18 | ./DelphesHepMC
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| 19 | ```
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| 20 | Command line parameters:
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| 21 | ```
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| 22 | ./DelphesHepMC config_file output_file [input_file(s)]
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| 23 | config_file - configuration file in Tcl format
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| 24 | output_file - output file in ROOT format,
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| 25 | input_file(s) - input file(s) in HepMC format,
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| 26 | with no input_file, or when input_file is -, read standard input.
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| 27 | ```
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| 28 | Let's simulate some Z->ee events:
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| 29 | ```
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| 30 | wget http://cp3.irmp.ucl.ac.be/downloads/z_ee.hep.gz
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| 31 | gunzip z_ee.hep.gz
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| 32 | ./DelphesSTDHEP examples/delphes_card_CMS.tcl delphes_output.root z_ee.hep
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| 33 | ```
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| 34 | or
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| 35 | ```
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| 36 | curl -s http://cp3.irmp.ucl.ac.be/downloads/z_ee.hep.gz | gunzip | ./DelphesSTDHEP examples/delphes_card_CMS.tcl delphes_output.root
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| 37 | ```
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| 38 | For more detailed documentation, please visit
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| 39 |
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| 40 | https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook
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| 41 |
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| 42 |
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| 43 | Simple analysis using TTree::Draw
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| 44 | =================================
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| 45 |
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| 46 | Now we can start ROOT and look at the data stored in the output ROOT file.
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| 47 |
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| 48 | Start ROOT and load Delphes shared library:
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| 49 | ```
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| 50 | root -l
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| 51 | gSystem->Load("libDelphes");
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| 52 | ```
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| 53 | Open ROOT file and do some basic analysis using Draw or TBrowser:
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| 54 | ```
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| 55 | TFile::Open("delphes_output.root");
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| 56 | Delphes->Draw("Electron.PT");
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| 57 | TBrowser browser;
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| 58 | ```
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| 59 | Note 1: Delphes - tree name, it can be learned e.g. from TBrowser
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| 60 |
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| 61 | Note 2: Electron - branch name; PT - variable (leaf) of this branch
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| 62 |
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| 63 | Complete description of all branches can be found in
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| 64 |
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| 65 | doc/RootTreeDescription.html
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| 66 |
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| 67 | This information is also available at
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| 68 |
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| 69 | https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/RootTreeDescription
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| 70 |
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| 71 |
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| 72 | Macro-based analysis
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| 73 | ====================
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| 74 |
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| 75 | Analysis macro consists of histogram booking, event loop (histogram filling),
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| 76 | histogram display.
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| 77 |
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| 78 | Start ROOT and load Delphes shared library:
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| 79 | ```
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| 80 | root -l
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| 81 | gSystem->Load("libDelphes");
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| 82 | ```
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| 83 | Basic analysis macro:
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| 84 | ```
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| 85 | {
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| 86 | // Create chain of root trees
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| 87 | TChain chain("Delphes");
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| 88 | chain.Add("delphes_output.root");
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| 89 |
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| 90 | // Create object of class ExRootTreeReader
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| 91 | ExRootTreeReader *treeReader = new ExRootTreeReader(&chain);
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| 92 | Long64_t numberOfEntries = treeReader->GetEntries();
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| 93 |
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| 94 | // Get pointers to branches used in this analysis
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| 95 | TClonesArray *branchElectron = treeReader->UseBranch("Electron");
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| 96 |
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| 97 | // Book histograms
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| 98 | TH1 *histElectronPT = new TH1F("electron pt", "electron P_{T}", 50, 0.0, 100.0);
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| 99 |
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| 100 | // Loop over all events
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| 101 | for(Int_t entry = 0; entry < numberOfEntries; ++entry)
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| 102 | {
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| 103 |
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| 104 | // Load selected branches with data from specified event
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| 105 | treeReader->ReadEntry(entry);
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| 106 |
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| 107 | // If event contains at least 1 electron
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| 108 | if(branchElectron->GetEntries() > 0)
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| 109 | {
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| 110 | // Take first electron
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| 111 | Electron *electron = (Electron*) branchElectron->At(0);
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| 112 |
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| 113 | // Plot electron transverse momentum
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| 114 | histElectronPT->Fill(electron->PT);
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| 115 |
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| 116 | // Print electron transverse momentum
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| 117 | cout << electron->PT << endl;
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| 118 | }
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| 119 |
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| 120 | }
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| 121 |
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| 122 | // Show resulting histograms
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| 123 | histElectronPT->Draw();
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| 124 | }
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| 125 | ```
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| 126 |
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| 127 | More advanced macro-based analysis
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| 128 | ==================================
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| 129 |
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| 130 | The 'examples' directory contains ROOT macros Example1.C, Example2.C and Example3.C.
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| 131 |
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| 132 | Here are the commands to run these ROOT macros:
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| 133 | ```
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| 134 | root -l
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| 135 | .X examples/Example1.C("delphes_output.root");
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| 136 | ```
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| 137 | or
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| 138 | ```
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| 139 | root -l examples/Example1.C\(\"delphes_output.root\"\)
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| 140 | ```
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