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

Le LAT est l'instrument principal du satellite Fermi et permet d'étudier le ciel en rayons gamma de 20 MeV à plus de 300 GeV. Sa sensibilité accrue a permis l'augmentation du nombre de sources détectées dans le domaine des hautes énergies. Une partie importante de celles-ci n'a pas de contrepartie connue et une étude multi-longueur d'onde est nécessaire afin de comprendre l'origine du signal observé. Dans un premier temps, cette thèse présente l'étude morphologique et spectrale détaillée de la source non-identifiée HESS J1745--303, qui a été découverte dans le domaine gamma par l'expérience H.E.S.S. en 2006 puis analysée spécifiquement dans un article de 2008, à l'aide des données du LAT. Deux sources ponctuelles situées à une localisation proche de HESS J1745-303 sont présentes dans le catalogue à deux ans de données de Fermi (2FGL) mais une analyse dédiée de cette région est néanmoins nécessaire vu sa complexité. Elle est en effet localisée à ~1° du Centre Galactique et à moins de 0.5° du pulsar de la Souris, les deux sources les plus brillantes en gamma dans cette région.Les différents processus d'émission de photons sont présentés dans un second temps. Leurs simulations permettent d'effectuer une étude approfondie de l'origine de l'émission détectée aux hautes et très hautes énergies par le LAT et par H.E.S.S. L'émission de cette source reste en effet encore énigmatique de nos jours et une étude multi-longueur d'onde est effectuée afin de contraindre les modèles d'émission. / The LAT is the main instrument onboard the Fermi space telescope and performs unprecedented observations of the gamma-ray sky between 20 MeV and more than 300 GeV. The number of gamma-ray sources detected has grown thanks to its high sensibility. A large part of these sources has no known counterpart and a multi-wavelength study is needed in order to understand the origin of the observed signal.This thesis presents a morphological and spectral detailed study of the unidentified source HESS J1745--303, which was discovered in gamma-rays in 2006 with the H.E.S.S. experiment, using the Fermi-LAT data. Two point-like sources, located near HESS J1745--303, are included in the Fermi Large Area Telescope Second Source Catalog (2FGL) but, due to the complexity of this region, a dedicated study of the LAT data is however needed. Indeed, its location is ~1° away from the Galactic Center source and less than 0.5° from the Mouse pulsar, the two brightest gamma-ray sources in this region.The astrophysical emission processes are then detailed. We develop an extensive code which allowed us to study the origin of the HE (High Energy) and VHE (Very-High Energy) gamma-ray emissions detected by the LAT and H.E.S.S. The emission of this source is indeed still enigmatic and we perform a mutli-wavelength study to try to constrain the emission modeling.

Orientador: Saulo Henrique Pereira / Resumo: Neste trabalho é construída a evolução completa do Universo impulsionada pelo espinor escuro com dimensão de massa um, chamado MDO. O modelo começa pela inflação cósmica, passando pela era dominada pela matéria escura, terminando com a recente expansão acelerada. Além disso, é feita uma primeira aproximação à teoria de perturbação escalar. Foi mostrado que a dinâmica do campo fermiônico MDO, respeitando um potencial com quebra de simetria, pode reproduzir todas as fases do Universo de uma maneira natural e elegante. As equações dinâmicas em geral e as condições de Slow-Roll, no limite H mp, também são apresentadas para o referido sistema. A análise numérica para o número de e-folds durante a inflação, densidade de energia após este período, o tempo presente e o tamanho real do Universo estão de acordo com o modelo padrão de cosmologia. Uma interpretação da fase inflacionária como resultado do princípio de exclusão de Pauli também é possível se o campo de MDO for tratado como um valor médio de seu análogo quântico / Doutor

Le collisionneur linéaire international (ILC) est prévu pour être le prochain grand projet de la physique des hautes énergies. ILC est proposé avec deux détecteurs, International Large Detector (ILD), et Silicon Detector (SID). Cette thèse s’est déroulée dans le cadre de l'ILD. L'un des principaux composants du détecteur ILD est la chambre à projection temporelle (TPC). Cette thèse se concentre sur le développement de la lecture de la TPC, basée sur l'intégration des détecteurs de gaz Micro-pattern (Micromegas) et de puces CMOS pixels ("Timepix"). Ce nouveau type de dispositif est appelé "Ingrid". Les exigences principales pour "Ingrid" sont d’atteindre la sensibilité aux électrons uniques et d’obtenir une très haute résolution spatiale (~ 30 µm). Avec une TPC, on reconstruit les traces en utilisant le profil 2D des charges sur la plaque a l’extrémité de la TPC et la troisième coordonnée est dérivée du temps de dérive. Dans le cadre de cette thèse, une mini-TPC a été construite a Saclay dans le but de tester plusieurs prototypes de détecteurs "Ingrid". En outre, un système compose de 8 puces nommé "Octopuce" a été construit pour développer des algorithmes de reconstruction de traces. Nous avons effectué plusieurs mesures à l'aide de source radioactive à Saclay. Par ailleurs, de grands modules ont été testés avec un prototype de grande TPC (LP) sur un faisceau de test à DESY. Les résultats obtenus avec deux modules différents ont été présentés et les résultats sont en bon accord avec la prédiction théorique. La présence de la matière noire fournit une bonne indication d'apparition de nouveaux phénomènes a proximité de l'échelle électrofaible, et l'hypothèse populaire d’existence des WIMP doit être testé. Comme les couplages des WIMP aux différentes espèces de particules du modèle standard sont a priori inconnus, la recherche de la production de WIMP en collisions e+e- est complémentaire à la production dans les collisions pp ou a la détection directe de WIMPs primordiaux par leur diffusion sur des nucléons. Dans ce travail, nous étudions possibilité de découverte (ou l'exclusion) de production de paires de WIMPs avec l’ILC. Dans ce processus, un unique photon est rayonne dans l'état initial et une énergie manquante est requise. Nous montrons que l’ILC peut découvrir cette signature, même si l'annihilation en paires électron-positon contribue faiblement au taux d’annihilation de la matière noire dans l'univers primordial. Nous avons traduit la sensibilité en terme d’échelles de masse pour différents types d’opérateurs effectifs et montré que la masse et les couplages des WIMPs peuvent être mesurés avec une précision de l’ordre de 1% si leur détection est avérée. En outre, des études de production de WIMPs avec l’ILC sont complémentaires aux études avec des états finaux mono-X au LHC, car ils testent le couplage WIMP-lepton. Au LHC, le couplage WIMP-proton est testé a une l'échelle de 1 TeV. Avec l’ILC, en utilisant une luminosité intégrée de 500 fb⁻¹, une énergie dans le centre de masse de √s = 500 GeV et avec des faisceau non polarisés, une limite pour l’échelle sur l'interaction de contact Λ de l’ordre de 2 TeV est accessible. De plus, les configurations de polarisation appropriées permettent d'améliorer la sensibilité pour les recherches de matière noire à l’ILC, en supposant que le couplage des paires de WIMP aux électrons et aux positons dépend du choix de l'opérateur. / The International Linear Collider (ILC) is planned to be the next major project in the High Energy Physics. ILC is proposed to have two detectors, namely International Large Detector (ILD), and Silicon Detector (SiD). This thesis is done in the framework of the ILD. One of the main components of the ILD detector is the Time Projection Chamber (TPC). This PhD thesis concentrates on the development of TPC readout, based on integration of the Micro-pattern gas detectors (Micromegas) and CMOS pixel chips ("Timepix"). This new type of device is named "InGrid". Main requirements for "InGrid" is to achieve sensitivity to single electrons and a very high spatial resolution (~30 μm). In TPC one reconstructs tracks using 2D-charge profile on the TPC endplate and the third coordinate is derived from the drift time information. In Saclay mini-TPC was built. Using this mini-TPC, several prototype "Ingrid" detectors have been tested in the course of this PhD. In addition, 8-chips system named “Octopuce” was built to develop track reconstruction algorithms. We have performed several measurements using laboratory radioactive source in Saclay. In addition, the large modules were tested at a Large TPC Prototype (LP) in a test beam area at DESY. Results with two different modules were presented. Obtained results well agreed with theoretical prediction. The existence of Dark Matter provides a strong indication for the appearance of new phenomena near the electroweak scale, and the popular WIMP hypothesis is out there to be tested. Since the couplings of WIMPs to different species of Standard Model particles are a priori unknown, the investigation of WIMP production in e+e- collisions is fundamentally complementary to production in pp collisions or direct detection of primordial WIMPs scattering on nucleons. In this work we investigate the discovery (or exclusion) reach of the ILC based on the production of a pair of WIMPs, which recoils against an energetic photon from initial state radiation. We show that the ILC can discover this signature even if annihilation to electrons provides only a small fraction of the total dark matter annihilation rate in the early universe. We translated the sensitivity into mass scales of various effective operators and showed that the WIMPs mass and couplings can be measured at the percent level in case of an observation. Furthermore, WIMPs studies on ILC are complementary to current LHC in the mono-X final states, because they test WIMP-lepton coupling. LHC studies WIMP-proton coupling at the scale of 1 TeV. ILC could reach limits up to 2 TeV on the contact interaction scale Λ for the vector operator by using an integrated luminosity at 500 fb⁻¹, at the center-of-mass √s = 500 GeV with unpolarized beams. Moreover, proper polarization configurations allows to improve sensitivity for the Dark Matter searches at the ILC, assuming WIMPs pair couple differently to electron and positron for different operators.

Dark matter (DM), whose nature and interaction mechanisms are still an open issue, constitutes about 25 % of the Universe energy density. Weakly Interacting Massive Particles (WIMPs) are considered as strong candidates for particle DM and their search is conveniently carried out through the detection of gamma rays. The newly discovered ultra-faint dwarf spheroidal galaxies (dSphs), located in the vicinity of the Galaxy, exhibit high values of the mass to luminosity ratio, and are therefore considered as strongly dominated by DM. These objects are within reach of the Cherenkov Telescope Array (CTA), which is the future project for gamma-ray astronomy, with an better sensitivity (one order of magnitude) with respect to the current generation experiments. The main goal of the present work is the study of the sensitivity of CTA to WIMPs DM particles, by simulating the observation of the ultra-faint dwarf spherical galaxies Triangulum II, Reticulum II and Carina III, as well as of the classical dwarf galaxy Sculptor, for different annihilation channels, between 70 GeV and 100 TeV. The sensitivity curve in the WIMPs parameter space (velocity-averaged annihilation cross section < &sigma; &nu; > and DM mass mDM) was computed. We found that, within the sample of dwarf galaxies tested, Triangulum II is the most promising source, able to reach the thermal freeze-out values in the annihilation channel &tau;+&tau;- for only 50 hours of observation. Our result, the first estimation of the sensitivity for DM searches in ultra-faint dwarfs with CTA, is consistent with results from current generation experiments, showing better performance over an extended energy range. The limited sample of available stars in the targets induces uncertainties on the DM content. Future measurements, leading to a better understanding of the sources dynamic equilibrium, can improve this situation. Even so, the combination of the high DM content in the ultra-faint dwarf galaxies, together with the excellent expected performance of the future CTA, provides a promising result for indirect DM searches. / A matéria escura, cuja natureza e mecanismos de interação ainda estão em aberto, compõe 25% da densidade de energia do Universo. Weakly Interacting Massive Particles (WIMPs) apresentam-se como forte candidatas e sua busca é convenientemente conduzida através de raios gama. As recém descobertas galáxias esferoidais anãs ultra-fracas, situadas nos arredores da Galáxia, apresentam altos valores da razão entre massa e luminosidade, sendo portanto consideradas objetos fortemente dominados por matéria escura. Esses objetos estão ao alcance do Cherenkov Telescope Array (CTA), que é o futuro projeto da astronomia gama, com sensibilidade de uma order de grandeza melhor do que os experimentos atuais. O presente trabalho teve como objetivo estudar o potencial de detecção indireta de WIMPs através de raios gama com o futuro observatório CTA, observando as galáxias esferoidais anãs ultra-fracas Triangulum II, Retículum II e Carina III e a galáxia anã clássica Sculptor, para diferentes canais de aniquilação, entre 70 GeV e 100 TeV. A curva de sensibilidade no espaço de parâmetros livres de WIMPs (massa da partícula mDM e médida da seção de choque de aniquilação ponderada pela velocidade < &sigma; &nu; >) foi calculada. Nós encontramos que dentro da amostra de galáxias anãs testadas, Triangulum II é a fonte mais promissora, capaz de testar os valores térmicos no canal de aniquilação &tau;+&tau;- considerando apenas 50 horas de observação pelo CTA. Nosso resultado, a primeira estimativa da sensibilidade para busca de matéria escura em galáxias esferoidais anãs ultra-fracas com CTA, é consistente com resultados de experimentos da geração atual, e mostra um melhor desempenho em uma faixa de energia estendida. Os resultados são afetados pelas incertezas devido à pequena amostra de estrelas dos alvos escolhidos, que se reflete no conhecimento do conteúdo de matéria escura. Novas medidas podem ajudar a esclarecer essa situação. Ainda assim, a combinação de galáxias anãs ultra-fracas, aliada às melhorias do futuro CTA, apresenta-se como um passo muito promissor para buscas indiretas de matéria escura.

In experiments looking for rare events, like neutrinoless double beta decay (DBD0v) and dark matter search (DM), one of the main issues is to increase the experimental sensitivity through the material selection and production. In the specific the background contribution coming from the materials used for the detector realization has to be minimized. Moreover the net reduction of the background produced by the bulk part of the apparatus has raised concerns about the background contribution coming from the surfaces. Many procedures and techniques were developed during the last years in order to remove and to minimize the presence of possible contaminants on detector surfaces. To succeed in this strategy a big effort was put in defining all possible mechanisms that lead to surface contaminations, as well as specific cleaning procedures, which are able to reduce and control the surface radioactivity. The presence in air and gases of possible radioactive elements that can stick on the detector surfaces can lead to a recontamination process that will vanish all the applied cleaning procedures. Here is presented and analyzed the contribution to the background of rare events experiments like CUORE (DBD0v) and EDELWEISS (DM) produced by an exposure of their detector components to a big activity of 222Rn, radioactive daughter isotope from the 238U chain.

<p>Most of the matter in the Universe appears to be in some form which does not emit or absorb light. While evidence for the existence of this dark matter has accumulated over the last seventy years, its nature remains elusive. In this thesis, quasars and low surface brightness galaxies (LSBGs) are used to investigate the properties of the dark matter. </p><p>Quasars are extremely bright light sources which can be seen over vast distances. These cosmic beacons may be used to constrain dark matter in the form of low-mass, compact objects along the line of sight, as such objects are expected to induce brightness fluctuations in quasars through gravitational microlensing effects. Using a numerical microlensing model, we demonstrate that the uncertainty in the typical size of the optical continuum-emitting region in quasars represents the main obstacle in this procedure. We also show that, contrary to claims in the literature, microlensing fails to explain the observed long-term optical variability of quasars. Here, quasar distances are inferred from their redshifts, which are assumed to stem from the expansion of the Universe. Some astronomers do however defend the view that quasar redshifts could have a different origin. A number of potential methods for falsifying claims of such non-cosmological redshifts are proposed. </p><p>As the ratio of dark to luminous matter is known to be unusually high in LSBGs, these objects have become the prime targets for probing dark matter halos around galaxies. Here, we use spectral evolutionary models to constrain the properties of the stellar populations in a class of unusually blue LSBGs. Using rotation curve data obtained at the ESO Very Large Telescope, we also investigate the density profiles of their dark halos. We find our measurements to be inconsistent with the predictions of the currently favoured cold dark matter scenario.</p>

Big Bang Nucleosynthesis (BBN), together with the analyses of the Cosmic Microwave Background (CMB) anisotropies, confirm what our day to day experience of life attests : antimatter is far less present than matter in the Universe. In addition, these observables also permit to evaluate that there exists about one proton for every 10^{10} photons present in the Universe. This is in contradiction with expectations coming from the standard hot big bang, where no distinction between matter and antimatter is made, and where subsequent annihilations would lead to equal matter and antimatter contents, at a level 10^{−10} smaller than the observed one. The Standard Model of fundamental interactions fails to explain this result, leading us to search for ‘Beyond the Standard Model’ physics. Among the possible mechanism which could be responsible for the creation of such a matter asymmetry, leptogenesis is particularly attractive because it only relies on the same ingredients previously introduced to generate neutrino masses. Unfortunatelly, this elegant proposal suffers from a major difficulty : it resists to any tentative of being probed by our low energy observables. In this thesis, we tackle the problem the other way around and propose a way to falsify this mechanism. Considering the type-I leptogenesis mechanism, i.e. a mechanism based on the asymmetric decay of right-handed neutrinos, in a left-right symmetric framework, we show that the observation of a right-handed gauge boson W_R at future colliders would rule out any possibility for such mechanism to be responsible of the matter asymmetry present in our Universe. Another intriguing question that analyses of the anisotropies of the CMB confirmed is the presence of a non-baryonic component of matter in our Universe, i.e. the dark matter. As hinted by observations of galactic rotation curves, it should copiously be present in our galactic halo, but is notoriously difficult to detect directly. We can take advantage on the fact that antimatter almost disappeared from our surroundings to detect the contamination of cosmic rays from standard sources the annihilation products of dark matter would produce. The second subject tackled in this work is the study of the imprints the Inert Doublet Modem (IDM) could leave in (charged) cosmic rays, namely positrons, antprotons and antideuterons. This model, first proposed to allow the Bout-Englert-Higgs particle to evade the Electroweak Precision Test (EWPT) measurements, introduces an additional scalar doublet which is inert in the sense that it does not couple directly to fermions. This latter property brings an additional virtue to this additional doublet : since it interacts weakly with particles, it can play the role of dark matter. This study will be done in the light of the data recently released by the PAMELA, ATIC and Fermi-GLAST collaborations, which reported e^± excesses in two different energy ranges.

Most of the matter in the Universe appears to be in some form which does not emit or absorb light. While evidence for the existence of this dark matter has accumulated over the last seventy years, its nature remains elusive. In this thesis, quasars and low surface brightness galaxies (LSBGs) are used to investigate the properties of the dark matter. Quasars are extremely bright light sources which can be seen over vast distances. These cosmic beacons may be used to constrain dark matter in the form of low-mass, compact objects along the line of sight, as such objects are expected to induce brightness fluctuations in quasars through gravitational microlensing effects. Using a numerical microlensing model, we demonstrate that the uncertainty in the typical size of the optical continuum-emitting region in quasars represents the main obstacle in this procedure. We also show that, contrary to claims in the literature, microlensing fails to explain the observed long-term optical variability of quasars. Here, quasar distances are inferred from their redshifts, which are assumed to stem from the expansion of the Universe. Some astronomers do however defend the view that quasar redshifts could have a different origin. A number of potential methods for falsifying claims of such non-cosmological redshifts are proposed. As the ratio of dark to luminous matter is known to be unusually high in LSBGs, these objects have become the prime targets for probing dark matter halos around galaxies. Here, we use spectral evolutionary models to constrain the properties of the stellar populations in a class of unusually blue LSBGs. Using rotation curve data obtained at the ESO Very Large Telescope, we also investigate the density profiles of their dark halos. We find our measurements to be inconsistent with the predictions of the currently favoured cold dark matter scenario.

Astrophysical data analysis of the weak-field predictions support the claim that modified gravity (MOG) theories provide a self-consistent, scale-invariant, universal description of galaxy rotation curves, without the need of non-baryonic dark matter. Comparison to the predictions of Milgrom's modified dynamics (MOND) provide a best-fit and experimentally determined universal value of the MOND acceleration parameter. The predictions of the modified gravity theories are compared to the predictions of cold non-baryonic dark matter (CDM), including a constant density core-modified fitting formula, which produces excellent fits to galaxy rotation curves including the low surface brightness and dwarf galaxies. Upon analysing the mass profiles of clusters of galaxies inferred from X-ray luminosity measurements, from the smallest nearby clusters to the largest of the clusters of galaxies, it is shown that while MOG provides consistent fits, MOND does not fit the observed shape of cluster mass profiles for any value of the MOND acceleration parameter. Comparison to the predictions of CDM confirm that whereas the Navarro-Frenk-White (NFW) fitting formula does not fit the observed shape of galaxy cluster mass profiles, the core-modified dark matter fitting formula provides excellent best-fits, supporting the hypothesis that baryons are dynamically important in the distribution of dark matter halos.