Modeling of GERDA Phase II data

Abstract

The GERmanium Detector Array (GERDA) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double-beta ($0\nu \beta \beta$) decay of ${}^{76}$Ge. The technological challenge of GERDA is to operate in a "background-free" regime in the region of interest (ROI) after analysis cuts for the full 100kg$\cdot$yr target exposure of the experiment. A careful modeling and decomposition of the full-range energy spectrum is essential to predict the shape and composition of events in the ROI around $Q_{\beta \beta }$ for the $0\nu \beta \beta$ search, to extract a precise measurement of the half-life of the double-beta decay mode with neutrinos ($2\nu \beta \beta$) and in order to identify the location of residual impurities. The latter will permit future experiments to build strategies in order to further lower the background and achieve even better sensitivities. In this article the background decomposition prior to analysis cuts is presented for GERDA Phase II. The background model fit yields a flat spectrum in the ROI with a background index (BI) of $16.04_{-0.85}^{+0.78}\cdot 10^{-3}$cts/(kg$\cdot$keV$\cdot$yr) for the enriched BEGe data set and $14.68_{-0.52}^{+0.47}\cdot 10^{-3}$cts/(kg$\cdot$keV$\cdot$yr) for the enriched coaxial data set. These values are similar to the one of Gerda Phase I despite a much larger number of detectors and hence radioactive hardware components.

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• Final Results of GERDA on the Two-Neutrino Double-$\beta$ Decay Half-Life of ${}^{76}$Ge
• SAGE : A Monte Carlo Simulation Framework for Experiments with Germanium Detectors
• Liquid argon light collection and veto modeling in GERDA Phase II
• Optical properties of low background PEN structural components for the LEGEND-200 experiment
• A feasibility study of multi-electrode high-purity germanium detector for Ge-76 neutrinoless double beta decay searching
• Identification and simulation of surface alpha events on passivated surfaces of germanium detectors and the influence of metalisation
• Calibration of the GERDA experiment