Etude de bruit de fond induit par les muons dans l'expérience ...

tel-00724955, version 1 - 23 Aug 2012
Investigation of the muon-induced background of the EDELWEISS-II experiment
The EDELWEISS experiment aims to detect WIMPs, weakly interactive massive
particles, which could possibly amount for all or part of the dark matter in
the universe. It measures the energy released by nuclear recoils produced by the
elastic collision of a WIMP in an ordinary matter target. Due to the very small
interaction cross-section of WIMP with nucleons, which leads to an extremely low
expected event rate (< 1 event/kg/year), and due to the relatively small deposited
energy (< 100 keV), the nuclear recoil signal of WIMP events can be mimiced by
neutrons coming from natural radioactivity or induced by muons. The present work
is devoted to study the muon-induced background. Performances of the muon veto
of the EDELWEISS-II experiment are presented and detection of muons and showers
discussed. The first muon veto-bolometers coincidences has been performed on
two 4-month physics runs in 2007 and 2008 and leads to a result of 0.043 ± 0.015
coinc/kg/d for a recoil energy ER