Liquid argon light collection and veto modeling in GERDA Phase II

The ability to detect liquid argon scintillation light from within a densely packed high-purity germanium detector array allowed the GERDA experiment to reach an exceptionally low background rate in the search for neutrinoless double beta decay of Ge-76. Proper modeling of the light propagation throughout the experimental setup, from any origin in the liquid argon volume to its eventual detection by the novel light read-out system, provides insight into the rejection capability and is a necessary ingredient to obtain robust background predictions. In this paper, we present a model of the GERDA liquid argon veto, as obtained by Monte Carlo simulations and constrained by calibration data, and highlight its application for background decomposition.

Automated summary

The GERDA experiment achieved an exceptionally low background rate in the search for neutrinoless double beta decay of Ge-76 by detecting liquid argon scintillation light from within a densely packed high-purity germanium detector array. Modeling the light propagation throughout the experimental setup and its detection by the novel light read-out system is crucial for rejection capability and robust background predictions. This paper presents a model of the GERDA liquid argon veto obtained through Monte Carlo simulations and calibration data, highlighting its application for background decomposition.