I am trying to calculate the scintillation yield of a detector by summing the calculated light yield (given a known Birks value and using the eDep and dE/dx evaluated along the trajectory) after each step, but am a bit confused by the values for stopping power I am seeing.
My approach was to simply divide the energy deposited within a step by that step’s length to get the stopping power evaluated at that energy; however, this seems to depend heavily on the step size. If the step length is on the order of one micron or greater, the Geant4 stopping power values seem in rough agreement with the expected values from NIST ASTAR. However, lowering that step limit down to tens of nanometers results in large fluctuations (hundreds of MeV/mm) in dE/dx values that don’t seem physical.
Ordinarily, a step size of microns would be sufficient. However; there are some thin (sub-micron) layers of the detector, and so the particle just takes a single step in those volumes if the step limit isn’t lowered. So I was hoping someone would have some advice on how to correctly approach the issue of energy loss in thin layers.
The physics lists being used are EmStandard_option4 and StepLimiterPhysics.