This thesis is devoted to the study of the nature of Dark Matter (DM). To this end we investigate both its generation mechanisms and detection possibilities. We mainly focus on interesting simple models and follow closely experimental constraints, in order to reveal the features of DM as model-independently as possible.<p><p><p><p><p>Throughout the whole thesis, we consider the framework of standard cosmology, which is first introduced in Chapter.1 (and supplemented in Appendices). Background knowledges of DM physics from the cosmological and experimental aspects are given in Chapter.2 and Chapter.3, respectively. <p><p><p>Following the scenario that a hidden sector, including DM particles, might decouple from the Standard Model (SM) sector at a very early time of the Universe, we study how through a portal interaction such a hidden sector can be created by the SM sector to yield the proper relic density of dark matter. In Chapter.4 we discuss the case of a massless portal using the gauge kinetic mixing model. It turns out that there are four basic ways to achieve the observed DM relic density for both massless and massive mediator cases: freeze-in from SM sector, reannihilation determined by the balance of the two sectors, freeze-out with hidden or portal interactions. Various models with massive portals, especially $Z'$ and scalar portals, are then explored in Chapter.5. Provided that DM annihilation within the hidden sector is kinetically allowed, similar conclusions would appear. If there is no hidden annihilation for DM, only the first and last ways are allowed. Nevertheless, chemical thermalization in hidden sector can still influence the results significantly.<p><p>In Chapter.6, we explore the hypothesis that dark matter particles partially annihilate to photons via a new heavy charged particle which is also "gauged" under SU(3)_C. By applying this hypothesis to the claimed<p>Fermi-LAT 130 GeV gamma line, it is showed that the correct dark matter relic density could be naturally obtained from the gluon channel and how for such a class of models the cosmic antiproton, diffuse gamma-ray, direct detection and LHC constraints<p>are fully correlated. <p><p><p>In Chapter.8, concluding remarks and perspectives for future DM research are presented. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Lignes spectrales de rayons gammas provenants de la matière noire. <p>Approches indépendantes de modèles/ Gamma-Ray Lines from the Dark Side of Matter: Model-Independent Approaches<p><p> Cette thèse a pour thématique centrale la matière noire, et plus particulièrement un type de signal qu’elle pourrait émettre, à savoir des lignes spectrales de rayons gammas. La nature de la matière noire demeure mystérieuse, et ce que l’on sait de ses propriétés est exposé dans le premier chapitre. En particulier, la pertinence des lignes spectrales de rayons gammas dans l’étude de la matière noire est soulignée. Cette thèse est consacrée à l’étude des connexions possibles entre la phénoménologie de ce type de signal et d’autres manifestations, qu’il s’agisse de détection directe ou indirecte, ou bien de détection dans des collisionneurs tels que le LHC. Le but est d’établir la possibilité de discriminer différents modèles et/ou d’obtenir des contraintes indépendantes.<p>\ / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

<p align="justify">The success of Big Bang Nucleosynthesis (BBN) combined with the detailed analysis of the small imperfections of the Cosmic Microwave Background blackbody spectrum lead to the conclusion that most of the matter content of our universe is made of some non-baryonic material, the dark matter!</p><p><p><p align="justify">In this thesis, we review the compiling indications of dark matter and the so-called freeze-out mechanism which may settle the relic density of the species in the framework of the standard Big Bang model. We also examine principally two methods of detection of dark matter, direct and indirect detection searches.</p><p><p><p align="justify">Let us stress that the Standard Model on its own is unable to provide enough aspirants for the role of dark matter. As a consequence, one has to dig into the tremendous domain of physics "Beyond the Standard Model" in order to have a chance to elucidate the problem of the missing mass.</p><p><p><p align="justify">In this thesis in particular, we consider the Inert Doublet Model (IDM) which includes an additional Higgs doublet, enclosing two neutral scalars candidates for dark matter. We invoke the Standard freeze-out mechanism for the production of dark matter. We get then dark matter candidates in two rather separate mass ranges, one between 40 and 80 GeV, the other one between 400 GeV and 1 TeV. We also show that dark matter annihilation at the galactic center can be at the origin of a gamma-ray flux which can be probed by the future GLAST experiment.</p><p><p><p align="justify">We address a low reheating temperature scenario for the genesis of dark matter in a Left-Right symmetric extension of the Standard Model. The candidate for dark matter is a MeV right-handed neutrino and we show that a baryon-dark matter interaction at the galactic center can be the source of the low energy positrons responsible for the 511 keV gamma-ray excess observed by the INTEGRAL experiment in the galactic bulge region.</p><p><p><p align="justify">Finally, prompted by the possibility to explain the baryon and dark matter rather similar abundances by one single "Matter Genesis" mechanism, we study a non-thermal production mechanism for dark matter. The framework is also Left-Right symmetric and dark candidate is a ~3 GeV right handed neutrino.</p> <p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

L'expérience EDELWEISS a pour but de détecter des WIMPs, particules massives faiblement interactives, qui pourraient composer la matière noire de l'univers. Elle mesure l'énergie libérée lors de la collision élastique d'un WIMP sur un noyau de matière ordinaire. Du fait de sa très faible section efficace d'interaction, qui conduit à un taux d'évènement extrêment bas (<1evt/kg/an) et du fait du faible dépôt d'énergie (<100keV), le signal de recul nucléaire des WIMPs peut être imité par des neutrons de la radioactivité ambiante ou induits par des muons. Cette thèse est dédiée à l'étude du bruit de fond induit par les muons. Les performances du véto muon de l'expérience EDELWEISS-II sont présentées et la détection des muons er de leurs gerbes discutés. Les premières coïncidences entre le véto muon et les bolomètres ont été réalisées sur deux prises de données de 4 mois de 2007 et 2008 et conduisent à un résultat de 0.043+-0.015 coinc/kg/j pour une énergie de recul de ER<250 keV