(2 x 3 hour Labs)

In experimental particle physics there are very many particle collisions produced by particle accelerators and colliders. Each collision produces a very complex “photograph” captured by a 3D digital camera called particle detector. For scientific research about these fundamental ingredients of the Universe, these particles need to be 1) recorded, 2) analysed statistically and 3) the results be represented in graphical form to be made public in journal papers. Wouldn’t it be nice to have one program to satisfy all these needs?

The CERN laboratory has produced such a program and offers open access to it. It is now used in all particle physics experiments and starts to be used in nuclear physics and astroparticle physics as well. The software is called ROOT and is based on C++. In other words, it is a collection of C++ libraries that address all the three main goals. ROOT is possible thanks to the objectoriented features C++ of classes and inheritance. The data is stored in a very compact format, allowing for big data storage, both in a format for every collision (called tree), or on counts for the entire sample (histograms). All major types of statistical analyses are implemented. Finally, plots are saved to .pdf, .eps, .gif files. There is also an option to use ROOT from within Python, which simplifies the syntax of the commands. This is called PyROOT and is also used more and more.

This class is an introduction to ROOT to get you started in your research. The prerequisites are the knowledge from the SUPACOO class, but classes and inheritance will be discussed in this class. We will read a data tree in a visual mode and in code, will fill histograms from the tree, will fit a histogram to a function, will overlay different histograms to compare them (the standard in physics when the experiment is done in two different conditions and the results are compared) and save the results in graphical form. Depending on the time, we will go further into ROOT. We will also introduce PyROOT, and mention more advanced ROOT tutorials where you can study more.

Assessment: Continuous Assessment