Neutrinoless Double Beta Decay with Germanium Detectors: 10$^{26}$ yr and Beyond

TL;DR

This paper reviews the use of germanium detectors in neutrinoless double beta decay searches, highlighting recent experimental achievements and introducing the LEGEND project aiming for unprecedented sensitivity to the decay half-life.

Contribution

It provides a comprehensive overview of the development and current status of Ge detector-based $0 uetaeta$ decay searches, and introduces the new LEGEND project for future exploration.

Findings

GERDA achieved an energy resolution of 2.53 keV at Q$_{etaeta}$

GERDA set a half-life limit of >1.8×10^{26} yr for $^{76}$Ge $0 uetaeta$ decay

LEGEND aims to reach a sensitivity of 10^{28} yr and beyond

Abstract

In the global landscape of neutrinoless double beta ($0\nu\beta\beta$) decay search, the use of semiconductor germanium detectors provides many advantages. The excellent energy resolution, the negligible intrinsic radioactive contamination, the possibility of enriching the crystals up to 88% in the $^{76}$Ge isotope as well as the high detection efficiency, are all key ingredients for highly sensitive $0\nu\beta\beta$ decay search. The MAJORANA and GERDA experiments successfully implemented the use of germanium (Ge) semiconductor detectors, reaching an energy resolution of $2.53 \pm 0.08$ keV at the Q$_{\beta\beta}$ and an unprecedented low background level of $5.2 \times 10^{-4}$ cts/(keV$\cdot$kg$\cdot$yr), respectively. In this paper, we will review the path of $0\nu\beta\beta$ decay search with Ge detectors from the original idea of E. Fiorini et al. in 1967, to the final recent results of the GERDA experiment setting a limit on the half-life of $^{76}$Ge $0\nu\beta\beta$ decay at $T_{1/2} > 1.8 \times 10^{26}$ yr (90\% C.L.). We will then present the LEGEND project designed to reach a sensitivity to the half-life up to $10^{28}$ yr and beyond, opening the way to the exploration of the normal ordering region.