# Analysis of backgrounds for the ANAIS-112 dark matter experiment

## TL;DR

The paper presents detailed background models for the ANAIS-112 dark matter detector, crucial for testing DAMA/LIBRA's annual modulation signal, demonstrating the detector's sensitivity and background characterization efforts.

## Contribution

It provides comprehensive background models for all nine ANAIS-112 detectors, enabling sensitive dark matter search and validation of previous modulation signals.

## Key findings

- Background level in 1-6 keVee is 3.58+-0.02 keV-1 kg-1 day-1
- Dominant background sources include 210Pb, 40K, 22Na, and 3H
- ANAIS-112 can explore DAMA/LIBRA's modulation signal at three sigma in 5 years.

## Abstract

The ANAIS (Annual modulation with NaI(Tl) Scintillators) experiment aims at the confirmation or refutation of theDAMA/LIBRA positive annual modulation signal in the low energy detection rate, using the same target and technique, at the Canfranc Underground Laboratory (LSC) in Spain. ANAIS-112, consisting of nine 12.5 kg NaI(Tl) modules produced by Alpha Spectra Inc. in a 3x3matrix configuration, is taking data smoothly in "dark matter search" mode since August, 2017, after a commissioning phase and operation of the first detectors during the last years in various setups. A large effort has been carried out withinANAIS to characterize the background of sodium iodide detectors, before unblinding the data and performing the first annual modulation analysis. Here, the background models developed for all the nine ANAIS-112 detectors are presented. Measured spectra from threshold to high energy in different conditions are well described by the models based on quantified activities independently estimated following several approaches. In the region from 1 to 6 keVee the measured, efficiency corrected background level is 3.58+-0.02 keV-1 kg-1 day-1; NaI crystal bulk contamination is the dominant background source being 210Pb, 40K, 22Na and 3H contributions the most relevant ones. This background level, added to the achieved 1 keVee analysis threshold (thanks to the outstanding light collection and robust filtering procedures developed), allow ANAIS-112 to be sensitive to the modulation amplitude measured by DAMA/LIBRA, and able to explore at three sigma level in 5 years the WIMP parameter region singled out by this experiment.