The calorimeter is 82 layers of: [ 14mm of G4_Fe + 3mm of G4_PLASTIC_SC_VINYLTOLUENE ]
Using the FTFP_BERT physics list, as is set by default on the example, I tried testing the response to electrons and charged pions at energies from 1 to 100 GeV.
The energy deposited by electrons in the scintillator volumes was consistently less than that for pions. This is unexpected, as Fe-Sci calorimeters should be undercompensating, and these results seem to indicate an overcompensating calorimeter (e/pi<1).
Is there any reason for the FTFP_BERT physics list in the B4 example giving such underestimated values for electrons in the scintillator?
Not exactly sure what you mean here. For a Geant4 simulation the pion rest mass (and subsequent muon decays) will mean that more energy is always deposited than for an electron for the same kinetic energy especially with such thin layers.
B4 as is does not model the optical physics that is probably very important to your readout. This includes light quenching from the differing LET which will be very large for the pion relative to the electron. It will also not include the visible light emission and absorption in a photodetector readout.
Optical physics packages are included in Geant4 but they are not enabled by default and will require a bit more work to match the specifics of your setup. Here is a good place to get started if you want to model optical physics.
The goal with this simulation is to obtain the energy deposited in the scintillator before any optical considerations, though they are definitely important for the readout and signal response.
The pion rest mass (~135 MeV) is still not enough to account for the difference observed. At 50 GeV, electrons are depositing on average 8% less energy in the scintillator than charged pions, while the rest mass would only account for less than 0.3%. This is ignoring the effects of “invisible” energy from hadronic interactions with the material, which result in pions depositing 15% less energy in all the calorimeter volume.
The problem I am seeing is that the electrons deposit more energy in iron and less in the scintillator, when compared with charged pions.