Example 1: Quick start with Delphes

===================================



1. Connect to ipnorsay.in2p3.fr:



  ssh -Y username@ipnorsay.in2p3.fr



2. Setup ROOT environment variables:



  use root

  

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 Z -> e-e+ events:



  ./DelphesSTDHEP examples/delphes_card_CMS.tcl step_1.root /projet/pth/delphes/Samples/z_ee.hep



or



  curl -s http://cp3.irmp.ucl.ac.be/downloads/z_ee.hep.gz | gunzip | ./DelphesSTDHEP examples/delphes_card_CMS.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("Electron.PT", "Electron.PT > 20");

  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 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 Z boson invariant mass:



  cp /projet/pth/delphes/Tutorial/InvariantMass.C .

  root -l -b -q InvariantMass.C'("step_1.root", "step_1_plots.root")'



The step_1_plots.root file contains 1 histogram of the e-e+ invariant mass.



  root step_1_plots.root

  TBrowser browser;





Example 4: Modifying configuration file

=======================================



1. Change the electron energy smearing in the configuration file:



  edit examples/delphes_card_CMS.tcl



replace resolution formula for electrons with:



  # resolution formula for electrons

  set ResolutionFormula {

                      (abs(eta) <= 3.0) * sqrt(energy^2*0.007^2 + energy*0.07^2 + 0.35^2) +

    (abs(eta) > 3.0 && abs(eta) <= 5.0) * sqrt(energy^2*0.107^2 + energy*2.08^2)

  }



2. rerun Delphes:



  ./DelphesSTDHEP examples/delphes_card_CMS.tcl step_2.root /projet/pth/delphes/Samples/z_ee.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("mee"))->SetLineColor(kBlue);

  ((TH1F *)_file1->Get("mee"))->SetLineColor(kRed);

  

  _file0->Get("mee")->Draw();

  _file1->Get("mee")->Draw("SAME");





  In step_1 electron energy resolution is given by tracker+ECAL, in step_2 only ECAL.