First results from GERDA Phase II

Abstract

Gerda is designed for a background-free search of 76Ge neutrinoless double-β decay, using bare Ge detectors in liquid Ar. The experiment was upgraded after the successful completion of Phase I to double the target mass and further reduce the background. Newly-designed Ge detectors were installed along with LAr scintillation sensors. Phase II of data-taking started in Dec 2015 with approximately 36 kg of Ge detectors and is currently ongoing. The first results based on 10.8 kg• yr of exposure are presented. The background goal of 10-3 cts/(keV• kg• yr) is achieved and a search for neutrinoless double-β decay is performed by combining Phase I and II data. No signal is found and a new limit is set at yr (90% C.L.).