#17 Review Breamstrahlung code

[Moritz Nadler]

The comments in GFMaterialEffects.h say that energyLossBrems uses the Bethe-Heitler formula with Migdal corrections but the noiseBrems uses the pure Bethe-Heitler model without any corrections. (From the code the most obvoious thing is that energyLossBrems does somthing different for e+ and e- while noiseBrems treats them equally.) So there is an incossistency between the two functions. Someone should do some researce if there more complex formulase for noiseBrems matching the corrections in energyLossBrems. Additionllay there is a strange factor of 1.44 multiplyed to the sigmaE2 (or 1.2 to sigmaE) that is not in the Bethe-Heitler formula for bremstrahlung variance I found in textbooks. Somewould should check where this factor is comming from or if it is just an error.

From the point of view of Belle II this does not have high proirty as tests with pGun e+/e- with typical Belle II energies produces p value diagrams that are more or less in agreement with what one would expect from a simple gaussion model for bremsstrahlung.

[Moritz Nadler]

Also the
defined(BETHE)
preprocesser commands should be replaced with something more transparent