What is the difference between Geant4 PAIPhot and Heed in Gardield++

Garfield++
1

Dear experts

I wonder what is the rough difference between PAIPhot model in Geant4 and Heed model in Garfield++

I heard that Heed consider the binding energy of electron where PAIPhot doesn’t, is that the only difference? Or I misunderstood something here.

Edit: PAIPhot will simulate photon absorption, Compton scattering, pair production for photons, where Heed only simulate photon absorption, right? Are they different in photon absorption process?

Thank you in advance

2

Hi,
I’m not a Geant4 expert so I can’t really comment on the PAIPhot model. Heed splits the photo absorption cross-section in contributions from each shell in order to be able to sample from which sub-shell the photoelectron was emitted, and it follows a (simplify) relaxation cascade (emission of Auger electrons or fluorescence photons). The tables of photo absorption cross-sections that are used by Heed are most probably different from the tables or parameterisations used in the Geant4 PAIPhot model.