Measuring External Sources of Background (R\&D) at Homestake

Measuring external sources of radioactivity at the DUSEL site is the key to success in low-energy neutrino and dark matter (WIMP searches) experiments. Natural radioactivity can be measured using germanium and NaI detectors. Muon-induced neutrons and (a,n) neutrons will be measured utilizing liquid scintillators and germanium detectors through the 72Ge(n,nxe) reaction. External sources of background, particularly fast neutrons and cosmogenic radioactivity from muon-induced processes, are background matter that must be eliminated for underground experiments in pursuit of double beta decay, WIMPs, and oscillations of low-energy neutrinos. However, muon-induced neutron production rates with heavy elements, such as lead and copper, are not well understood. The discrepancy between the measurements and FLUKA simulations is as large as about a factor of 3. This discrepancy needs be understood for the muon- induced fast neutron production rate in lead and copper, which are the most popular materials for shielding underground experiments. We propose an experiment at 300-ft level to measure the muon-induced fast neutron production rate in different targets.