How can I modify the muon's charge to do fractional charges simulation?

Hi all,

I’m doing some study about Fractional charged particles.

Now I want to processing the MC simulation with Geant4, but I didn’t find a fractional charged particle in particle list. Then I tried to modify the charge of muon, but It didn’t work, I modified the source code like this:

I wonder weather I can modify the muon’s charge to do this simulation or I need to create a new fractional charged particle.

Thanks for your help!


in general it is not a good idea to modify parameters of standard particles. I would suggest to have a look into $G4INSTALL/examples/extended/exoticphysics

There are two examples so far - magnetic monopole and dark matter photon. In both we suggest that a new particle is created by user, corresponding physical processes are added on top of physics for ordinary particles.



Thanks for your instruction, I’ve successfully created a fractional charged particle and it can be used in my model.

The PhysicsList in my model uses the G4VModulePhysicsList(), so I need to write a FcpPhysicsList for my fcp particle which was derived from G4MonopolePhysics.

I set the mass to 120 MeV, and charge to 0.66 e. it worked well with G4hMultipleScattering and G4hIonisation. I also want to add the Bremsstrahlung, but it didn’t work.

Thank you for your help!


bremsstrahlung and pair production have non-zero cross sections above 1 GeV.
Order of processes are a bit different:

(new G4hMultipleScattering, -1, 1, -1)
(new G4hIonisation, -1, 2, 1)
if needed:
(new G4hBremsstrahlung, -1, -1, 2)
(new G4hPairProduction, -1, -1, 3)



When I added the process as you wrote, it still didn’t work whether the mass is above 1GeV or still 120MeV. but when I remove the Bremsstrahlung process, it works well.

it seems like the three parameters matters when adding the processes. I don’t know what is the different, and what to set if I want to simulate a 120 MeV particle with Bremsstrahlung?

(There are some mistake in the last version reply, so I revised it.)

Thank you!

I’m looking forward to your replay!