Multiple scattering and step length for MeV-scale electrons


I’m simulating, using Geant4 10.6.p01 (G4EmStandardPhysics_option4 physics list), the propagation through high-pressure xenon (10 bar) of electrons of 1–2 MeV of energy. I’m using the G4StepLimiter process to limit the maximum step length of the electrons to 1 mm to get finely segmented tracks. This appears to have a non-negligible impact on the simulation of multiple scattering. See, for example, the average scattering angle as a function of the kinetic energy of the electron for events in which the maximum step length has been limited to 1 mm compared to the case in which it hasn’t been limited:
cosine_kinetic_profileX.pdf (16.0 KB)

This difference has a direct impact on the volume extent of the tracks (not the total track length):
volume_hist.pdf (15.0 KB)

The step-limited results happen to be closer to our data. Therefore, I was wondering whether this result is in agreement with what should be expected from Geant4’s msc model. If that is the case, can I get higher precision limiting the maximum step length even more?


hello,could you tell me how to set the step length limit?after watching your images,I guess that maybe i encounter the same question.


what is the parameter “cosine” , how it is computed? For me both blue and red curves are not clear. The most strange thing is that blue and red agree at 0.1 MeV and 2.5 Mev but disagree in between. So, you need to double check what you score.

For comparisons I would also suggest to try out Opt3 EM physics - would results be similar to Opt4?