Introduction to GEANT4

Two kinds of base physics list classes are available for users to derive from: <span style="color:#ff0000"> G4VUserPhysicsList </span> and <span style="color:#ff0000"> G4ModularPhysicsList </span>. There exists also pre-packaged physics list.

You can use the class <span style="color:#ff0000"> G4VUserPhysicsList </span> if you want to use simple physics lists. <span style="color:#ff0000"> G4VUserPhysicsList </span> has three methods:

Simple example of <span style="color:#ff0000"> MyPhysicsList </span> derived from <span style="color:#ff0000"> G4VUserPhysicsList </span>:

GEANT4 provides a variety of physics processes. These processes are decoupled from one another and the user can select those processes which are relevant to his/her simulation. There are seven categories of processes provided by GEANT4:

where the method ConstructEM() is defined as:  

In methods ConstructEM() and ConstructGeneral() to each particle you have to assign the corresponding physics processes they are involved in. This is a link to the physics processes available for each particles [http://geant4.cern.ch/support/proc_mod_catalog/particles/ Physics Process for Particles].     

A realistic physics list has a lot of different physics processes. Therefore it is better to define a new class <span style="color:#ff0000"> G4VModularPhysicsList </span> derived from <span style="color:#ff0000"> G4VUserPhysicsList </span> where you can group the physics processes into EM physics, hadronic physics, optical physics etc. The method AddTransportation() is called automatically for all particles. Simple example of <span style="color:#ff0000"> G4VModularPhysicsList </span>: