The goal of this exercise is to get acquainted with a particle physics measurement, analyzing proton-proton collisions produced by the Large Hadron Collider (LHC) and recorded by the Compact Muon Solenoid (CMS) experiment.
The measurement to be performed is the top quark pair production cross section in proton-proton collisions at the CMS experiment. A recommended reading is this CMS paper at 8 TeV.
The code is executed in the Ubuntu operating system using the ROOT data analysis framework developed at CERN. To work in the Ubuntu operating system using ROOT regardless of your operating system (such as macOS or Windows) we will work with Docker containers. A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another. A Docker container image is a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings.
The setup below is valid for macOS and Unix. To proceed with Windows please follow the TOP_XS_Windows.pdf instructions.
Install XQuartz. [macOS]
https://www.xquartz.org/
Install Docker Desktop.
https://www.docker.com/get-started/
Download the ROOT Ubuntu image from Docker Hub.
docker pull calderona/root-ubuntu16
Check your Docker images.
docker images
If you want to delete some image.
docker rmi calderona/root-ubuntu16
Needed for display. [macOS]
ip=$(ifconfig en0 | grep inet | awk '$1=="inet" {print $2}')
export DISPLAY=:0
/opt/X11/bin/xhost + $ip
Download the HEPAnalysis code. [Unix]
wget https://calderon.web.cern.ch/calderon/codes/HEPAnalysis.tgz
Download the HEPAnalysis code. [macOS]
curl -L https://calderon.web.cern.ch/calderon/codes/HEPAnalysis.tgz > HEPAnalysis.tgz
Extract the HEPAnalysis code.
tar -xvzf HEPAnalysis.tgz
Run the Docker image.
userhome will point to $FULLPATH/HepAnalysis.
docker run --rm -it -v $FULLPATH/HEPAnalysis/:/userhome -v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=$ip:0 calderona/root-ubuntu16 bash
Jonatan's laptop.
docker run --rm -it -v /Users/Pandora/HEPAnalysis/:/userhome -v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=$ip:0 calderona/root-ubuntu16 bash
The physics behind this exercise, together with an introduction of some high energy concepts such as purity or trigger efficiencies, are presented in CMS.pdf. The provided HEPAnalysis code is also briefly explained here.
- Read CMS.pdf.
- Execute the provided code out-of-the-box and look at the produced histograms.
- Open the provided code and modify it to produce an additional histogram.
This exercise has been developed by Alicia Calderón based on a CMS HEP tutorial by the International Particle Physics Outreach Group (IPPOG). The data provided for the analysis is CMS open data.