Impact of extreme ultraviolet radiation on the scintillation of pure and xenon-doped liquid argon

TL;DR

This study investigates how extreme ultraviolet radiation influences scintillation in pure and xenon-doped liquid argon, revealing a long-lived EUV component that enhances light yield and impacts detector performance.

Contribution

It provides the first evidence of a long-lived EUV emission component in LAr scintillation and develops a comprehensive model including collisional and radiative processes.

Findings

EUV component contributes to increased light yield.

Xenon doping enhances the EUV emission.

Implications for improving noble liquid detector sensitivity.

Abstract

The Xenon-Argon Technology (X-ArT) collaboration presents a study on the dynamics of pure and xenon-doped liquid argon (LAr) scintillation. Using two types of silicon photomultipliers sensitive to different wavelength ranges, we provide evidence in favor of a contribution from long-lived (>10 $\mu$s) extreme ultraviolet (EUV) lines emitted from argon atomic states, which enhances the light yield. This component is present in both pure and xenon-doped LAr, becoming more pronounced at higher xenon concentrations, where it complements the traditional collisional energy transfer process. To explain this mechanism, we develop a comprehensive model of the Xe-doped LAr scintillation process that integrates both collisional and radiative contributions. Additionally, we investigate how xenon doping affects LAr scintillation light yield and pulse shape discrimination. Finally, we hypothesize that the EUV component may explain the emission of spurious electrons, a known challenge in light dark matter searches using noble liquids. By characterizing the scintillation dynamics in Xe-doped LAr, identifying the long-lived EUV component, and exploring the potential origin of spurious electrons, this work lays the groundwork for optimizing detector performance and advancing the design and sensitivity of future noble liquid particle detectors.