Given the toolkit nature of Geant4, a wide choice of physics processes and models is available. The choices use different physics modeling descriptions and offer different detail of physics modeling or . It is the choice of the user to decide how much detail in the physics modeling is needed, weighing the detail against cpu performance. A user can construct his own physics list, or use one of the physics lists offered in this site, or modify any of the offered physics lists.
In general, we expect the user to validate that a specific physics list does give reasonable results for his type of application. This will be most important for the application where the actual use case differs from the use case the list was created and tested for; examples of chnaged use case include a change in energy range of primary particles, use of different primary particles, or differing materials. We explicitly discourage to "blindy" try all physics lists available without regard to the use case at hand.
Physics Lists provided
Geant4 created a set of physics lists for typical use cases in a range of applications areas, see below. These lists are maintained, and in general evolve with new releases of Geant4 to include new options for processes, or to adapt to new validation.