== 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]

Commands to download Delphes' source and build Delphes: 

{{{
setup ROOT environment variables

wget http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.0.5.tar.gz
tar -zxf Delphes-3.0.5.tar.gz

cd Delphes-3.0.5
make -j 4
}}}

== Running Delphes ==

When running Delphes without parameters or when supplying an invalid command line, the following message will be shown:
{{{
./DelphesHepMC
 Usage: DelphesHepMC 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:
{{{
./DelphesHepMC examples/delphes_card_CMS.tcl output.root input.hepmc
}}}

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

Running Delphes with LHEF input files:
{{{
./DelphesLHEF examples/delphes_card_CMS.tcl delphes_output.root input.lhef
}}}

Running Delphes with files stored in CASTOR:
{{{
rfcat /castor/cern.ch/user/d/demine/test.hepmc.gz | gunzip | ./DelphesHepMC examples/delphes_card_CMS.tcl delphes_output.root
}}}

Running Delphes with files accessible via HTTP:
{{{
curl http://cp3.irmp.ucl.ac.be/~demin/test.hepmc.gz | gunzip | ./DelphesHepMC examples/delphes_card_CMS.tcl delphes_output.root
}}}

== Analyzing Delphes' Output ==

Delphes' output can be analyzed with the ROOT data analysis framework.

=== 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::Open("delphes_output.root");
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 '''{{{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\(\"delphes_output.root\"\)
}}}