Low Activity Background

In order to meet the sensitivity goal for the measurement of the neutrino mass, the signal of the 163Ho electron capture (EC) must dominate the background contributions. The pile up of these 163Ho decays within a single sensor sets a natural level for acceptable other background contributions of about 10-5 events per eV/day/detector in the endpoint region of the 163Ho spectrum. The goal of the background analysis is thus to identify potential background sources, investigate their strength and spectrum via Monte Carlo simulations and conceive and employ methods to reduce the contributions stronger than the background due to the unresolved pile-up of 163Ho EC events.

The resulting background contributions together with the unresolved pile-up events are then further analyzed to obtain an accurate model to describe their effect in the region of interest around the end-point.