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T: Fachverband Teilchenphysik

T 109: Experimentelle Techniken der Astroteilchenphysik 2

T 109.4: Vortrag

Montag, 4. März 2013, 17:35–17:50, HSZ-101

Background suppression in Gerda Phase II and its study in the LArGe low background set-up — •Dušan Budjáš — Physik-Department E15, Technische Universität München, Germany

In Phase II of the Gerda experiment additional ∼20 kg of BEGe-type germanium detectors, enriched in ⁷⁶Ge, will be deployed in liquid argon (LAr) to further increase the sensitivity for the half-life of neutrinoless double beta (0νββ) decay of ⁷⁶Ge to >2·10²⁶ yr. To reduce background by a factor of 10 to the required level of <10⁻³ cts/(keV·kg·yr), it is necessary to employ active background-suppression techniques, including anti-Compton veto using scintillation light detection from LAr and pulse shape discrimination exploiting the characteristic electrical field distribution inside BEGe detectors. The latter technique can identify single-site events (typical for 0νββ) and efficiently reject multi-site events (mainly from γ-rays), as well as different types of background events from detector surfaces. The combined power of these techniques was studied for ⁴²K and other background sources at the low background facility LArGe. Together with extensive simulations, the information from tracking of the Phase II detector material exposure to cosmic rays and based on the background contributions observed in Phase I, the expected background level in Phase II in the region of interest at 2039 keV, the Q_ββ energy of ⁷⁶Ge, is estimated. The preliminary analysis shows that contributions from all expected background components after all cuts are in line with the goal of Gerda Phase II. This work is supported in part by the BMBF.