Rare Event Searches with the DarkSide-50 Detector

Date

2018-12

Journal Title

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Abstract

While the Standard Model of particle physics has exhibited great success at describing much observed phenomena over the years, vast astrophysical evidence exists suggesting most of the matter in the universe is non-luminous and does not fit within the Standard Model.

There is consensus among cosmologists that most of this missing matter, referred to as dark matter, is composed of particles which are non-baryonic. Two of the leading candidates for this dark matter are Weakly Interacting Massive Particles (WIMPs) and axions. Dark matter has eluded laboratory detection, primarily due to the fact that is predicted to be very weakly interacting. Several experiments have been built to detect a nucleus recoiling from a WIMP colliding with a known atom.

Liquid noble gas detectors have demonstrated, that using novel background rejection techniques, rare events like WIMP recoils could be detected. DarkSide-50 (DS-50) is one such detector using liquid argon (LAr) technology. Over the years of operation in a background-free mode, DS-50 has not observed any WIMP events but has produced some competitive limits on WIMP-nucleon interaction cross sections for liquid argon detectors.

The low-background levels of DS-50 present the possibility to search for other hypothesized physics phenomena which are also predicted to rarely occur. Two of which are investigated in this dissertation.

One such search presented here is the hunt for neutrino-less double electron capture on an isotope of argon, 36Ar. The observation of such a decay would signify a substantial increase in our understanding of neutrinos, further providing a window of inspection into the observed matter anti-matter asymmetry in the universe.

Yet another search presented is the interaction of axions, coming from the Sun, with electrons in the LAr. An observation of such an interaction would validate the theory that solves the strong CP problem of the Standard Model, simultaneously providing evidence of the existence of a dark matter candidate.

Description

Keywords

Dark matter, WIMPs, Axions, Liquid argon, Liquids, Experimental Cosmology

Citation

Portions of this document appear in: P. Agnes et al. "CALIS - A CALibration Insertion System for the DarkSide-50 dark matter search experiment" Journal of Instrumentation 12 (12), T12004 Dec 2017. And in: P. Agnes et al. "The veto system of the DarkSide-50 experiment" Journal of Instrumentation 11(2016): P03016 Mar 2016. And in: P. Agnes et al. "Simulation of argon response and light detection in the DarkSide-50 dual phase TPC" Journal of Instrumentation 12 (10), P10015 Oct 2017. And in: P. Agnes et al. "Results from the first use of low radioactivity argon in a dark matter search" Physical Review D, 93(2016): 081101(R) Apr 2016. And in: P. Agnes et al. "DarkSide-50 532-day Dark Matter Search with Low-Radioactivity Argon" Phys. Rev. D 98, 102006 Nov 2018. And in: P. Agnes et al. "Low-mass Dark Matter Search with the DarkSide-50 Experiment" Phys. Rev. Lett. 121, 081307 Aug 2018. And in: P. Agnes et al. "Constraints on Sub-GeV Dark Matter-Electron Scattering from the DarkSide-50 Experiment" Phys. Rev. Lett. 121, 111303 Sep 2018. And in: P. Agnes et al. "Results from the first use of low radioactivity argon in a dark matter search" Physical Review D, 93(2016): 081101(R) Apr 2016. And in: C. E. Aalseth et al. "DarkSide-20k: A 20 Tonne Two-Phase LAr TPC for Direct Dark Matter Detection at LNGS" EPJ Plus 133:131 Mar 2018