Angles and Dimuons

When protons collide, some of the energy of the collisions can become matter in the form of fundamental particles. These particles are extremely short-lived, so they never make it through the beam pipe to enter the ATLAS detector even if they travel at the speed of light. However, these short-lived fundamental particles transform into high energy, low mass particles. These particles have a longer lifetime which allows them to travel into the ATLAS detector. When a neutral particle from a collision decays, it can produce a muon and anti-muon. This is usually called a “dimuon event.” These events are seen in abundance in the ATLAS detector. We will examine such events to determine the opening angles between muons and anti-muons. The distribution of these opening angles tells us about the parent particles from which the dimuon events came.