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T: Fachverband Teilchenphysik

T 109: Niederenergie-Neutrinophysik/Suche nach Dunkler Materie 4

T 109.3: Vortrag

Dienstag, 28. Februar 2012, 17:20–17:35, ZHG 103

α-Background characterization for the GERDA experiment — •Neslihan Becerici-Schmidt — Max-Planck-Institut für Physik, München

The Germanium Detector Array - GERDA - is a neutrinoless double beta (0νββ) decay experiment, that aims to advance our knowledge on the nature and properties of neutrinos. The current limits on the half-life of 0νββ-decay are in the order of 10²⁵ years. In order to increase the sensitivity on the half-life with respect to past experiments, the background rate in the region of interest (around Q_ββ) needs to be reduced. GERDA started data-taking with the full set of phase-I detectors in November 2011. Understanding of the background is of major importance to further mitigate the background for GERDA phase-II.

An analysis of candidate α-events in the GERDA background spectrum is presented. Events with energies above the highest prominent γ-line from natural radioactivity are assumed to be dominantly due to α-decays on the surface of the detectors. These first pass through the dead layers on the surfaces, losing part of their energy. The α-energy deposited in the active volume may be close to the Q_ββ. A model, based on the assumption that all high energy events in the spectrum come from surface α-decays, is compared with data. A very good agreement between the model and the data is found. The background contribution from α’s in the region of interest is estimated.