The Gerda Experiment for the Search of Neutrinoless Double Beta Decay

The Gerda experiment, situated at Laboratori Nazionali del Gran Sasso is designed to search for the neutrinoless double $\beta$ decay. Bare high purity Ge-diodes enriched to 86 %in $^{76}Ge$ are directly immersed into liquid Ar. Phase I operated from November 2011 till May 2013 yielding an exposure of 21.6 kg·yr, with a mean background near the Q-value of2·$10^{−2}$ cts/(keV·kg·yr). A half-life of $1.84^{−0.10}_{+0.14}·10^{21}$ yr was recently published for the two-neutrino double $\beta$ decay. For Phase II, additional 20 kg of broad-energy Ge detectors will be installed to reach an exposure of 100 kg·yr with one order of magnitude less background, exploring half-lifes up to 1.5·$10^{26}$ yr. This will be achieved by liquid Ar instrumentation as an active veto, pulse shape analysis and a refined selection of radio-pure materials