In Geant4, constructors constant some physic process and can be easily invoked, however, I don’t know how to changed the internal model for a existed constructors？ for example, change the model of multiple Coulomb scattering in G4EmLivermorePhysics.
In addition,how to achieve the function if I wanna to add process in a exit constructors？
Thanks very much.
we offer many PhysicsConstructors but usually recommend to start from G4EmStandardPhysics and G4EmStandardPhysics_option4. The first is our default do not focused on a concrete application, the second includes a set of “most accurate” EM physics models. The second configuration is our recommendation to achieve maximal accuracy of simulation but it is slower than the default.
Note, that in recent versions of Geant4 there is no principal differences between Opt0, Opt3, Liv, Pen, Opt4 results. Opt4 usually closer to data, other are not bad. Your choice between these constructors is the simplest what you can do. In most cases it is enough.
We provide also a feature when for specific G4Region you may redefine EM physics - there are corresponding UI commands. For me this would not be the first choice.
Thanks very much for your reply, now I copy the G4EmStandardPhysics.hh and G4EmStandardPhysics.cc to my local work director directly, although it is not a better choice, it can work if I want to change or delete a physical model.