Virtual depth by active background suppression: Revisiting the cosmic muon induced background of GERDA Phase II

Abstract

In-situ production of long-lived isotopes by cosmic muon interactions may generate a non-negligible background for deep underground rare event searches. Previous Monte Carlo studies for the GERDA experiment at LNGS identified the delayed decays of ${}^{77}$Ge and its metastable state ${}^{77m}$Ge as dominant cosmogenic background in the search for neutrinoless double beta decay of ${}^{76}$Ge. This might limit the sensitivity of next generation experiments aiming for increased ${}^{76}$Ge mass at background-free conditions and thereby define a minimum depth requirement. A re-evaluation of the ${}^{77(m)}$Ge background for the GERDA experiment has been carried out by a set of Monte Carlo simulations. The obtained ${}^{77(m)}$Ge production rate is (0.21$\pm$0.01) nuclei/(kg$\cdot$yr). After application of state-of-the-art active background suppression techniques and simple delayed coincidence cuts this corresponds to a background contribution of (2.7$\pm$0.3)$\cdot 10^{-6}$ cts/(keV$\cdot$kg$\cdot$yr). The suppression achieved by this strategy equals an effective muon flux reduction of more than one order of magnitude. This virtual depth increase opens the way for next generation rare event searches.

9 pages, 5 figures

References in corpus (16)

• Improved limit on neutrinoless double beta decay of ${}^{76}$Ge from GERDA Phase II
• Background free search for neutrinoless double beta decay with GERDA Phase II
• The GERDA experiment for the search of 0νββ decay in ^{76}Ge
• The Large Enriched Germanium Experiment for Neutrinoless Double Beta Decay (LEGEND)
• Search for Zero-Neutrino Double Beta Decay in 76Ge with the Majorana Demonstrator
• \textsc{MaGe} - a {\sc Geant4}-based Monte Carlo Application Framework for Low-background Germanium Experiments
• Muon simulation codes MUSIC and MUSUN for underground physics
• Upgrade for Phase II of the GERDA Experiment
• Neutron- and muon-induced background in underground physics experiments
• Cosmogenic activation of materials
• Mitigation of ${}^{42}$Ar/${}^{42}$K background for the GERDA Phase II experiment
• The Performance of the Muon Veto of the GERDA Experiment
• Cosmogenic Activation of Germanium Used for Tonne-Scale Rare Event Search Experiments
• The Muon-Induced Neutron Indirect Detection EXperiment, MINIDEX
• Direct measurement of neutrons induced in lead by cosmic muons at a shallow underground site
• Calculations of Nuclear Astrophysics and Californium Fission Neutron Spectrum Averaged Cross Section Uncertainties using ENDF/B-VII.1, JEFF-3.1.2, JENDL-4.0 and Low-Fidelity Covariances

Cited by in corpus (5)

• Modeling of GERDA Phase II data
• Cosmogenic activation in double beta decay experiments
• Signatures of muonic activation in the Majorana Demonstrator
• Experimental study of 13C(α,n)16O reactions in the Majorana Demonstrator calibration data
• Calibration sources for the LEGEND-200 experiment