HEP MC and Data Analysis Tutorial

Tutorial for the Particle Phisics Summer School at Udine University, July 2018 and July 2019.

Re-proposed as part of the classes "Particelle e Interazioni Fondamentali", Master Degree in Mathematics, University of Udine, April-May 2019.

References

MadGraph

• homepage: http://madgraph.hep.uiuc.edu/
• download page: https://launchpad.net/mg5amcnlo

Delphes

• homepage: https://cp3.irmp.ucl.ac.be/projects/delphes
• list of branches: https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/RootTreeDescription

ROOT

• homepage: http://root.cern.ch/drupal/
• reference guide: http://root.cern.ch/root/html/

Tutorial

1. Entering:

• We will need it to connect to the remote machine (INFN Trieste computing farm) to run the simulation and the analysis code.
  • Get the software MobaXTerm: https://download.mobatek.net/1112019010310554/MobaXterm_Portable_v11.1.zip

• Extract it and run it
  • insert the following as "Find existing session or server name...": pinamont@farmts.ts.infn.it
  • at the top select "SSH" (first option)
  • a password will be asked; insert: Lilapause13, then press ENTER
    • click on YES when asked about saving password
  • you should be redirected to this directory: tutorial_udine_2018
    • to check it type pwd and press the ENTER key
    • you should see /gpfs/atlas/pinamont/tutorial_udine_2018

• Tips on MobaXTerm usage:
  • you have a "terminal" and a "file manager" (on the left)
  • terminal commands (unix / bash commands):
    • ls list content of current directory
    • pwd show current directory full path
    • cd myDirectory enter the directory with given name
    • cd .. go back by one directory
    • source myScript.sh or ./myScript.sh exectute the script / program myScript.sh
  • file manager:
    • double-click on a directory to enter it
    • double-click on a text file to open it
    • double click on the .. to go back one directory
    • to open images, double-click should work as well; if it doesn't, need to download them: use the right-click menu
  • next time you open MobaXTerm, can restore session (i.e. don't need to copy-paste pinamont@farmts.ts.infn.it again and to type password, if saved before)

2. Setup:

• Only the first time you enter, type in your terminal (provided that you are in the /gpfs/atlas/pinamont/tutorial_udine_2018 directorry):

./setup.sh yourname

• Whenever you come back with a fresh terminal, you just need to do:

cd yourname
source setup.sh

• Go and modify the file: MG5_aMC_v2_3_3/input/mg5_configuration.txt
  • in order to have this line: text_editor = nano
  • IMPORTANT: you also need to delete the "#" at the beginning of the line!
  • Hint: use the text editor inside MobaXterm to modify the text file (from the left part of the screen), or you can use the nano text editor from the command line

• Hints on nano text editor usage:
  • only keyboard, no mouse
  • use arrows to navigate
  • Ctrl+O to save (followed by ENTER if you really want to save)
  • Ctrl+X to exit

• Now, we can enter the MG software and try it:
  • type:

cd MG5_aMC_v2_3_3
./bin/mg5_aMC

• You are now inside the MG5 shell
  • say "no" to question if asked for upgrade
• From inside MG5 type:

install pythia-pgs
install Delphes

3. Generate Signal:

• We will now generate simulated Higgs -> ZZ events

• From inside MG5 (if not yet in, type ./bin/mg5_aMC from /gpfs/atlas/pinamont/tutorial_udine_2018/yourname/MG5_aMC_v2_3_3), type:

import model heft
generate p p > h > l+ l- l+ l-
output h4lep

• Now enter the directory that got created and run the generation of the events:

cd h4lep
./bin/generate_events

• When prompted switch ON Pythia and Delphes
  • HINT: type "1" and ENTER, then "3" and ENTER, and then just ENTER
• Modify the run card to set CME = 8 TeV (energy per beam = 4 TeV)
  • HINT: type "2" and ENTER to open the text file, then modify the proper lines from 6500 to 4000 (two of them!), then save the file (Ctrl+O) and exit (Ctrl+X)
• Make sure Higgs mass is set it to 125 GeV * HINT: same as above, but type "1" (in principle you don't need to modofy anything)
• Then go back to the MG5_aMC_v2_3_3 directory:

cd ..

4. Generate Background:

• We will now generate simulated background events

• From inside MG5 (if not yet in, type ./bin/mg5_aMC from /gpfs/atlas/pinamont/tutorial_udine_2018/yourname/MG5_aMC_v2_3_3), type:

generate p p > l+ l- l+ l- /h
output zz4lep

• Now enter the directory that got created and run the generation of the events:

cd zz4lep
./bin/generate_events

• When prompted switch ON Pythia and Delphes
  • and modify the run card to set CME = 8 TeV (energy per beam = 4 TeV)
• Then go back to the MG5_aMC_v2_3_3 directory:

cd ..

5. Create Histogram for data, signal and background:

• Now we will use ROOT to process the "real data" and the simulated samples we just produced
  • ROOT "macros" are provided for you, so that you can use them without knowing how to program in C++, but it can be instructive to look inside them at some point!

• Go inside the Delphes directory (provided that you are under /gpfs/atlas/pinamont/tutorial_udine_2018/yourname/MG5_aMC_v2_3_3):

cd Delphes

• And now let's run these three command lines, that execute the ROOT macros to transform the three data-sets into histograms:

root -l -b -q '../../MyHiggs4l.C("../../data_events.root","data")'
root -l -b -q '../../MyHiggs4l.C("../h4lep/Events/run_01/tag_1_delphes_events.root","signal")'
root -l -b -q '../../MyHiggs4l.C("../zz4lep/Events/run_01/tag_1_delphes_events.root","background")'

• You can look at the results in the form of pictures showing the histograms by opening the .png files created after each step

6. Merge the histograms

• Another ROOT macro is ready for you to use, to merge the three histograms in a nice plot, showing signal + background compared to data
  • type (provided that you are under /gpfs/atlas/pinamont/tutorial_udine_2018/yourname/MG5_aMC_v2_3_3/Delphes):

root -l -b -q '../../MyHistMerger.C'

• And now you can finally see your nide plot: HiggsMass.png (under /gpfs/atlas/pinamont/tutorial_udine_2018/yourname/)

--Main.MichelePinamonti - 2019-07-23