Investigation of ambient and μ-induced neutron background in LSM

A good particle candidate for Cold Dark Matter (CDM) is the supersymmetric neutralino or more generally a weakly interacting massive particle (WIMP). The expected interaction rate of WIMPs with the detector medium in the direct detection experiments is below 0.01 events/kg/day. This makes a good knowledge of the background conditions highly important, especially with ever increasing sensitivity of the detectors. One major component of the background is related to energetic neutrons induced by cosmic muons. However, the flux of low energy and thermal neutrons typically from (α,n) reactions in the rock surrounding underground experiments gives also valuable information about the overall environmental activity. Detailed studies carried out in the framework of the Edelweiss experiment are presented with first identification of muon-induced neutron candidates in Ge bolometers.