Electromagnetic interaction model

We need to include an EM interaction model. Possible options are:

• EGS5
• EGSnrc (GPL licensed)
• EGS4 from CONEX
• The code used in H.E.S.S. that sbd. mentioned during the workshop

The first two options are continuations of EGS4 featuring more accurate cross-sections and often faster sampling procedures.

Hovever, all the EGSes share the disadvantage of being standalone codes with their own tracking, geometry, and variance reduction (i.e. sth. like thinning). We would need to put in some effort to rip out the routines (including proper initialisation) for single interactions and plug them in our main loop as module.

An alternative (likewise demanding considerable efforts) would be to write our own codes based on the descriptions in the various EGS manuals, starting with just the most important interactions.