Simulation of argon response and light detection in the DarkSide-50 dual phase TPC

TL;DR

This paper presents G4DS, a detailed Geant4-based simulation package for the DarkSide-50 liquid argon detector, crucial for understanding detector response, background rejection, and argon contamination in WIMP searches.

Contribution

The paper introduces G4DS, a comprehensive Monte Carlo simulation tailored for DarkSide-50, including a novel liquid argon response model called PARIS, enhancing detector response accuracy.

Findings

Achieved electron recoil background rejection of ~10^7.

Measured residual 39Ar contamination in underground argon.

Validated simulation accuracy against experimental data.

Abstract

A Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ~10^7, using the pulse shape discrimination technique, and the measurement of the residual 39Ar contamination in underground argon, ~3 orders of magnitude lower with respect to atmospheric argon. These results rely on the accurate simulation of the detector response to the liquid argon scintillation, its ionization, and electron-ion recombination processes. This work provides a complete overview of the DarkSide Monte Carlo and of its performance, with a particular focus on PARIS, the custom-made liquid argon response model.