dE/dx depending on StepSize


I have created my own application in which I record particles travelling through a sensitive detector. I store these particle’s energy depositions as well as their step lengths via the ProcessHit method. I have also implemented a G4StepLimiterPhysics which limits the step size of the particles travelling through my detector via the method SetMaxAllowedStep of G4UserLimits. What seems strange to me is that running the same event with different step size limits, does not yield the same dE/dx distribution, which I believe should not be the case.

Here you can see the difference in the dE/dx distribution for a 10 MeV electron propagating through liquid argon with a step size limit of 0.01 cm (left) and 1 cm (right).

Is there anything I am missing about how the step size limit works in Geant4?

Thanks in advance.


dEdx is a function of step limit. When your steps are longer energy loss is an integral of e- energy loss over energy of electron - initial and final energy on the step are different. These values fluctuate differently, secondary delta-electrons and gamma absorbed differently.