Problem 2090

Summary: No backward scattering from G4eSingleCoulombScatteringModel
Product: Geant4 Reporter: Takao Kitaguchi <takao.kitaguchi>
Component: processes/electromagnetic/standardAssignee: Vladimir.Ivantchenko
Status: RESOLVED FIXED    
Severity: minor    
Priority: P4    
Version: 10.4   
Hardware: All   
OS: All   

Description Takao Kitaguchi 2018-09-10 09:20:19 CEST 
There is no backward scattering from the G4eSingleCoulombScatteringModel class. At the 210-th line in G4eSingleCoulombScatteringModel (see the below link), the scattering angle is calculated by

 G4double cost = sqrt(1.0 - sint*sint);

 http://www-geant4.kek.jp/lxr/source/processes/electromagnetic/standard/src/G4eSingleCoulombScatteringModel.cc#L210

Therefore, cost is always positive, corresponding to the forward scattering. I think that the correct calculation is simply

  G4double cost = cos(z1);
Comment 1 Vladimir.Ivantchenko 2018-09-26 12:11:27 CEST 
Hello,

thank you very much for the detailed analysis of the problem. It is fixed now and the fix will be available for the next public release of Geant4.

Vladimir