Background modeling for the GERDA experiment

TL;DR

This paper presents a background modeling analysis for the GERDA experiment, crucial for detecting neutrinoless double beta decay, identifying key background sources and their contributions.

Contribution

It introduces a preliminary background model for GERDA, aiding in understanding and reducing background noise in the search for rare decay signals.

Findings

Main background sources identified include Bi-214, Th-228, K-42, Co-60, and Ra-226 decay chain isotopes.

The model estimates the background contribution in the signal region around Qbb.

Systematic uncertainties of the model are still under study.

Abstract

The neutrinoless double beta (0nubb) decay experiment GERDA at the LNGS of INFN has started physics data taking in November 2011. This paper presents an analysis aimed at understanding and modeling the observed background energy spectrum, which plays an essential role in searches for a rare signal like 0nubb decay. A very promising preliminary model has been obtained, with the systematic uncertainties still under study. Important information can be deduced from the model such as the expected background and its decomposition in the signal region. According to the model the main background contributions around Qbb come from Bi-214, Th-228, K-42, Co-60 and alpha emitting isotopes in the Ra-226 decay chain, with a fraction depending on the assumed source positions.