• DOI:10.1038/nature21717
• Corpus ID: 4456764

Background-free search for neutrinoless double-β decay of 76Ge with GERDA

@article{Agostini2017BackgroundfreeSF,
  title={Background-free search for neutrinoless double-$\beta$ decay of 76Ge with GERDA},
  author={Matteo Agostini and M. Allardt and A. M. Bakalyarov and M Balata and Igor I. Barabanov and L. Baudis and Christian Bauer and Enrico Bellotti and Sergey Belogurov and S. T. Belyaev and G. Benato and Alessandro Bettini and L. Bezrukov and Tobias Bode and Dorota Maria Borowicz and Viktor Brudanin and R. Brugnera and Allen Caldwell and C. Cattadori and A. I. Chernogorov and Valerio D’Andrea and Elizaveta V. Demidova and Nicola Di Marco and Assunta di Vacri and Alexander R. Domula and Evgeny Doroshkevich and V. G. Egorov and R. Falkenstein and O. Fedorova and K. Freund and N. Frodyma and Albert Gangapshev and A. Garfagnini and C. Gooch and P. Grabmayr and V. I. Gurentsov and K. Gusev and J. Hakenm{\"u}ller and Alex Hegai and Mark Heisel and Sabine Hemmer and Wilhelm Hofmann and M. Hult and L. V. Inzhechik and J. Janicsk{\'o} Cs{\'a}thy and Josef Jochum and Markus Junker and Vladimir Kazalov and Th. Kihm and I. V. Kirpichnikov and Andreas Kirsch and Alexander Kish and A. A. Klimenko and R. Kneissl and K. T. Kn{\"o}pfle and O. I. Kochetov and V. N. Kornoukhov and V. V. Kuzminov and Matthias Laubenstein and Antonio Di Lazzaro and V. I. Lebedev and Bjoern Lehnert and Hongbo Liao and Manfred Lindner and Ivano Lippi and A. V. Lubashevskiy and Bayarto Lubsandorzhiev and G. Lutter and Carla Macolino and B{\'e}la Majorovits and W. Maneschg and Eduardo Medinaceli and Michael Miloradovic and Rizalina Mingazheva and M. Misiaszek and P. S. Moseev and I. B. Nemchenok and Dimitrios Palioselitis and K. Panas and Luciano Pandola and Krzysztof Pelczar and Antonio Pullia and Stefano Riboldi and N. S. Rumyantseva and Cinzia Sada and Francesco Salamida and M. Salathe and Christopher Schmitt and Basil Schneider and Stefan Sch{\"o}nert and Jochen Schreiner and O. Schulz and Anne Kathrin Sch{\"u}tz and Bernhard Schwingenheuer and O. Selivanenko and E. A. Shevchik and M. V. Shirchenko and Hardy Simgen and Anatoly A. Smolnikov and L. Stanco and Laura Vanhoefer and A. A. Vasenko and A. Veresnikova and K. von Sturm and Victoria Wagner and Marc Walter and Annemarie Wegmann and Thomas Wester and Christoph Wiesinger and M. Wojcik and E. A. Yanovich and Igor Zhitnikov and S. V. Zhukov and Daniya Zinatulina and Kai Zuber and Grzegorz Zuzel},
  journal={Nature},
  year={2017},
  volume={544},
  pages={47-52}
}

• M. Agostini, M. Allardt, +113 authors G. Zuzel
• Published 1 March 2017
• Physics
• Nature

Many extensions of the Standard Model of particle physics explain the dominance of matter over antimatter in our Universe by neutrinos being their own antiparticles. This would imply the existence of neutrinoless double-β decay, which is an extremely rare lepton-number-violating radioactive decay process whose detection requires the utmost background suppression. Among the programmes that aim to detect this decay, the GERDA Collaboration is searching for neutrinoless double-β decay of 76Ge by operating bare detectors, made of germanium with an enriched 76Ge fraction, in liquid argon. After having completed Phase I of data taking, we have recently launched Phase II. Here we report that in GERDA Phase II we have achieved a background level of approximately 10−3 counts keV−1 kg−1 yr−1. This implies that the experiment is background-free, even when increasing the exposure up to design level. This is achieved by use of an active veto system, superior germanium detector energy resolution and improved background recognition of our new detectors. No signal of neutrinoless double-β decay was found when Phase I and Phase II data were combined, and we deduce a lower-limit half-life of 5.3 × 1025 years at the 90 per cent confidence level. Our half-life sensitivity of 4.0 × 1025 years is competitive with the best experiments that use a substantially larger isotope mass. The potential of an essentially background-free search for neutrinoless double-β decay will facilitate a larger germanium experiment with sensitivity levels that will bring us closer to clarifying whether neutrinos are their own antiparticles.