[[TOC]]

= Quick Tour =

== Installing Delphes from Source ==

To successfully build Delphes the following prerequisite packages should be installed:
 - [http://root.cern.ch/drupal/content/downloading-root ROOT Data Analysis Framework]
 - [http://www.tcl.tk Tcl scripting language]

Then configure your environment for ROOT and GCC. If you are on lxplus, you can do it this way:

{{{#!sh
source /cvmfs/sft.cern.ch/lcg/views/LCG_105/x86_64-el9-gcc12-opt/setup.sh
}}}

Finally download and build Delphes:
{{{#!sh
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
{{{#!sh
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:
{{{#!sh
./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:
{{{#!sh
./DelphesHepMC3 cards/delphes_card_CMS.tcl output.root input.hepmc
}}}

Running Delphes with STDHEP (XDR) input files:
{{{#!sh
./DelphesSTDHEP cards/delphes_card_CMS.tcl delphes_output.root input.hep
}}}

Running Delphes with LHEF input files:
{{{#!sh
./DelphesLHEF cards/delphes_card_CMS.tcl delphes_output.root input.lhef
}}}

Running Delphes with files accessible via HTTP:
{{{#!sh
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:
{{{#!sh
root
gSystem->Load("libDelphes");
}}}

Open ROOT tree file and do some basic analysis using Draw or TBrowser:
{{{#!C++
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 [wiki:WorkBook/RootTreeDescription]


=== Macro-based analysis ===

The [source:examples] directory contains a basic ROOT analysis macro called [source:examples/Example1.C Example1.C].
This ROOT analysis macro consists of histogram booking, event loop (histogram filling),
histogram display.

Here are commands to run this macro:
{{{#!sh
root
gSystem->Load("libDelphes");
.X examples/Example1.C("delphes_output.root");
}}}

And here is the full source code of this macro:
{{{#!C++
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 [source:examples] directory contains a ROOT macro called [source:examples/Example2.C 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:
{{{#!sh
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 [wiki:WorkBook/DelphesAnalysis dedicated page].