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Table of Contents
Quick Tour
Installing Delphes from Source
To successfully build Delphes the following prerequisite packages should be installed:
Then configure your environment for ROOT and GCC. If you are on lxplus, you can do it this way:
source /cvmfs/sft.cern.ch/lcg/views/LCG_105/x86_64-el9-gcc12-opt/setup.sh
Finally download and build Delphes:
wget http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.5.0.tar.gz tar -zxf Delphes-3.5.0.tar.gz cd Delphes-3.5.0 make -j 4
Or, to install with CMake
cd Delphes-3.5.0 mkdir build cd build cmake -DCMAKE_INSTALL_PREFIX=../install .. make -j 4 install
Running Delphes
When running Delphes without parameters or when supplying an invalid command line, the following message will be shown:
./DelphesHepMC3 Usage: DelphesHepMC3 config_file output_file [input_file(s)] config_file - configuration file in Tcl format, output_file - output file in ROOT format, input_file(s) - input file(s) in HepMC format, with no input_file, or when input_file is -, read standard input.
Running Delphes with HepMC input files:
./DelphesHepMC3 cards/delphes_card_CMS.tcl output.root input.hepmc
Running Delphes with STDHEP (XDR) input files:
./DelphesSTDHEP cards/delphes_card_CMS.tcl delphes_output.root input.hep
Running Delphes with LHEF input files:
./DelphesLHEF cards/delphes_card_CMS.tcl delphes_output.root input.lhef
Running Delphes with files accessible via HTTP:
curl http://cp3.irmp.ucl.ac.be/~demin/test.hepmc3.gz | gunzip | ./DelphesHepMC3 cards/delphes_card_CMS.tcl delphes_output.root
Analyzing Delphes Output
Delphes output can be analyzed with the ROOT data analysis framework. This can be done in simple cases with TTree::Draw, or with macros for more advanced cases. Examples and mini analysis frameworks are provided in C++ (using ExRootAnalysis) and Python (using DelphesAnalysis).
Simple analysis using TTree::Draw
Start ROOT and load Delphes shared library:
root gSystem->Load("libDelphes");
Open ROOT tree file and do some basic analysis using Draw or TBrowser:
TFile *f = TFile::Open("delphes_output.root"); f->Get("Delphes")->Draw("Electron.PT"); TBrowser browser;
Note 1: Delphes - tree name, it can be learnt e.g. from TBrowser
Note 2: Electron - branch name; PT - variable (leaf) of this branch
Complete description of all branches can be found at WorkBook/RootTreeDescription
Macro-based analysis
The examples directory contains a basic ROOT analysis macro called Example1.C. This ROOT analysis macro consists of histogram booking, event loop (histogram filling), histogram display.
Here are commands to run this macro:
root gSystem->Load("libDelphes"); .X examples/Example1.C("delphes_output.root");
And here is the full source code of this macro:
void Example1(const char *inputFile) { gSystem->Load("libDelphes"); // Create chain of root trees TChain chain("Delphes"); chain.Add(inputFile); // Create object of class ExRootTreeReader ExRootTreeReader *treeReader = new ExRootTreeReader(&chain); Long64_t numberOfEntries = treeReader->GetEntries(); // Get pointers to branches used in this analysis TClonesArray *branchJet = treeReader->UseBranch("Jet"); TClonesArray *branchElectron = treeReader->UseBranch("Electron"); // Book histograms TH1 *histJetPT = new TH1F("jet_pt", "jet P_{T}", 100, 0.0, 100.0); TH1 *histMass = new TH1F("mass", "M_{inv}(e_{1}, e_{2})", 100, 40.0, 140.0); // Loop over all events for(Int_t entry = 0; entry < numberOfEntries; ++entry) { // Load selected branches with data from specified event treeReader->ReadEntry(entry); // If event contains at least 1 jet if(branchJet->GetEntries() > 0) { // Take first jet Jet *jet = (Jet*) branchJet->At(0); // Plot jet transverse momentum histJetPT->Fill(jet->PT); // Print jet transverse momentum cout << jet->PT << endl; } Electron *elec1, *elec2; // If event contains at least 2 electrons if(branchElectron->GetEntries() > 1) { // Take first two electrons elec1 = (Electron *) branchElectron->At(0); elec2 = (Electron *) branchElectron->At(1); // Plot their invariant mass histMass->Fill(((elec1->P4()) + (elec2->P4())).M()); } } // Show resulting histograms histJetPT->Draw(); histMass->Draw(); }
More advanced macro-based analysis
The examples directory contains a ROOT macro called Example2.C demonstrating how to use class ExRootTreeReader
to
access data and class ExRootResult
to manage histograms booking and output.
This macro can be run with the following command:
root -l examples/Example2.C'("delphes_output.root")'
Analysis in Python
DelphesAnalysis is an analysis framework written in Python where a clear separation is maintained between the standard code and what the user has to implement. This makes it easy to apprehend and generic, still retaining full flexibility and scalability. It is configured in a single configuration file.
More details and examples on the dedicated page.