PNNL

Abstract

The background index is an important quantity which is used in projecting and calculating the half-life sensitivity of neutrinoless double-beta decay (0?ßß) experiments. A novel analysis framework is presented to calculate the background index using the specific activities, masses and simulated efficiencies of an experiment’s components as distributions. This Bayesian framework includes a unified approach to combine specific activities from assay. Monte Carlo uncertainty propagation is used to build a background index distribution from the specific activity, mass and efficiency distributions. This analysis method is applied to the Majorana Demonstrator, which deployed arrays of high-purity Ge detectors enriched in 76Ge to search for 0?ßß. The framework projects a mean background index of [1.16 ± 0.04] × 10-3 cts/(keV kg yr) for the Demonstrator.