LABORATORI NAZIONALI DI FRASCATI
Speaker: Riccardo Brugnera (Universita' di Padova & INFN, Sezione di Padova)
Neutrinoless double beta decay is a lepton-number violating process which is predicted by many extensions of the Standard Model.
It could be the key to understand the nature of the neutrino.
If observed, it would prove its Majorana nature and the half-life of the decay would be a direct measure of the yet unknown absolute scale of the neutrino-mass, assuming
the massive neutrino exchange as the dominant process.
The GERmanium Detector Array (Gerda) experiment at the INFN, Gran Sasso Laboratory, Italy, is searching for the
neutrinoless double beta decay of the isotope 76 Ge. High-purity germanium crystals enriched in 76 Ge are the source and the detector simultaneously. The key design feature of
Gerda is that detectors are deployed directly into an ultrapure cryogenic liquid (liquid argon), acting both as cooling medium and radiation shield against the external radiation.
After a major detector upgrade a second Phase (Phase II) of the experiment started in December 2015. Newly developed, custom-made BEGe-type germanium detectors made out of
enriched material were deployed in the setup, allowing for a superior background rejection by pulse shape discrimination. The background suppression was further improved thanks to an
active veto which detects the liquid argon scintillation light.
This presentation will summarize the basic concept of the Gerda design, the recent physics results from Phase II, the status and future perspectives of the neutrinoless double beta decay search using 76 Ge.