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.

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:

• Geant4.9.3: without muon-nuclear turned on
• Geant4.9.3+: this is a version of Geant4 which is Geant4.9.3 with the “shielding” physics list (implemented in v4.9.4) and a new muon-nuclear interaction (to be implemented in v4.9.5) have been backported
• FLUKA 2011.2.5

For the scintillator material composed of C<sub>9</sub>H<sub>12</sub> which has density 0.887 g/cm<sup>3</sup> which is similar to the Borexino scintillator, several plots have been produced.