# Search for dark matter with a 231-day exposure of liquid argon using DEAP-3600 at SNOLAB

## TL;DR

This paper reports on a dark matter search using the DEAP-3600 liquid argon detector at SNOLAB, setting new limits on WIMP-nucleon interactions based on 231 days of data with advanced background suppression and analysis techniques.

## Contribution

The study introduces improved pulse-shape discrimination, Bayesian photoelectron counting, and dual position reconstruction algorithms in a large liquid argon detector for dark matter detection.

## Key findings

- No candidate events observed in the WIMP search region.
- Sets the leading limit on WIMP-nucleon cross section for 100 GeV/c² WIMPs.
- Demonstrates the best pulse-shape discrimination in liquid argon at threshold.

## Abstract

DEAP-3600 is a single-phase liquid argon (LAr) direct-detection dark matter experiment, operating 2 km underground at SNOLAB (Sudbury, Canada). The detector consists of 3279 kg of LAr contained in a spherical acrylic vessel. This paper reports on the analysis of a 758 tonne\cdot day exposure taken over a period of 231 live-days during the first year of operation. No candidate signal events are observed in the WIMP-search region of interest, which results in the leading limit on the WIMP-nucleon spin-independent cross section on a LAr target of $3.9\times10^{-45}$ cm$^{2}$ ($1.5\times10^{-44}$ cm$^{2}$) for a 100 GeV/c$^{2}$ (1 TeV/c$^{2}$) WIMP mass at 90\% C. L. In addition to a detailed background model, this analysis demonstrates the best pulse-shape discrimination in LAr at threshold, employs a Bayesian photoelectron-counting technique to improve the energy resolution and discrimination efficiency, and utilizes two position reconstruction algorithms based on PMT charge and photon arrival times.