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Title: Results from phase I of the GERDA experiment

The GERmanium Detector Array Gerda at the Laboratori Nazionali del Gran Sasso of the INFN in Italy is an experiment dedicated to the search for the neutrinoless double beta (0νββ) decay in {sup 76}Ge. The experiment employs high purity germanium detectors enriched in {sup 76}Ge inside a 64 m{sup 3} cryostat filled with liquid argon. Gerda was planned in two phases of data taking with the goal to reach a half-life sensitivity in the order of 10{sup 26} yr. Phase I of Gerda was running from November 2011 until May 2013. With about 18 kg total detector mass, data with an exposure of 21.6 kg·yr was collected and a background index of 0.01 cts/(keV·kg·yr) was achieved in the region of interest. No signal was found for the 0νββ decay and a new limit of T{sub 1/2} > 2.1 · 10{sup 25} yr (90% C.L.) was obtained, strongly disfavoring the previous claim of observation. Furthermore, the 2νββ decay half-life of {sup 76}Ge was measured with unprecedented precision. Other results include new half-life limits of the order of 10{sup 23} yr for Majoron emitting double beta decay modes with spectral indices n = 1, 2, 3, 7 and new limits in themore » order of 10{sup 23} yr for 2νββ decays to the first 3 excited states of {sup 76}Se. In Phase II, currently in preparation, the detector mass will be doubled while reducing the background index by a factor of 10.« less
Authors:
 [1]
  1. Institute of Nuclear and Particle Physics, TU Dresden, Zellescher Weg 19, Germany thomas.wester@tu-dresden.de (Germany)
Publication Date:
OSTI Identifier:
22492678
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1686; Journal Issue: 1; Conference: MEDEX'15: Workshop on calculation of double-beta-decay matrix elements, Prague (Czech Republic), 9-12 Jun 2015; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ACCURACY; ARGON; CRYOSTATS; DOUBLE BETA DECAY; EXCITED STATES; GE SEMICONDUCTOR DETECTORS; GERMANIUM 76; HALF-LIFE; LIQUEFIED GASES; MASS; NEUTRINOS; SELENIUM 76; SENSITIVITY; SIGNALS