I am simulating a novel PET scanner composed of multiple layers of pixel silicon detectors intercalated with absorber bismuth layers. For this I am using the AllPix^2 framework.
My back-to-back photon pair (each with ~511 keV) comes from a positron source.
For completeness, I use the FTFP_BERT_LIV physics list.
My problem is that I see photons being produced (in the absorber layers) via the phot production process (from one of the photons from the positron annihilation). I attach a screenshot of such event with Tracks and Particles information (and I tried to illustrate the relationship between the particles/tracks by using different colours).
Sometimes, as in the event attached, I see a photon and an electron (both from the same photon and phot production process) created at slightly different times. Sometimes I only see a photon, and other times I have only the electron created (what I would expect).
My (Geant4 naive) question: Where is this photon from the photoelectric effect coming from? Is fluorescence also simulated?
Thanks for the help!