In this exercise we will be looking at Z0 boson decays and measuring the mass of the particle by examining it's decay products. This is necessary because the Z0 boson decays too quickly to allow us to measure it directly. Here we make use of the invariant mass introduced on the last page. By conserving energy and momentum we find that the rest mass of a decaying particle is equal to the invariant mass of it's decay products.
The applet on the right of your screen is a simulation of a detector in the
D0 Experiment. In the detector you can see an 'event', showing
the tracks of the particles produced in a Z0 boson decay. You can cycle through the available
events with the controls at the bottom of the applet. By adding each decay particle to the
invariant mass of the system and then adding the invariant mass of several
systems (one per event) to the graph you will find the mass of the Z0
boson at the peak. The points on the graph are spread around the mass of the Z0
boson due to experimental error in the data provided.