Delphes Tutorial - DESY March 2020

Pre-requisites

To successfully run this tutorial the Delphes virtual machine should be installed, see here for more information:

​https://twiki.cern.ch/twiki/bin/view/VBSCan/PREFIT20

If you have successfully produced Pythia8 event files in the MadGraph and Parton Shower lecture (Admir Greljo, Ilaria Brivio), copy (or move) the pp->ll (SM and BSM) into the Delphes directory Delphes-3.4.2

FIXME: find out how these files where named during tutorial

If not you can download the files from here (but it might take a while):

cd Delphes-3.4.2
curl -o pp_ll_sm.hepmc  https://cernbox.cern.ch/index.php/s/4rnlQ0bybBYvLTS/download
curl -o pp_ll_bsm.hepmc  https://cernbox.cern.ch/index.php/s/Y71ZOw8ZiWWE0p2/download

The solution for these (simple) exercises can be found in the attached file tutorial_solution.txt, located at the bottom of this page. Consult it if you are stuck but before try to solve the question by yourself.

I) Produce Delphes root files

In this section you will run Delphes Fast Detector simulation using the default CMS card. Delphes will produce a ROOT file starting from the hepmc format produced by MG5+Pythia8.

Produce two delphes output files, one for the sample SM and one for the BSM sample (pp_ll_sm.root and pp_ll_bsm.root), using the DelphesHepMC executable and the CMS configuration card cards/delphes_card_CMS.tcl.

Hint: The command to produce a Delphes output

./DelphesHepMC cards/delphes_card.tcl output.root input.hepmc

II) Simple Interactive Tree analysis

1) Open the (pp_ll_sm.root Delphes ROOT tree and explore the branches, plot the electrons transverse momentum. 2) Draw the muon and electron multiplicity via the ROOT command line.Do you understand these distributions? 3) Compare the leading muon transverse momentum and pseudo-rapidity in the SM and the BSM sample.

III) Write a simple analysis macro

1) Write a python analysis macro examples/InvariantMass.py that selects two electrons or muons and produces the histograms of the invariant mass. To see an example check out examples/Example1.py.

2) Run the analysis macro on the pp_ll_sm.root and pp_ll_bsm.root samples.

3) Plot the di-electron and di-muon invariant on the same plot for both the SM sample. Which final state provides the best resolution? Why?

4) Plot the di-electron and di-muon invariant on the same plot for both the BSM sample. Which final state provides the best resolution? Why?

IV) Modify the Delphes detector card

You have now produced a Delphes simulated event with the hypothetical CEPC default detector configuration.

1) Can you think of 2 detector parameters that determine and drive the sensitivity of the Higgs recoil measurement in this particular final state?

2) Identify where they are configured in the delphes detector card.

3) Create two new detector configurations by degrading these two parameters by a sizable factor.

4) Reproduce a Delphes sample with these new configurations and observe the impact on the recoil mass distribution.