The event display MINERVA

The electronic signals that are recorded by the detectors during a collision can be transformed into event displays. To visualize these, we use the program MINERVA. Before you can work with this program you should learn which possibilities and functions it has that are important for our analysis.



First, start the program MINERVA (If you are a participant of the International Masterclasses you can start the program directly from DVD. Otherwise you should firstly download the program here, unzip it secondly and finally start it.

Anyway, the program should look much like the first picture in the picture gallery. Use the following gallery to get some insight into the functions of the MINERVA program! Try these settings inside the program parallel.



  • This picture shows the start view of the program MINERVA with the two windows ATLANTIS CANVAS (red frame), which provides different visual detector views of the event, and the graphical user interface ATLANTIS GUI (green frame), which controls adjustments and has additional information about the event.
  • This picture shows the CANVAS window. It visualises the event. Thereby it is not shown as three-dimensional but rather displayed as two-dimensional projections. In the upper left corner (with a red frame), one can see the detector view with the view along the beam axis – the so-called cross-sectional view - and below (with a blue frame), there is the view from the side – the so-called side view. The display in the upper right corner (yellow frame) is used to distinguish the applications of energy of the individual particles better. Their positions are plotted in a plane that represents the unwound detector surface. The heights of the towers indicate how much energy is deposited at each location. Every event has a title that can be read at the top of the window (green frame).
  • The different detector shells are illustrated with different colours in the cross-sectional view as well as in the side view. The inner detector is grey, the electromagnetic calorimeter green, the hadronic calorimeter red, and the muon chamber is blue.
  • The paths of electric charged particles are displayed by coloured tracks in the event display. They were reconstructed after the measurement. The colour of one track is encoded by a relevant physical quantity, the transverse momentum - the momentum of a particle at right angles to the beam pipe. The legend will help you in decoding. In this enlarged depiction you can see two tracks, one red (high transverse momentum) and one blue (low transverse momentum) track.
  • Connecting energy deposits in the calorimeters to specific tracks in the inner detector is not always easy. In this event one can see that there isn't a smooth transition from the tracking detector to the calorimeters. Here, you actually have to estimate. Energy deposits are displayed as yellow cell entries in both the electromagnetic and the hadronic calorimeter as well.
  • Besides neutrinos, muons are the only particles that can make it from the collisions to the outer detector area. They are detected within the muon chambers (displayed blue). If a muon hits a chamber, information about its path through the chamber is displayed by an orange track. If a muon hits several chambers, one can determine its way through the chambers by combining the orange tracks.
  • You will use the GUI window mainly to load files into the program (via File – Read Event Locally; green frame). The packed file to be read consists of several files each of which has saved one event. By selecting the Previous or Next arrows in the upper right menu (brown ellipse), you can advance or move back to individual events. With the help of the tool bar (red frame) you are able to change the view of the events (by e.g. zoom in and out). Information of particles are accessible as well. These are displayed inside the information box (blue frame). You can also define special selection criteria for the particles of an event shown in the event display via the 'cuts' card (yellow frame).
  • There is much going on inside this event. You can see many tracks. Not all of them are interesting. Particles with high transverse momentum (momentum of a particle that is at right angles (perpendicular) to the beam pipe) are of interest and can be selected.
  • In the GUI window you can use the "Cuts" card to show only particles with transverse momenta above a specified value in the event display. Therefore, you only have to enter a value for this transverse momentum in the input field (yellow frame: Try it with 10 GeV!) and confirm it via the enter key. Make also sure that the little box left beside the input field is ticked. Go to the next picture in order to see the result of that setting.
  • Now it looks more clearer. In order to get information about the remaining particles you can use the finger pick symbol from the tool bar (red frame). By clicking on one particle track not only the colour changes. Also detailed data is displayed inside the information box. You will find it on the next picture.
  • Pay attention to the blue frame with information about the chosen particle. And one can do even more with MINERVA. For example: measure angles. See on the next picture …
  • The program is able to measure the angle between two particle tracks in the plane at right angles to the beam pipe. (This plane is called transverse plane.) To do so you hold the “P” key down on the keyboard before selecting the two tracks. The angle is displayed in the information window in degree and radian (blue frame).


Now, find out how you can identify particles with the help of MINERVA.