DDRec Manual

The reconstruction of particle tracks and clusters in an High Energy Physics detector requires information about the geometrical and material properties of the various tracking and calorimeter subdetectors. In general, a higher level view on the detector geometry is needed than for the purpose of simulating the detailed detector response with tools such as Geant4[4]. This higher level view typically involves the abstraction of detector layers, the corresponding measurement surfaces, accumulation of dead material along a path and conversion between cellIDs and positions. While in principle it is of course possible to extract this information from the detailed detector geometry model used for simulation, doing so would tightly couple the reconstruction code to the specific implementation of the simulation model. DDRec provides a generalized API for reconstruction that can be used to decouple the details of the $DD4hep$ [1] detector geometry model from the reconstruction algorithms.