Germanium Detector Array
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The GERmanium Detector Array (GERDA) experiment is searching for neutrinoless double beta decay(0vββ) in Ge-76 at the underground Laboratori Nazionali del Gran Sasso (LNGS). Neutrinoless beta decay is expected to be a very rare process if possible. The collocation predicts less than one event each year per kilogram of material. Background shielding is required to detect any rare decays.
The experiment uses high purity enriched Ge crystal diodes as a decay source and particle detector. The detectors from the HdM and Igex experiments were reprocessed and used in GERDA. The detector array is suspended in a liquid argon cryostat lined with copper and surrounded by an ultra-pure water tank. PMTs in the water tank and plastic scintillators above detect and exclude background muons.
Results
Phase I collected data November 2011 to May 2013, with 21.6 kg·yr exposure, obtaining a 0vββ 90% CL half-life limit:
. This limit can be combined with previous results, disfavouring the Heidelberg-Moscow experiment claim. A double beta decay half-life was also measured: T2vββ = (1.84+0.14−0.10)·1021 yr.
Phase II will have additional enriched Ge detectors and reduced background.
Publications
- Results on neutrinoless double beta decay of 76Ge from GERDA Phase I, Phys. Rev. Lett. 111 (2013) 122503
- Measurement of the half-life of the two-neutrino double beta decay of 76Ge with the GERDA experiment, Phys. G: Nucl. Part. Phys. 40 (2013) 035110
- The GERDA experiment for the search of 0νββ decay in 76Ge, Eur. Phys. J. C 73 (2013) 2330