Background Model for the Majorana Demonstrator

TL;DR

The paper discusses the development of a background model for the Majorana Demonstrator, aiming to achieve ultra-low background rates in germanium detectors for neutrino mass research.

Contribution

It presents a comprehensive background model combining material purity, analytical methods, and pulse shape analysis to reduce background noise in the experiment.

Findings

Background rate goals of 1 cnt/(ROI-t-y) are targeted.

Simulation and radioassay measurements are used to constrain background components.

Pulse shape analysis techniques effectively discriminate background events.

Abstract

The Majorana Collaboration is constructing a system containing 40 kg of HPGe detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale in the inverted-hierarchy region. To realize this, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials with analytical methods for background rejection, for example using powerful pulse shape analysis techniques profiting from the p-type point contact HPGe detectors technology. The effectiveness of these methods is assessed using simulations of the different background components whose purity levels are constrained from radioassay measurements.