Gamma and neutron background in the Edelweiss-II dark matter experiment

Abstract

The Edelweiss-II collaboration has completed a search for WIMP dark matter using 400-g cryogenic Ge detectors and 384 kg-d of effective exposure. The next phase aims to probe the range of spin-independent WIMP-nucleon cross-sections between 10−8 and 10−9 pb. We present the study of gamma and neutron background coming from radioactive decays in the set-up and shield materials based on GEANT4 Monte Carlo simulations combined with measured radioactivity levels of all components. The results of these background studies have been useful to design the changes in the Edelweiss set-up to further reduce the background events in the next phase of the experiment.