Shooting neutrons on gold targets (1-1000 eV)

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Hi,

In my simulation I'm shooting Au targets with neutrons which can have energies between 1-1000 eV in order to evaluate what is called neutron self-shielding factor. Anyways... I'm basically comparing the number of neutrons absorbed in targets with different widths. The results I obtained are not within close agreement with experimental results. It seems to me that in the simulation a lower number of neutrons is absorbed therefore my curve is underestimated...

So I was wondering if some expert could have a look on my physics list and give me some hints on what I should do. I'm also uncertain about my material definition. I'm using Geant4 version 9.1 installed and I suppose the cross sections are taken from the G4NEUTRONHPDATA variable set in my environment but I'm not sure this is the right name to the variable used by geant4 to access the data.

I'm also uncertain about my material definition. Is the sintax below correct when thermal scattering is taken into account?

=============================================

// My Gold                                                                                
  G4Element* Gold =
  new G4Element("Gold","Au", 79.,196.97*g/mole);

  G4Material* MyGold =
  new G4Material("MyGold", 19.32*g/cm3, 1, kStateSolid, 300.0*kelvin, 1.0*atmosphere);
                                                                                  MyGold->AddElement(Gold,1);

==============================================

Here I attach the physics list file and a .eps file comparing my results and the experimental curve. Note the shape of the curve is due to doppler broadening and a huge number of Au resonances must be taken into account. Blue is data and red is simulation.

I have also some questions about the Au data sample too. Is it known how many Au resonances are included in Geant4? Is the S(\alph,\beta) model implemented in the 9.1 version of Geant4? Is there any validation of the G4HPNeutron package done with Au?

Thanks in advance, Franciole

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2009/03/04/16.35-10290-physics_list.cpp
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2009/03/04/16.35-74676-geant4_Au_width.eps