For the outreach programme LHCb Masterclass students from secondary schools are invited to analyze a sample of D0 → K− pi+ decays as collected from the LHCb experiment to measure the lifetime of the D0 meson.
The data used for this exercise are public and can be obtained from the Open Data portal of CERN.
In this tutorial we repeat the analysis designed for the LHCb Masterclass, using Python and ROOT in order to show how the most common operations in data analysis can be performed within such a framework.
We will take the opportunity to apply some machine learning, this is not part of the original excercise, but it is worth to include an example on how to use Keras and Tensorflow to separate signal and background. This is not a lecture on machine learning: several basic and important aspect of a machine learning problem are ignored here, for example we do not split the data in training and test samples. From a software perspective, it should be trivial to extend the example to include a more careful treatment of the neural network training and application.
The website of the LHCb International Masterclass, where the excercise is shortly explained can be found at this link.
Static jupyer notebook: https://github.com/landerlini/MLINFN-TutorialNotebooks/blob/master/LHCbMasterclassExplained.ipynb
Requirements
To run this exercise you will need python3, tensorflow 1.x and PyROOT for python3.
Contents
With this tutorial, we will introduce the following topics:
- Download data with jupyter via http
- Exploring a dataset with pandas
- Exploring a dataset with matplotlib
- Obtaining high quality plots with ROOT
- Modelling the data with RooFit
- Perform a per-event subtraction of the background using sPlot
- Training a simple neural network on nTuple data with keras
- Evaluate the performance of the trained algorithm
- Apply the neural network to data
- Studying systematic effects induced by the neural network