Interpretable Boosted Decision Tree Analysis for the Majorana Demonstrator

TL;DR

This paper introduces the first interpretable machine learning analysis of Majorana germanium detector data, using gradient boosted decision trees to improve background rejection and provide insights to traditional analysis methods.

Contribution

It presents a novel, interpretable machine learning approach for germanium detector data, enhancing background rejection and informing traditional analysis techniques.

Findings

Machine learning improves background rejection in germanium detectors.

Interpretability reveals key features influencing classification.

Method is compatible with next-generation experiments like LEGEND.

Abstract

The Majorana Demonstrator is a leading experiment searching for neutrinoless double-beta decay with high purity germanium detectors (HPGe). Machine learning provides a new way to maximize the amount of information provided by these detectors, but the data-driven nature makes it less interpretable compared to traditional analysis. An interpretability study reveals the machine's decision-making logic, allowing us to learn from the machine to feedback to the traditional analysis. In this work, we have presented the first machine learning analysis of the data from the Majorana Demonstrator; this is also the first interpretable machine learning analysis of any germanium detector experiment. Two gradient boosted decision tree models are trained to learn from the data, and a game-theory-based model interpretability study is conducted to understand the origin of the classification power. By learning from data, this analysis recognizes the correlations among reconstruction parameters to further enhance the background rejection performance. By learning from the machine, this analysis reveals the importance of new background categories to reciprocally benefit the standard Majorana analysis. This model is highly compatible with next-generation germanium detector experiments like LEGEND since it can be simultaneously trained on a large number of detectors.