Definition of Terms

Several terms used throughout the Physics Reference Manual have specific meaning within Geant4, but are not well-defined in general usage. The definitions of these terms are given here.

• process - a C++ class which describes how and when a specific kind of physical interaction takes place along a particle track. A given particle type typically has several processes assigned to it. Occaisionally ``process'' refers to the interaction which the process class describes.

• model - a C++ class whose methods implement the details of an interaction, such as its kinematics. One or more models may be assigned to each process. In sections discussing the theory of an interaction, ``model'' may refer to the formulae or parameterization on which the model class is based.

• Geant3 - a physics simulation tool written in Fortran, and the predecessor of Geant4. Although many references are made to Geant3, no knowledge of it is required to understand this manual.