Geant4 cross section read out fails

ROOT
1

I need to read out the cross section for compton scattering in water in geant4.9.5

I tried this:

  G4Element* H  = new G4Element("Hydrogen" , "H"  , z= 1.  , a= 1.01*g/mole   );
  G4Element* O  = new G4Element("Oxygen"   , "O"  , z= 8.  , a= 16.00*g/mole  );

  G4Material* H2O = new G4Material("Water", density= 1.000*g/cm3, ncomponents=2);
  H2O->AddElement(H, natoms=2);
  H2O->AddElement(O, natoms=1);
  // overwrite computed meanExcitationEnergy with ICRU recommended value    
  H2O->GetIonisation()->SetMeanExcitationEnergy(78.0*eV);

  G4double massSigma;
  G4EmCalculator emCalculator; 
  G4double tempDensity = H2O->GetDensity();
  G4ParticleDefinition* particle = G4ParticleTable::GetParticleTable()->FindParticle("gamma");
  
  for(G4double energyIT=1; energyIT<=10; energyIT+=1){
    massSigma = emCalculator.ComputeCrossSectionPerVolume(energyIT*keV,particle,"compt",H2O)/tempDensity;
    G4cout << G4BestUnit(massSigma, "Surface/Mass") << G4endl;
  }

All needed includes and variable definition is done. Compiling using gcc doesn’t return any errors.
Starting the simulation returns only ZERO values for cross section.

Output looks like this:

*************************************************************
 Geant4 version Name: geant4-09-05-patch-02    (22-October-2012)
                      Copyright : Geant4 Collaboration
                      Reference : NIM A 506 (2003), 250-303
                            WWW : http://cern.ch/geant4
*************************************************************

0 cm2/g
0 cm2/g
0 cm2/g
0 cm2/g
0 cm2/g
0 cm2/g
0 cm2/g
0 cm2/g
0 cm2/g
0 cm2/g

Does anyone have an idea what is wrong here?

2

Ok, this was definitely the wrong place for this question.

3

Yes, that’s a G4 one …