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GERDA detector: Neutrino physics

Are neutrinos really their own antiparticles? Why are they so light and what mass do they have? Scientists working on the GERDA experiment want to find out more about the properties of neutrinos.

Neutrinos are some of the most common particles in the universe. They are produced, for example, in the nuclear fusion taking place in the interior of stars, as well as in the Sun and during nuclear fission in power plants. Since they interact only via the weak force, they are extremely difficult to detect.

According to the present state of our knowledge, every known particle has an antiparticle with the opposite electric charge: anti-quarks, or anti-leptons (positron, anti-muon and anti-tau). As the neutrino is electrically neutral, it could be the odd one out here and be its own antiparticle. If the experiment can confirm this assumption, the researchers will have new starting points for gaining a better understanding of the physics of the universe.

The GERDA experiment

Installation of the lock system for Phase II of the GERDA experiment in a cleanroom at the MPP
Installation of the lock system for Phase II of the GERDA experiment in a cleanroom at the MPP (Photo: A. Griesch/MPP)

The GERDA experiment is investigating whether the neutrino is its own antiparticle. The search is on for so-called neutrinoless double-beta decay, which has never been observed before. One isotope which could exhibit this extremely rare radioactive decay is germanium-76. The experiment is therefore based on germanium detectors which have been enriched with this isotope.

Neutrinoless double-beta decay involves the conversion of two neutrons into two protons and two electrons. Two neutrinos are also released in this process, but they can annihilate each other – provided they are their own antiparticles. This decay therefore exists only if

  • neutrinos and their antiparticles are identical
  • and have a mass.

The GERDA experiment incorporates a total of 36 kilograms of detector material. This corresponds to around 1026 germanium-76 nuclei in total. With this number of nuclei, it should prove possible to detect this decay within a few years if its half-life is 1026 years or less.

Should GERDA measure a small number of the hypothetical and extremely rare decays, this would be a possible answer to the question: Why the universe contains matter, but no longer contains any antimatter – the key to our existence. Moreover, the physicists could draw conclusions about the mass of the neutrino.

Underground environment with extremely low radiation

Schematic diagram of the GERDA experiment: The germanium detectors are installed in a tank filled with noble gas
Schematic diagram of the GERDA experiment: The germanium detectors are installed in a tank filled with noble gas (Image: GERDA)

As neutrinoless double-beta decay is so rare, the GERDA experiment has to have the best possible protection against disturbing influences. It is therefore located in the Gran Sasso underground laboratory in Italy, where 1.4 kilometers of mountain rock shield it against cosmic radiation from space.

The germanium detectors are furthermore in an extremely clean environment: in a tank made of specially selected steel with a very low radiation rate which is filled with liquid argon. This vessel is in turn housed in a ten-meter-diameter tank filled with ultrapure water.

The GERDA collaboration has around 120 members from 16 institutes in six European countries, including the Max Planck Institutes for Physics (MPP) and Nuclear Physics. The GERDA Group at the MPP was responsible for constructing the cleanroom above the cryostat, and for developing and constructing the infrastructure used to lower the detectors into the argon tank, the so-called lock system.

Further information on the GERDA group

News releases


Scientists report an important milestone in the search for neutrinoless double beta decay (0vββ). As published in Nature, the GERDA experiment succeeded in reducing the radiation background to an extent that there are practically no disturbing signals any more. If the germanium detectors now measure...

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Is the neutrino its own antiparticle? How large a mass do neutrinos have? Scientists working on the GERDA experiment want to find answers to these questions. The first results of the second measurement phase, which began in December, were recently presented at the Neutrino 2016 conference in London.

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Stefan Schönert, Professor for Experimental Astroparticle Physics at the Technical University of Munich (TUM), has been named a Max Planck Fellow at the MPP, where he will do research in the area of dark matter and neutrino physics. The Fellow Program of the Max Planck Society (MPG) has the goal of...

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Group members

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Caldwell, Allen, Prof. Dr.

Director 529

Dharani Sundaresan, Sukeerthi

Student 361

Du, Qiang


Eck, Simon

Student 242

Fischer, Felix

Student 361

Gooch, Christopher

Engineering 242

Hayward, Connor

PhD Student 379

Kneißl, Raphael

PhD student 415

Krätzschmar, Thomas


Li, Kai Hong

Student 207

Majorovits, Béla, PD Dr.

Scientist 262

Plaul, Oliver

Student 371

Sala, Elena

Scientist 280

Schulz, Oliver, Dr.

Scientist 521

Schweisshelm, Barbara

Student 415

Vanhoefer, Laura

PhD Student 337

Zsigmond, Anna Julia, Dr.

Scientist 337

Events and meetings

Key publications

Production, characterization and operation of 76Ge enriched BEGe detectors in GERDA
GERDA collaboration
EPJC 75 (2015) 39

Results on Neutrinoless Double-β Decay of 76Ge from Phase I of the GERDA Experiment
GERDA collaboration
Phys. Rev. Lett 111 (2013) 122503

Results on ββ decay with emission of two neutrinos or Majorons in 76Ge from GERDA Phase I
GERDA Collaboration
Eur. Phys. J. C 75 (2015) 416
cover page of EPJC vol 75/9

Pulse shape discrimination for GERDA Phase I data
GERDA collaboration
Eur. Phys. J. C 73 (2013) 2583

The background in the 0νββ experiment GERDA
GERDA collaboration
Eur. Phys. J. C 74 (2014) 2764

The GERDA experiment for the search of 0νββ decay in 76Ge
GERDA collaboration
Eur. Phys. J. C 73 (2013) 2330