Study of the electromagnetic background in the XENON100 experiment
  The XENON100 experiment, located at the Laboratori Nazionali del Gran Sasso
(LNGS), aims to directly detect dark matter in the form of Weakly Interacting
Massive Particles (WIMPs) via their elastic scattering off xenon nuclei. We
present a comprehensive study of the predicted electronic recoil background
coming from radioactive decays inside the detector and shield materials, and
intrinsic contamination. Based on GEANT4 Monte Carlo simulations using a
detailed geometry together with the measured radioactivity of all detector
components, we predict an electronic recoil background in the WIMP-search
energy range (0-100 keV) in the 30 kg fiducial mass of less than 10e-2
events/(kg-day-keV), consistent with the experiment's design goal. The
predicted background spectrum is in very good agreement with the data taken
during the commissioning of the detector, in Fall 2009.
