Analysis of the first underground run and background studies of the Argon Dark Matter

Résumé

Dark Matter is a collisionless and non-luminous kind of matter, whose existence is inferred through its gravitational e ects at the galactic, cluster and large scales in the Universe. From the analysis of the PLANCK latest data, Dark Matter accounts for the 26.6% of the composition of the energy density of the Universe, while ordinary matter only represents 4.9% [1]. Revealing the nature of Dark Matter has become one of the most challenging problems in modern physics. A possible explanation comes from particle physics in the form of Weakly Interacting Massive Particles (WIMPs), a particularly interesting class of new particle that can naturally account for the measured abundance of Dark Matter. WIMPs would be produced thermally in the early Universe and, since they interact only weakly, their annihilation rate would become insigni cant as the Universe expands, thus freezing out with a relic abundance. Supersymmetry, an extension of the Standard Model of particle physics, foresees interesting possible WIMP candidates in the form of the Lightest Supersymmetric Particle (LSP), which is neutral, stable and massive. A great experimental e ort has been undertaken in the last years to detect Dark Matter in underground and space-based detectors or produce it in accelerators. This Thesis is focused on the analysis of the rst underground run and background studies of the Argon Dark Matter (ArDM) experiment, which aims to detect WIMPs via the nuclear recoils produced by their elastic scattering o argon nuclei. The detector is a ton-scale double-phase (liquid-gas) TPC, which is currently installed at the Canfranc Underground Laboratory (LSC) under the Pyrenees in Spain and it is the rst ton-scale argon detector for Dark Matter to take data underground.