LHCb Event display

The LHCb Event Display was made for educational purposes at the European Organization for Nuclear Research, CERN in Geneva, Switzerland. The project was implemented as a stand-alone application using C++ and ROOT, a framework developed by CERN for data analysis. This paper outlines the development and architecture of the application in detail, as well as the motivation for the development and the goals of the exercise. The application focuses on the visualization of events recorded by the LHCb detector, where an event represents a set of charged particle tracks in one proton-proton collision. Every particle track is coloured by its type and can be selected to see its essential information such as mass and momentum. The application allows students to save this information and calculate the invariant mass for any pair of particles. Furthermore, the students can use additional calculating tools in the application and build up a histogram of these invariant masses. The goal for the students is to find a $D^0$ particle in the event, which decays into the two different particles selected by the students. The $D^0$ is distinguished from background by the fact that its tracks come from a secondary vertex, separated from the primary proton-proton collision. The menu bar in the Event Display has many viewing options, including projections and zooming options, which can make this task a bit easier. Even if a student doesnt find all the decays successfully, they will be able to complete the exercise and get a meaningful set of results. The application also offers detailed instructions and inline help available in five languages: English, Italian, French, German and Romanian.