Traditionally, underground experiments estimate their neutron backgrounds using extensive simulation normalized to a handful of events in their well-shielded target mass. This leads to large error bars and systematic uncertainties between technologies. A better strategy is to choose a few experiments which are uniquely sensitive to aspects of CMINB and use them to improve the physics and implementation of the simulation package(s) used by all experiments. The current status of these experiments is outlined below.
The two simulations in general use by the physics community are Geant4 [12–13] and FLUKA [14–15]. Geant4 is a C++ based toolkit of physics processes, geometry constructors and processing methods used to transport charged particles through matter. It is written, maintained, and validated by the Geant4 collaboration, which consists of high-energy physicists, space scientists, medical physicists and software engineers. The origin of FLUKA (FLUktuierendeKAskade) goes back to 1962 in the context of understanding shielding requirements for a new proton accelerator at CERN. FLUKA is an official project supported by CERN and INFN. It is a fully integrated particle physics Monte Carlo simulation package based on micro-physics models which are benchmarked and tuned against experimental data.
[Geant4] S. Agostinelli, et al. (the Geant4 collaboration), Nuclear Instrumentation Methods A 506 (2003) 250; J. Allison, et al. (the Geant4 collaboration), IEEE Transactions on Nuclear Science 53 (2006) 270.
[FLUKA] A. Ferrari, P.R. Sala, A. Fassò, and J. Ranft, FLUKA: a multi-particle transport code, CERN-2005-10 (2005), INFN/TC_05/11, SLAC-R-773; G. Battistoni, et al. The FLUKA code: Description and benchmarking, American Institute of Physics Conference Proceedings 896 (2007) 31.
What did we learn about Depth and Uncertainties remaining? List and prioritize needs for the future - what bkgd experiments and sims are needed.