Tracker

A track detector or tracker is the part of a detector for measuring the trajectories of charged particles. Trajectory information is used for vertex finding as well as particle identification and momentum measurement, among other things. The tracker is usually the subdetector that is closest to the interaction point, where the collisions happen. In its design, the use of high-density materials is kept to a minimum to disturb the paths of the particles as little as possible and prevent energy loss of the particles via interaction with the tracker material.