Example 1: Quick start with Delphes
===================================

1. Connect to LXPLUS:

  ssh -Y username@lxplus.cern.ch

2. Setup GCC and ROOT:

  for bash:
  
  source /afs/cern.ch/sw/lcg/external/gcc/4.7/x86_64-slc6/setup.sh
  source /afs/cern.ch/sw/lcg/app/releases/ROOT/5.34.18/x86_64-slc6-gcc47-opt/root/bin/thisroot.sh

  for [t]csh:
  
  source /afs/cern.ch/sw/lcg/external/gcc/4.7/x86_64-slc6/setup.csh
  source /afs/cern.ch/sw/lcg/app/releases/ROOT/5.34.18/x86_64-slc6-gcc47-opt/root/bin/thisroot.csh
  
3. Commands to get the code:

  wget http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.1.2.tar.gz

  tar -zxf Delphes-3.1.2.tar.gz

4. Commands to compile the code:

  cd Delphes-3.1.2

  make -j 4

5. Finally, we can run Delphes:

  ./DelphesSTDHEP
 
6. and simulate some ee->ZH->mumubb events:

  ./DelphesSTDHEP examples/delphes_card_FCC_basic.tcl step_1.root /afs/cern.ch/user/s/selvaggi/public/delphes_tuto/ee_zh_mmbb.hep

or

  curl -s http://cp3.irmp.ucl.ac.be/downloads/delphes_tuto/ee_zh_mmbb.hep.gz | gunzip | ./DelphesSTDHEP examples/delphes_card_FCC_basic.tcl step_1.root


Example 2: Simple analysis using TTree::Draw
============================================


Now we can start ROOT and look at the data stored on the tree

1. Start ROOT and load shared library:

  root -l
  gSystem->Load("libDelphes");

2. Open ROOT tree file and do some basic analysis using Draw or TBrowser:

  TFile::Open("step_1.root");
  Delphes->Draw("Muon.PT", "Muon.PT > 20");
  Delphes->Draw("Jet.PT", "Jet.BTag > 0");
  TBrowser browser;

Note 1: Delphes - tree name, it can be learnt e.g. from TBrowser

Note 2: Muon - branch name; PT - variable (leaf) of this branch

Complete description of all branches can be found in

  Delphes/doc/RootTreeDescription.html

This file is also available via web:

  http://cp3.irmp.ucl.ac.be/downloads/RootTreeDescription.html


Example 3: Macro-based analysis
===============================


Analysis macro consists of histogram booking, event loop (histogram filling),
histogram display

Delphes/examples contains macros Example1.C, Example2.C and Example3.C

1. Here are commands to run a macro reconstructing the Higgs invariant mass:

  cp /afs/cern.ch/user/s/selvaggi/public/delphes_tuto/InvariantMass.C .
  root -l -b -q InvariantMass.C'("step_1.root", "step_1_plots.root")'

The step_1_plots.root file contains 2 histograms of uncorrected and
corrected b-bbar invariant mass


Example 4: Modifying configuration file
=======================================

1. Change the calorimeter granularity in the configuration file:

  edit examples/delphes_card_FCC_basic.tcl

replace ECAL and HCAL phi and eta bins with:

  # 1 degree towers
  set PhiBins {}
  for {set i -180} {$i <= 180} {incr i} {
    add PhiBins [expr {$i * $pi/180.0}]
  }

  # 0.01 unit in eta up to eta = 6
  for {set i -600} {$i <= 600} {incr i} {
    set eta [expr {$i * 0.01}]
    add EtaPhiBins $eta $PhiBins
  }

2. rerun Delphes:

  ./DelphesSTDHEP examples/delphes_card_FCC_basic.tcl step_2.root /afs/cern.ch/user/s/selvaggi/public/delphes_tuto/ee_zh_mmbb.hep

3. redo the invariant mass histograms:

  root -l -b -q InvariantMass.C'("step_2.root", "step_2_plots.root")'

4. compare histograms:
  
  root -l step_1_plots.root step_2_plots.root
  
  ((TH1F *)_file0->Get("mbb_corr"))->SetLineColor(kBlue);
  ((TH1F *)_file1->Get("mbb_corr"))->SetLineColor(kRed);
  
  _file0->Get("mbb_corr")->Draw();
  _file1->Get("mbb_corr")->Draw("SAME");

5. You could also try to change the energy resolution of ECAL and/or HCAL.