Physics processes for optical photons

A photon is called optical when its wavelength is much greater than the typical atomic spacing, for instance when $\lambda \ge 10nm$

which corresponds to an energy $E\; \le 100eV$ . Production of an optical photon in a HEP detector is primarily due to:

1. Cerenkov effect;
2. Scintillation;
3. Fluorescence.

Fluorescence is taken into account in GEANT in the context of the photoelectric effect ( [PHYS230], [PHYS231]), but only above the energy cut CUTGAM. Scintillation is not yet simulated by GEANT.

Optical photons undergo three kinds of interactions:

1. Elastic (Rayleigh) scattering;
2. Absorption;
3. Medium boundary interactions.

• Elastic scattering
• Absorption
• Medium boundary effects