Neutrino physics has been going through rapid developments since the particle was first proposed by Pauli. The observation of neutrino oscillations has prompted an investigation of the issue of neutrino mass, with the "seesaw" mechanism garnering theoretical support. The HUNTER (Heavy Unseen Neutrinos from the Total Energy-momentum Reconstruction) experiment brings together AMO, nuclear physics and high energy physics researchers from Temple University, Houston University, UCLA and Princeton University to develop an apparatus capable of probing the keV-mass range of sterile neutrinos with high precision. The HUNTER detector makes use of the well-established COLTRIMS techniques for the collection of all the decay products of a neutrino-producing decay, and the reconstruction of their initial momenta and energies. Energy and momentum conservation allow then for the reconstruction of the missing neutrino mass.Electrons produced in the decay are guided towards their detector by an optimized set of electrodes paired to a magnetic field to confine their trajectories into spirals. A magnetic shield protects the electron from external stray fields that could alter their trajectories. A thorough study on the main source of background, namely the source scattering of ions, was conducted. As an additional topic, the feasibility of a directional-sensitive dark matter search experiment has been studied. Simple models of galactic dark matter distribution suggest that the motion of the Earth in space might introduce a directional anisotropy in the WIMPs momentum distribution at the Earth. The shape of a WIMP-like recoil in a target material could be be used to extract directional information for the incident WIMP, and thus confirm the anisotropy. The peculiar microphysics of liquid Argon requires thermalization of ionization electrons for a signal to form. To determine if directional information can be extracted, one needs to understand the energy spectrum of the electrons emitted in recoil event. Then, one needs a model to determine the time scale of the thermalization, and the distance to which the electrons travel. / Physics

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De nombreuses observations astrophysiques et cosmologiques tendent à prouver que la matière ordinaire (dite baryonique) ne constituerait qu'environ 5 % du contenu énergétique de l'Univers. Les principales composantes de celui-ci seraient l'énergie noire (à 70 %) ainsi que la matière noire (à 25 %). Cette dernière serait invisible et seuls ses effets gravitationnels traduiraient sa présence dans l'Univers. Plusieurs particules, regroupées sous le terme générique de WIMP (Weakly Interacting Massive Particles), pourraient correspondre à cette théorie et sont activement recherchées. Plusieurs dispositifs expérimentaux ont été développés dans ce but et s'appuyent sur les stratégies suivantes : la production de ces particules au sein de collisionneurs, l'observation de particules produites via l'annihilation de WIMP ou encore la détection directe de ces particules via leur interaction avec le noyau des atomes constitutifs d'un détecteur. C'est sur cette dernière méthode que s'appuie l'expérience EDELWEISS. Il s'agit d'une expérience de détection directe de matière noire dédiée à la recherche de WIMP de masse comprise entre 1 GeV et 1 TeV. Son but premier est de détecter les reculs nucléaires induits par la diffusion élastique de particule de matière noire dans les détecteurs. Les taux d'événements attendus < 10 /(kg.an) étant de plusieurs ordres de grandeur inférieurs à ceux induits par la radioactivité ambiante, une double mesure de l'ionisation et de la chaleur est employée pour discriminer les reculs électroniques induits par les bruits de fonds β et γ des reculs nucléaires induits par les WIMPs. De plus, l'expérience a été placée en site souterrain pour se prémunir des rayonnements cosmiques, induisant des événements dans les détecteurs. Ceux utilisés par l'expérience sont des bolomètres en germanium, appelés FID, refroidis à des températures cryogéniques (18 mK) et opérant à bas champ (1 V/cm). Depuis 2015, la nouvelle stratégie de l'expérience consiste à se focaliser sur les WIMPs de masse inférieure à 10 GeV, zone de recherche privilégiée pour les expériences utilisant des détecteurs cryogéniques. Le fonctionnement de l'expérience a donc été amélioré afin d'atteindre cet objectif.Le but de cette thèse consiste à analyser les campagnes de données de l'expérience, effectuées en 2015 et 2016. Celles-ci utilisaient les détecteurs FID soumis à un champ électrique plus important que précédemment afin d'améliorer leur sensibilité. La limite extraite à partir de ces données s'appuie sur la statistique de Poisson et a permis de mettre en évidence que le bruit de fond dominant de l'expérience à basse énergie impacte grandement les résultats. C'est pourquoi une étude de ces événements, appelés heat-only, a été réalisée. Ceux-ci se caractérisent par une élévation de chaleur vue par les senseurs thermiques sans que les électrodes du détecteur ne mesurent d'ionisation en son sein. Une étude de ce bruit de fond a été réalisée et a permis de mettre en évidence la possibilité de modéliser ces événements. Suite à ces résultats, une analyse par maximum de vraisemblance a été construite. Cette méthode d'analyse permet de soustraire de manière statistique les bruits de fond de l'expérience grâce à leurs spectres en énergie différents de ceux attendus pour un signal de matière noire. De cette façon, une limite sur la section efficace des WIMP a été calculée en utilisant pour la première fois des détecteurs FID soumis à des champs électriques supérieurs aux valeurs utilisées jusqu'à présent / Many astrophysical and cosmological observations lead to postulate the existence of an unknown matter, called dark matter. Ordinary matter can explain only 5 % of the energy content of the Universe : the main components would be the dark energy (70 %) and dark matter (25 %). This latter is invisible and manifest itself only via its gravitational effects. Several particles, grouped under the generic term of WIMP (Weakly Interacting Massive Particles), could correspond to this theory and are actively searched. Many experiments have been developed for this purpose and are based on three strategies: the production of these particles with colliders, the observation of the particles produced by their annihilation in astrophysical objects or the direct detection of these particles via their interaction with the nucleus of the atoms constituent of a detector. It is on this last method that the EDELWEISS experiment is based. It is a dark matter direct detection experiment dedicated to the search for WIMP with masses between 1 GeV and 1 TeV. Its primary purpose is to detect nuclear recoils induced by elastic scattering of dark matter particles in detectors. Since the expected event rates < 10 /(kg.year) are several orders of magnitude lower than those induced by ambient radioactivity, a double measurement of ionization and heat is used to discriminate electron-induced recoils arising from β and γ interactions from WIMP-induced nuclear recoils. In addition, the experiment was placed underground to guard against cosmic radiation, inducing events in the detectors. These are germanium bolometers, called FID, cooled to cryogenic temperatures (18 mK) and operating at low field (1 V/cm). Since 2015, the new strategy of the experiment consists of focusing on WIMPs with mass below 10 GeV, an interessant research area where experiments using cryogenic detectors can exploit their ability to operate with experimental thresholds well below 1 keV. The operation of the experiment has been improved to achieve this goal. The aim of this thesis is to analyze the data set recorded by EDELWEISS in 2015 and 2016. These used the FID detectors subjected to a greater electric field than previously to improve their sensitivity. It is expected that the limit on the spin-independent WIMP-nucleon crosssection extracted from these data will be greatly impacted by a dominant background, called heat-only events. That is why they are studied in detail in this work. They are characterized by a rise in heat seen by thermal sensors without any ionization signal on the collecting electrodes. This study resulted in to highlight a model for these events that can be used in the WIMP search analyses. Following these results, a maximum likelihood analysis was constructed. This method of analysis makes it possible to statistically subtract the background noise from the experiment by exploiting the difference between the energy spectra of signal and backgrounds. In this way, limits on the spin-independent WIMP-nucleon cross-section are obtained. They will be compared to the results of other experiments

Many astronomical observations, including rotational curve measurements of stars and the analysis of the cosmic microwave background, suggest the existence of an invisible matter density content in the Universe, commonly called Dark Matter (DM). Possibly, DM could be of particle nature, where Weakly Interacting Massive Particles (WIMPs) could be a viable DM candidate. The cubic-kilometer sized IceCube neutrino observatory located at the Earth’s South Pole can search indirectly for the existence of DM by detecting neutrino signals from WIMP self-annihilation in the Galactic center (GC) and the Galactic halo (GH). Two main physics analyses were developed and conducted to search indirectly for WIMP self-annihilation in the Milky Way’s GC and GH. Signal hypotheses for different WIMP annihilation channels, WIMP masses and DM halo profiles were tested. The results of both analyses were compatible with the background-only hypothesis for all tested signal hypotheses. Thus, upper limits at the 90% confidence level (C.L.) on the thermally averaged DM self-annihilation cross-section, &lt;σΑv&gt;, were set. Dedicated atmospheric muon veto techniques have been developed for the GC search making such an IceCube analysis possible for the first time. The GC analysis utilized data from 319.7 days of live-time of the IceCube detector running in its 79-string configuration during 2010 and 2011, whereas the GH analysis utilized pre-existing data samples developed for point-like neutrino sources with a live-time of 1701.9 days between 2008 and 2013. The most stringent upper limits on &lt;σΑv&gt; were obtained for WIMP annihilation directly into a pair of neutrinos assuming a Navarro-Frenk-White (NFW) DM halo profile. Conducting the GC and GH analyses for this annihilation channel an upper limit on &lt;σΑv&gt; as low as 4.0 · 10-24 cm3 s-1 and 4.5 · 10-24 cm3 s-1 is set for a 65 GeV and 500 GeV massive WIMP, respectively. These galactic indirect neutrino searches for DM are complementary to the indirect gamma-ray DM searches usually performed on extra-galactic targets like spheroidal dwarf galaxies. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.</p>

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New constraints on the scattering cross sections of the Kaluza Klein photon as a darkmatter candidate, its annihilation rate in the Sun and the resulting muon flux on Earth are derived.For this purpose, data collected in the IceCube Neutrino Observatory during 532 days of exposurein the austral winters between 2011 and 2014 have been analyzed with Poisson confidence intervals (J. Conrad et al., 2003) and compared to the simulated prediction achieved with the WimpSimsoftware (J. Edsjö et al., 2003). The results do not allow for any detection claim, but they improveby one order of magnitude the constraints formerly presented in R. Abbasi et al. (2010). Despitethe recent results from LHC experiment which discard lower masses for the Kaluza Klein photon (N. Deutschmann et al., 2017), the new constraints are still relevant for masses above 1500 GeV.

<p>A relic density of <i>Weakly Interacting Massive Particles</i> (WIMPs) remaining from the Big Bang constitutes a promising solution to the <i>Dark Matter</i> problem. It is possible for such WIMPs to be trapped by and accumulate in gravitational potentials of massive dense objects such as the Sun. A perfect WIMP candidate appears in certain <i>supersymmetric</i> extensions to the <i>Standard Model</i> of particle physics, where the lightest supersymmetric particle is a <i>neutralino</i> which can be stable, massive and weakly interacting. The neutralinos may annihilate pair-wise and in these interactions neutrinos with energies ranging up to the neutralino mass can be indirectly produced. Hence, a possible population of dark matter neutralinos trapped in the Sun can give rise to an observable neutrino flux.</p><p>The Antarctic Muon And Neutrino Detector Array, AMANDA, is a neutrino telescope that detects Cherenkov light emitted by charged particles created in neutrino interactions in the South Pole glacial ice sheet using an array of light detectors frozen into the deep ice. In this work data taken with the AMANDA-II detector during 2003 are analyzed to measure or put upper bounds on the flux of such neutrinos from the Sun. In the analysis detailed signal and background simulations are compared to measurements. Background rejection filters optimized for various neutralino models have been constructed. No excess above the background expected from neutrinos and muons created in cosmic ray interactions in the atmosphere was found. Instead 90% confidence upper limits have been set on the neutralino annihilation rate in the Sun and the muon flux induced by neutralino signal neutrinos. </p>

A search for weakly interacting massive particles (WIMPs) annihilating in the Sun was performed with the IceCube and AMANDA neutrino telescopes, using data from 2008 corresponding to 149 days of livetime. Assuming that particles in the dark matter halo scatter and accumulate in the centre of the Sun, Majorana WIMPs may pair-wise annihilate and give rise to a neutrino signal detectable in an experiment at Earth. No excess of muon-neutrinos from the Sun was observed, and limits on the νμ-flux were set for masses between 50 GeV and 5 TeV considering WIMPs annihilating into b‾b and W+W-. Separate limits were also calculated for the case of the lightest Kaluza-Klein particle. The flux limits were converted to limits on the spin-dependent and spin-independent WIMP-proton cross sections, σSD and σSI. The search was combined using a joint likelihood method with AMANDA and IceCube data from 2001-2007, yielding the 90% CL upper limits Φμ &lt; 103 km-2y-1 for a WIMP mass of 1000 GeV and σSD &lt; 1.28×10-4 pb for 250 GeV, both for the W+W- spectrum. / IceCube