Topologies of $^{76}$Ge double-beta decay events and calibration procedure biases

TL;DR

This paper investigates the topological differences between calibration and signal events in germanium detectors for neutrinoless double-beta decay, assessing biases in calibration procedures to improve future experimental accuracy.

Contribution

It characterizes the topological differences in event signals and evaluates calibration biases using $^{56}$Co and $^{228}$Th sources, enhancing calibration accuracy for $^{76}$Ge experiments.

Findings

Calibration samples differ subtly from true decay events.

Biases in calibration procedures can affect detection efficiency.

Results inform improved calibration methods for future experiments.

Abstract

The analysis of the time profile of electrical signals produced by energy depositions in germanium detectors allows discrimination of events with different topologies. This is especially relevant for experiments searching for the neutrinoless double beta decay of $^{76}$Ge to distinguish the sought-after signal from other background sources. The standard calibration procedures used to tune the selection criteria for double-beta decay events use a $^{228}$Th source, because it provides samples of signal-like events. These samples exhibit energy spatial distributions with subtle different topologies compared to neutrinoless double-beta decay events. In this work, we will characterize these topological differences and, with the support of a $^{56}$Co source, evaluate biases and precision of calibration techniques which use such event samples. Our results will be particularly relevant for future experiments in which a solid estimation of the efficiency is required.