Josef Jochum - Double Beta Decay and Lepton Number Violation

Neutrino masses are suprisingly small compared to the mass of all other fermions. An interesting possibility to understand the smallness of neutrino masses, is to assume neutrinos as Majorana particles, i.e.as their own antiparticles. Since this results in lepton number violation, it would at the same time be a potential mechanism to produce the matter antimatter asymmetry in the Universe. That is why it would be very attractive to prove the Majorana character of neutrinos experimentally.

The simplest but not simple method is to search for neutrinoless double beta decay. So far, no signal for neutrinoless double beta decay has been observed. Worldwide many experiments try with different detection methods: liquid noble gases, liquid scintillators, low temperature calorimetry or semiconductors. The GERDA experiment using Ge-semiconductor-detectors enriched in Ge-76, presently has the highest discovery potential, thanks to an extremely low rate of background signals and a very high energy resolution. The low background rate was achieved by using only materials very low in radioactivity, a combination of veto detectors and pulse shape discrimination to distinguish different event topologies.