Eur. Phys. J. C (2015) 75: 416
https://doi.org/10.1140/epjc/s10052-015-3627-y

Regular Article - Experimental Physics

Results on decay with emission of two neutrinos or Majorons in Ge from GERDA Phase I

GERDA Collaboration

¹ LNGS, Assergi, Italy
² INFN Laboratori Nazionali del Gran Sasso and Gran Sasso Science Institute, Assergi, Italy
³ INFN Laboratori Nazionali del Sud, Catania, Italy
⁴ Institute of Physics, Jagiellonian University, Cracow, Poland
⁵ Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Dresden, Germany
⁶ Joint Institute for Nuclear Research, Dubna, Russia
⁷ Institute for Reference Materials and Measurements, Geel, Belgium
⁸ Max-Planck-Institut für Kernphysik, Heidelberg, Germany
⁹ Dipartimento di Fisica, Università Milano Bicocca, Milan, Italy
¹⁰ INFN Milano Bicocca, Milan, Italy
¹¹ Dipartimento di Fisica, Università degli Studi di Milano e INFN Milano, Milan, Italy
¹² Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia
¹³ Institute for Theoretical and Experimental Physics, Moscow, Russia
¹⁴ National Research Centre “Kurchatov Institute”, Moscow, Russia
¹⁵ Max-Planck-Institut für Physik, Munich, Germany
¹⁶ Physik Department and Excellence Cluster Universe, Technische Universität München, Munich, Germany
¹⁷ Dipartimento di Fisica e Astronomia dell‘Università di Padova, Padua, Italy
¹⁸ INFN Padova, Padua, Italy
¹⁹ Physikalisches Institut, Eberhard Karls Universität Tübingen, Tübingen, Germany
²⁰ Physik Institut der Universität Zürich, Zurich, Switzerland
²¹ Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA
²² Moscow Institute of Physics and Technology, Moscow, Russia
²³ International University for Nature, Society and Man “Dubna”, Dubna, Russia

^* e-mail: gerda-eb@mpi-hd.mpg.de
^** e-mail: grabmayr@uni-tuebingen.de

Received: 9 January 2015
Accepted: 18 August 2015
Published online: 9 September 2015

Abstract

A search for neutrinoless decay processes accompanied with Majoron emission has been performed using data collected during Phase I of the GERmanium Detector Array (GERDA) experiment at the Laboratori Nazionali del Gran Sasso of INFN (Italy). Processes with spectral indices were searched for. No signals were found and lower limits of the order of 10 yr on their half-lives were derived, yielding substantially improved results compared to previous experiments with Ge. A new result for the half-life of the neutrino-accompanied decay of Ge with significantly reduced uncertainties is also given, resulting in  yr.