The background in the neutrinoless double beta decay experiment GERDA

Abstract

The GERmanium Detector Array (GERDA) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double beta decay of 76Ge. The signature of the signal is a monoenergetic peak at 2039 keV, the Q-value of the decay, Q_bb. To avoid bias in the signal search, the present analysis does not consider all those events, that fall in a 40 keV wide region centered around Q_bb. The main parameters needed for the neutrinoless double beta decay analysis are described. A background model was developed to describe the observed energy spectrum. The model contains several contributions, that are expected on the basis of material screening or that are established by the observation of characteristic structures in the energy spectrum. The model predicts a flat energy spectrum for the blinding window around Q_bb with a background index ranging from 17.6 to 23.8*10^{-3} counts/(keV kg yr). A part of the data not considered before has been used to test if the predictions of the background model are consistent. The observed number of events in this energy region is consistent with the background model. The background at Q-bb is dominated by close sources, mainly due to 42K, 214Bi, 228Th, 60Co and alpha emitting isotopes from the 226Ra decay chain. The individual fractions depend on the assumed locations of the contaminants. It is shown, that after removal of the known gamma peaks, the energy spectrum can be fitted in an energy range of 200 kev around Q_bb with a constant background. This gives a background index consistent with the full model and uncertainties of the same size.

References in corpus (6)

• The GERDA experiment for the search of 0νββ decay in ^{76}Ge
• \textsc{MaGe} - a {\sc Geant4}-based Monte Carlo Application Framework for Low-background Germanium Experiments
• Measurement of the specific activity of Ar-39 in natural argon
• Status and prospects of searches for neutrinoless double beta decay
• Neutron Inelastic Scattering Processes as Background for Double-Beta Decay Experiments
• Background modeling for the GERDA experiment

Cited by in corpus (30)

• DarkSide-20k: A 20 Tonne Two-Phase LAr TPC for Direct Dark Matter Detection at LNGS
• Background free search for neutrinoless double beta decay with GERDA Phase II
• Results on $\beta \beta$ decay with emission of two neutrinos or Majorons in ${}^{76}$Ge from GERDA Phase I
• Production, characterization and operation of ${}^{76}$Ge enriched BEGe detectors in GERDA
• Analysis of backgrounds for the ANAIS-112 dark matter experiment
• Developing the MeV potential of DUNE: Detailed considerations of muon-induced spallation and other backgrounds
• Site-selection criteria for the Einstein Telescope
• Assessment of backgrounds of the ANAIS experiment for dark matter direct detection
• Deep learning based pulse shape discrimination for germanium detectors
• Electromagnetic Backgrounds and Potassium-42 Activity in the DEAP-3600 Dark Matter Detector
• Identification of Radiopure Titanium for the LZ Dark Matter Experiment and Future Rare Event Searches
• Cosmogenic activation of materials
• Pulse shape discrimination performance of Inverted Coaxial Ge detectors
• Background assessment for the TREX Dark Matter experiment
• Mitigation of ${}^{42}$Ar/${}^{42}$K background for the GERDA Phase II experiment
• Cosmogenic production of ${}^{39}$Ar and ${}^{37}$Ar in argon
• $2\nu \beta \beta$ decay of ${}^{76}$Ge into excited states with GERDA Phase I
• Cosmogenic activation in double beta decay experiments
• Limits on uranium and thorium bulk content in GERDA Phase I detectors
• Cosmic-ray induced background intercomparison with actively shielded HPGe detectors at underground locations
• On concentration of ${}^{42}$Ar in the Earth's atmosphere
• Status of double beta decay experiments using isotopes other than Xe-136
• The GALATEA Test-Facility for High Purity Germanium Detectors
• Spectral shapes of forbidden argon beta decays as background component for rare-event searches
• Background Rejection of n${}^{+}$ Surface Events in GERDA Phase II
• Measurement of the ion fraction and mobility of ${}^{218}$Po produced in ${}^{222}$Rn decays in liquid argon
• Mass spectrometric analyses of high performance polymers to assess radiopurity as ultra low background materials for rare event physics detectors
• Background Evaluation for the Neutron Sources in the Daya Bay Experiment
• Study of cosmogenic activation in ${}^{76}$Ge enriched germanium detectors during fabrication and transportation above ground
• AlphaCAMM, a Micromegas-based camera for high-sensitivity screening of alpha surface contamination