Upgrade for Phase II of the GERDA Experiment

TL;DR

The GERDA experiment's Phase II upgrade successfully reduced background noise, enabling a more sensitive search for neutrinoless double beta decay of germanium-76, with significant improvements in detection capabilities.

Contribution

This paper details the modifications and improvements made to the GERDA experiment for Phase II, achieving background suppression and enhanced sensitivity.

Findings

Background suppressed by an order of magnitude

Experiment remains background-free up to its design exposure

Half-life sensitivity exceeds 10^26 years within 3 years

Abstract

The GERDA collaboration is performing a sensitive search for neutrinoless double beta decay of $^{76}$Ge at the INFN Laboratori Nazionali del Gran Sasso, Italy. The upgrade of the GERDA experiment from Phase I to Phase II has been concluded in December 2015. The first Phase II data release shows that the goal to suppress the background by one order of magnitude compared to Phase I has been achieved. GERDA is thus the first experiment that will remain background-free up to its design exposure (100 kg yr). It will reach thereby a half-life sensitivity of more than 10$^{26}$ yr within 3 years of data collection. This paper describes in detail the modifications and improvements of the experimental setup for Phase II and discusses the performance of individual detector components.