Parallelized MadGraph Simulation¶

MadGraph is a framework that aims at providing all the elements necessary for SM and BSM phenomenology, such as the computations of cross sections, the generation of hard events and their matching with event generators, and the use of a variety of tools relevant to event manipulation and analysis. Collider processes can be simulated to LO accuracy for any user-defined Lagrangian. These user-defined models are usually generated through the FeynRules package, which you can read about and download here. For more information on MadGraph, see the launchpad site.

Preliminaries¶

In this tutorial, we’ll be using MadGraph to generate collision events for a specific process and then Pythia and Delphes to shower, hadronize, and simulate the response of an actual detector. We’ll use the titan cluster to repeat this process a number of times in order to sample the model parameter space for a BSM model. The example BSM model we’ll use consists of a single Majorana fermion and a single scalar with U(1)_EM charge +1. The Majorana nature of the fermion induces lepton number violation (LNV) in certain processes. At high energy, this LNV manifests as same-sign lepton production. It is this process which we’ll be interested in simulating and we’ll specifically be interested in simulating these processes using the estimated specs for a proposed detector at a 100 TeV future circular hadron collider. In order to simulate the response of a detector at a 100 TeV collider, we’ll use a tcl script which tells Delphes the specs of the detector it should simulate. The specific tcl script we’ll use borrows heavily from a script created by Heather Gray and Filip Moortgat for FCC detector studies.

Installations¶

Here, we’ll install MadGraph, Pythia, and Delphes. In order to set everything up, log into titan, cd into the local folder, open a text editor, paste in the following script

#!/bin/bash

echo ''
echo 'Downloading MadGraph...'
echo ''
wget -P $HOME/local https://launchpad.net/mg5amcnlo/2.0/2.4.x/+download/MG5_aMC_v2.4.3.tar.gz
cd $HOME/local
tar xzf MG5_aMC_v2.4.3.tar.gz
sed -i -e 's/# auto_update = 7/auto_update = 0/g' MG5_aMC_v2_4_3/input/mg5_configuration.txt
sed -i -e 's/# automatic_html_opening = True/automatic_html_opening = False/g' MG5_aMC_v2_4_3/input/mg5_configuration.txt
rm MG5_aMC_v2.4.3.tar.gz

echo ''
echo 'Downloading LNV model...'
echo ''
git clone https://github.com/pwinslow/Titan-Docs.git
mv Titan-Docs/LNVatLHC_UFO MG5_aMC_v2_4_3/models
rm -rf Titan-Docs

echo ''
echo 'Downloading Pythia...'
echo ''
wget -O $HOME/local/MG5_aMC_v2_4_3/pythia-pgs.tar.gz http://madgraph.phys.ucl.ac.be/Downloads/pythia-pgs_V2.4.5.tar.gz
cd $HOME/local/MG5_aMC_v2_4_3/
tar xzf pythia-pgs.tar.gz
rm pythia-pgs.tar.gzcd pythia-pgs/src
echo ''
echo 'Building Pythia. This may take a little while...'
echo ''
make all

echo ''
echo 'Downloading Delphes...'
wget -O $HOME/local/MG5_aMC_v2_4_3/Delphes.tar.gz http://cp3.irmp.ucl.ac.be/downloads/Delphes-3-current.tar.gz
cd $HOME/local/MG5_aMC_v2_4_3/
tar xzf Delphes.tar.gz
rm Delphes.tar.gz
mv Delphes-3.3.3 Delphes
cd Delphes
echo ''
echo 'Building Delphes. This may take a little while...'
echo ''
make

echo ''
echo 'Downloading 100 TeV delphes detector simulation card...'
echo ''
wget -P $HOME/local/MG5_aMC_v2_4_3/Delphes/cards https://raw.githubusercontent.com/pwinslow/Machine-Learning-Projects/master/Lepton-Number-Violation-at-100-TeV/Data_Production/PW_FCC_delphes_card.tcl
echo ''
echo 'Finished MadGraph+Pythia+Delphes setup...'

save it as MGsetup.sh, make it an executable with chmod +x MGsetup.sh, and run it with ./MGsetup.sh. This script will first download a fresh copy of MadGraph and unpack it. It then will download the FeynRules-generated BSM model we’ll work with and place it in the models folder so we can use it. After this, it will download and install both pythia and Delphes in the main MG5_aMC_v2_4_3 folder. Finally, it will download the specially designed tcl script mentioned above to simulate a detector in a 100 TeV hadron collider and place it in the delphes cards folder.

Parallelized Simulation¶

In this section, we’ll take a simple BSM process and run it on the titan cluster for a single point in the BSM parameter space. To begin, cd to the local folder, open a text editor, paste in the following script

import model LNVatLHC_UFO
generate p p > sp~ sp @1
add process p p > sp sp~ j @2
output testrun

and save it as mgscript.cmd. To run it, cd into the MG5_aMC_v2_4_3 folder and type the cmd ./bin/mg5_aMC ../mgscript.cmd. This will create MadGraph output in the testrun folder for pair production of two new charged scalars. In order to demonstrate how to run parallel simulations of this process on titan, cd back to the local folder, open a text editor, paste in the following script

#/bin/sh

MGbase=$HOME/local/MG5_aMC_v2_4_3
Base=$HOME/MGjobs
mkdir $Base

for (( i=1; i<=5; i++ ));
do

jobBase=$Base/job$i
cardBase=$jobBase/MG5_aMC_v2_4_3/testrun/Cards

mkdir $jobBase
cp -r $MGbase $jobBase

cd $jobBase

echo "" >> bout.log
echo "" >> berr.log

echo "#/bin/sh" >> MGscript.sh
echo "#PBS -N LNVjob$i" >> MGscript.sh
echo "echo 'seed: $i'" >> MGscript.sh
echo "printenv" >> MGscript.sh
echo "$jobBase/MG5_aMC_v2_4_3/testrun/bin/generate_events 0 run$i" >> MGscript.sh

cp $jobBase/MG5_aMC_v2_4_3/testrun/Cards/pythia_card_default.dat $jobBase/MG5_aMC_v2_4_3/testrun/Cards/pythia_card.dat
cp $jobBase/MG5_aMC_v2_4_3/Delphes/cards/PW_FCC_delphes_card.tcl $jobBase/MG5_aMC_v2_4_3/testrun/Cards/delphes_card.dat
sed -i "33s/.*/      $i       = iseed   ! rnd seed (0=assigned automatically=default))/" $jobBase/MG5_aMC_v2_4_3/testrun/Cards/run_card.dat

chmod +x MGscript.sh
qsub -e berr.log -o bout.log MGscript.sh

done

save it as MGbatch.sh, make it an executable with chmod +x MGbatch.sh, and run it with ./MGbatch.sh. This script will run 5 separate MadGraph instances simultaneously which each generate 10,000 parton level events which are then showered, hadronized, and matched with Pythia, and then run Delphes on the existing pythia.hep files to produce both root and lhco files using the specialized 100 TeV tcl Delphes card. Once all these jobs are done running, i.e., none of the jobs show up when you type qstat anymore, there should be delphes_output.root and delphes_root.lhco files in each of the Events/run folders.

Final Comments¶

This concludes the tutorial on how to perform distributed MadGraph + Pythia + Delphes simulations of a BSM FeynRules model on the titan cluster. In order to expand on this for your own research, you’ll need your own FeynRules UFO model folder. In order to make changes to run_card.dat or param_card.dat in a parallel manner, add extra sed commands into the MGbatch.sh script.

If you have any questions or problems with the above procedure, feel free to contact me.

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