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Student Project BND - Spa September 2019

Pre-requisites

To successfully run this tutorial the following prerequisite packages should be installed:

  • gfortran/gcc/tcl:

For linux users gcc/tcl should be already installed. For Mac users you should install XCode.

  • ROOT:

can be downloaded from https://root.cern.ch/downloading-root Go on latest release, and download a version under "Binary distributions".

  • MadGraph5

a version of MG5 can be downloaded here: https://launchpad.net/mg5amcnlo/2.0/2.5.x/+download/MG5_aMC_v2.5.5.tar.gz

  • Delphes

start from here: https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/QuickTour

  • Pythia8:

following instructions from here (or using the Pythia8 installation in MadGraph):

https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/Pythia8

0) Download data sample

From the Delphes main directory, download the pseudo-data file data.root :

wget -O data.root https://cernbox.cern.ch/index.php/s/MIjpBmZmXjHmNm2/download

1) Access information in the ROOT file

Open the ROOT file (ignore the various warnings) and visualize its content via the TBrowser.

root -l data.root
TBrowser t;

Open the Delphes Tree and then Event branch (by double-clicking). How many events are in this dataset? Likewise explore the Tree content by looking at other branches.

Non trivial information can also be plotted from the command line.

TFile *f = TFile::Open("data.root");
TBrowser browser;
f->Get("Delphes")->Draw("Muon.PT");

Some information is not directly accessible from the browser interface but can nevertheless be access via command line. Every Delphes object has a 4-vector (called P4()) member of type TLorentzVector (see here for documentation: https://root.cern.ch/doc/master/classTLorentzVector.html)

So for example to plot the magnitude of the 3-momenta of the jets, or the jet invariant mass:

f->Get("Delphes")->Draw("Electron.P4().P()");
f->Get("Delphes")->Draw("Jet.P4().M()");

In order to perform an event-loop with a more sophisticated event selection you will have to write a small python macro. This macro takes as input the data.root and produce an output file that contains a couple of histograms. Download the file called example.py, and run it via the command python example.py data.root hist_data.root. This will create a file called hist_data.root that can be browsed as done earlier with data.root.

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