A study is ongoing to try to understand the specific differences between FLUKA and Geant4 simulations. Comparison to data are pursued wherever possible, although data is difficult to produce and not very abundant at present. This page reflects the state of the comparison as it existed in April 2013. This includes what was presented at the Low Radiation Techniques (LRT) conference in April 2013 at Gran Sasso.

It is important in such a study to be very specific about what physics models are involved in simulations. Typically this is stated through version numbers of either Geant4 or FLUKA. Formally this is not enough by itself for Geant4 since the physics list is modular and can be changed even within one compiled versions. For now a simple specification of the versions used in this page are included, to be updated and made more specific later:

• Geant4.9.5
• FLUKA 2011.2 patch level 17 (Dec 2012)

Several of the more important plots can be viewed below in separate sections and additional plots are available here.

As muons propagate through a cylindrical volume they begin creating neutrons and eventually the flux through the cylindrical area comes to constant. This means in the first small percentage of the cylinder the flux is increasing and after that one can reliably extract the flux. Below we plot the integrated flux (over the whole 10m sensitive cylinder) as a function of energy.

for Borexino scintillator (C9H12 at 0.887 g/cm^2) we plot the integrated flux as a function of neutron energy for several muon primary energies

for water we plot the integrated flux as a function of neutron energy for several muon primary energies

for calcium carbonate (CaCO_3) we plot the integrated flux as a function of neutron energy for several muon primary energies NOTE: Anthony found an error he made in material definition wherin Ca was being basically replaced by Na, working out new plots now…

UPDATE: There was an error made by Anthony in the material definition as per the above. The plot below shows the updated CaCO3 plots which display better agreement which no longer displays a clear resonance neary 1 - 2 keV. This resonance was found to be due to a wide Na-23(n,g) resonance.

for natural iron we plot the integrated flux as a function of neutron energy for several muon primary energies

for natural lead we plot the integrated flux as a function of neutron energy for several muon primary energies

UPDATE: A normalization problem was found in the FLUKA wherein all the curves were replaced with the 280 GeV versions, below is the new simulation result, which matches very well in integral but the shape is still very discrepant and needs to be investigated.