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Lin, Tongyan. "Signals of Particle Dark Matter." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10273.
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This thesis explores methods of detecting dark matter particles, with some emphasis on several dark matter models of current interest. Detection in this context means observation of an experimental signature correlated with dark matter interactions with Standard Model particles. This includes recoils of nuclei or electrons from dark matter scattering events, and direct or indirect observation of particles produced by dark matter annihilation.Physics
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Stref, Martin. "Dark Matter on the Galactic Scale : from Particle Physics and Cosmology to Local Properties." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS077/document.
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Identifier la nature de la matière sombre est l'un des plus grands problèmes de la physique contemporaine. Si la matière sombre est constituée de particules, on peut espérer la détecter, directement ou indirectement, grâce à des expériences terrestres ou spatiales. Prédire les résultats de ces expériences, ou les interpréter en cas de détection, nécessite une compréhension profonde de la structuration de la matière sombre dans notre Galaxie. En partant de considérations issues de la physique des particules et de la cosmologie, je construits un modèle du halo de matière sombre Galactique contraint dynamiquement qui incorpore une description détaillée des ses inhomogénéités. L'impact des ces inhomogénéités sur les recherches utilisant le rayonnement cosmique est ensuite analysé en détails. J'étudie également une méthode permettant de prédire la distribution dans l'espace des phases des particules de matière sombre, et discute sa possible application aux recherches de matière sombre. Cet outil est ensuite appliqué aux recherches utilisant les électrons et positrons cosmiques, et de nouvelles contraintes très fortes sont obtenues sur les modèles microscopiques de matière sombreUnderstanding the nature of dark matter is one of the greatest challenges of modern physics. If dark matter is made of particles, we can hope to detect it, directly or indirectly, using Earth-based or spatial experiments. Make predictions for the outcome of these experiments, or interpret the results in case of a detection, requires a deep understanding of the structuring of dark matter in our Galaxy. Starting from particle physics and cosmological considerations, I built a dynamically constrained model of the Galactic dark halo including a detailed description of its inhomogeneities. The impact of these inhomogeneities on searches with cosmic rays is then analysed in details. I also study a method allowing to predict the phase-space distribution of dark matter particles, and discuss its possible application to dark matter searches. This method is then applied to searches with cosmic-ray electrons and positrons, and new very stringent constraints are obtained on microscopic models of dark matter
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Taoso, Marco. "Particle dark matter and astrophysical constraints." Doctoral thesis, Paris 7, 2009. http://www.theses.fr/2009PA077262.
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De nombreuses observations astrophysiques et cosmologiques indiquent l'existence de Matière Noire non-baryonique dans l'Univers. Sa présence est bien établie à différentes échelles, des galaxies aux structures à grande échelle et aux échelles cosmologiques. Toutefois, malgré ces nombreux indices indépendants, la nature de la matière noire demeure aujourd'hui encore inconnue. Parmi les nombreux candidats proposés, les WIMPs (acronyme de l'anglais Weakly Interacting Massive Particles) sont les plus populaires. Dans cette thèse, nous étudions les perspectives de détection indirect des WIMPs. Nous considerons grandes concentrations de Matière Noire que il peut avoir autour de trous noirs de masse intermédiaire et nous étudions les perspectives de détection des rayons gamma produits par l'annihilation de WIMPs. Nous examinons aussi la recherche indirect de WIMPs dans les flux des rayons cosmiques. Enfin, nous montrons que les annihilations de WIMPs pourraient modifier radicalement l'évolution des premières étoilesNumerous astrophysical and cosmological observations support the existence of non-baryonic Dark Matter in the Universe. Its presence is well established at different scales, from galaxies to large scale structures and cosmological scales. However, despite the numerous and independent evidences, the nature of Dark Matter in not yet understood. Among the large number of Dark Matter candidates proposed in literature, Weakly Interacting Massive Particles (WIMPs) are the most popular. In this thesis we study the prospect for indirect detection of WIMPs. We first focus on searches of large DM overdensities around Intermediate Mass Black Holes with gamma-ray experiments. We then consider DM searches in the antimatter cosmic-ray fluxes and finally we study the impact of WIMPs annihilations in the evolution of the first stars
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Scott, Pat. "Searches for Particle Dark Matter Dark stars, dark galaxies, dark halos and global supersymmetric fits /." Doctoral thesis, Stockholm : Department of Physics, Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38221.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Accepted. Paper 6: Submitted. Härtill 6 uppsatser.
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Alp, Dennis, and Samuel Modée. "Dark Matter: Particle Evolution through Freeze-out." Thesis, KTH, Teoretisk fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145892.
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This report focuses on the evolution of dark matter particles in a simplied, homogeneous and isotropic model of the Universe. The purpose is to analyze theoretical predictions and recent experimental measurements to be able to draw conclusions about the properties of the dark matter particles. The inexperienced reader is introduced to the subject and thorough derivations of the formulas relevant to the analysis are made. To analyze the evolution of dark matter, the Boltzmann equation is applied to a freeze-out model. Both analytical and numerical approaches will be taken and discrepancies between those are investigated. Qualitative eects of the particle cross section and mass are studied and constraints on the parameters are set using experimental data. Finally, assumptions are discussed and suggestions for further research are made.Rapporten fokuserar på utvecklingen av mörk materia-partiklar i en förenklad, homogen och isotrop modell av universum. Syftet är att analysera teoretiska förutsägelser och nyligen genomförda experimentella mätningar för att dra slutsatser om mörk materiapartiklarnas egenskaper. Den oerfarne läsaren introduceras till ämnet och en utförlig härledning av de relevanta formlerna genomförs. Boltzmannekvationen tillämpas på en utfrysningsmodell och används för att analysera utvecklingen av den mörka materian. Både analytiska och numeriska metoder används och skillnader mellan dessa studeras. Kvalitativa eekter av partiklarnas tvärsnitt och massa undersöks och begränsningar av parametrarna görs med hjälp av experimentell data. Slutligen diskuteras antaganden och förslag för fortsatt forskning läggs fram.
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Shuve, Brian. "Dark and Light: Unifying the Origins of Dark and Visible Matter." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10303.
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The Standard Model of particle physics can account for neither the dark matter dominating the universe's matter density, nor the baryon asymmetry that leads to the visible matter density. This dissertation explores models of new physics that connect dark matter to baryogenesis and can naturally account for the observed quantities of both types of matter. Special emphasis is given to models incorporating new weak-scale physics, as such models often predict signatures at present and upcoming experiments and can potentially be connected to solutions of the hierarchy problem. In one class of models we study, the dark matter abundance is determined by a dark matter asymmetry connected to the baryon asymmetry. In such models, the separate dark matter, baryon, and lepton number global symmetries observed today are individually broken at or above the weak scale and lead to mixing of dark matter and Standard Model fields in the early universe. This can happen generically, with dark matter-visible matter mass mixing induced by large background energies or moduli in the early universe, and can also arise at the electroweak phase transition. Mass mixing models of asymmetric dark matter can readily accommodate dark matter masses ranging from 1 GeV to 100 TeV and expand the scope of possible relationships between the dark and visible sectors. We also consider models of symmetric dark matter in which the annihilation of dark matter particles in the early universe generates the observed baryon asymmetry. This process, called “WIMPy baryogenesis”, naturally accommodates weak-scale dark matter and explains the observed dark matter density with only order-one couplings. WIMPy baryogenesis is a new model of baryogenesis at the weak scale, avoiding problems with high reheat temperatures in supersymmetric theories, and yielding observable consequences in ongoing and future experiments for some modelsPhysics
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Vannerom, David. "Search for new physics in the dark sector with the CMS detector: From invisible to low charge particles." Doctoral thesis, Universite Libre de Bruxelles, 2019. https://dipot.ulb.ac.be/dspace/bitstream/2013/293380/4/thesis.pdf.
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The Standard Model of particle physics is the framework that describes all known phenomenaand interactions between elementary particles. It has proven to give outstanding results overthe years and was succesfully completed with the discovery of the Brout-Englert-Higgs boson in2012 by the ATLAS and CMS collaborations at CERN. However, several observations escape itsreach: the matter-antimatter asymmetry, the nature of Dark Matter or the quantization of theelectric charge. These are all examples of measured facts not explained by the Standard Modelformalism and that call for an extension to a Beyond the Standard Model (BSM) theory. In thisthesis, we have looked for evidence of new physics using proton-proton collision data producedby CERN’s Large Hadron Collider (LHC) at a center-of-mass energy of 13 TeV. Collected from2016 to 2018 by the CMS detector, it corresponds to an integrated luminosity of 136/fb .Afteran introduction to the theoretical context and the experimental tools, two analyses are presented.The first one is a search for Dark Matter particles recoiling against a jet and leaving the detectorunnoticed. With this ”monojet” analysis, we are able to exclude mediator masses up to 1.8TeV, and masses of Dark Matter particles up to 700 GeV. The second analysis is a search forfractionally charged particles. Using the fact that their stopping power is lower than StandardModel particles, we are able to exclude their existence up to masses of 765 GeV for a charge of2/3 e.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Hahn, Andreas. "Particle detection with superconducting phonon sensors." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259881.
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Strege, Charlotte. "Characterization of particle dark matter via multiple probes." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24924.
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The dark matter problem is one of the most striking puzzles in physics today. Cosmological and astrophysical observations have provided strong evidence that over 80% of the matter in the Universe is dark. However, direct proof for the existence of dark matter particles from laboratory experiments is still lacking, so that the physical nature of dark matter remains unknown. Possible solutions are found in theoretical models of new physics, which propose new particles that are excellent dark matter candidates, thus presenting a fundamental connection between elementary particle physics and the astrophysical dark matter. In this thesis, I adopt a multi-messenger approach towards the identification and characterisation of the dark matter particle. I apply advanced statistical and numerical techniques to probe theoretical models and derive robust constraints on the nature and properties of dark matter in light of the full range of existing experimental results. I present global fits analyses of three models of supersymmetry (the cMSSM, the NUHM and the MSSM-15), including data from collider searches for new physics, cosmology experiments, astro-particle dark matter searches, and the Higgs boson discovery. A strong complementarity between the LHC and astro-particle experiments is observed, highlighting the benefits of a combined analysis. I find that constrained models, such as the cMSSM and the NUHM, that were appropriate targets for global fits prior to the start of LHC operations, have been placed under strong pressure by recent data sets. I present the first statistically convergent profile likelihood maps of a 15-dimensional MSSM, which is only weakly constrained by the existing data, and is a much more suitable framework for phenomenological studies of supersymmetry. I derive robust and statistically meaningful constraints on the supersymmetric parameters and dark matter properties in this model. Detection prospects for the cMSSM and the NUHM are positive, while fully probing the rich phenomenology of the MSSM-15 is more difficult. I present the regions of the parameter spaces that are most promising to explore with future searches and pinpoint the signatures characteristic of supersymmetric dark matter in these models. A very effective experimental strategy is the direct detection of dark matter. I explore the statistical limitations of next-generation direct detection experiments in the case of a significant detection. I find that the uncertainty and bias in the reconstructed WIMP properties is particularly severe for heavy WIMPs, but can also be significant for intermediate-mass WIMPs leading to several hundreds of events. I demonstrate that the precision and accuracy of the WIMP characterisation can be considerably improved by exploiting the complementarity between different target materials, and by increasing the experimental exposure.
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Colburn, Russell J. III. "Beyond the Standard Model: Dark Matter and Collider Physics." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1507215920939059.
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Sivertsson, Sofia. "Studies of dark matter in and around stars." Doctoral thesis, KTH, Teoretisk partikelfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-64245.
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There is by now compelling evidence that most of the matter in the Universe is in the form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models, dark matter particles can annihilate with each other into standard model particles; the direct or indirect observation of such annihilation products could give important clues for the dark matter puzzle. For signals from dark matter annihilations to be detectable, typically high dark matter densities are required. Massive objects, such as stars, can increase the local dark matter density both via scattering off nucleons and by pulling in dark matter gravitationally as a star forms. Annihilations within this kind of dark matter population gravitationally bound to a star, like the Sun, give rise to a gamma ray flux. For a star which has a planetary system, dark matter can become gravitationally bound also through gravitational interactions with the planets. The interplay between the different dark matter populations in the solar system is analyzed, shedding new light on dark matter annihilations inside celestial bodies and improving the predicted experimental reach. Dark matter annihilations inside a star would also deposit energy in the star which, if abundant enough, could alter the stellar evolution. This is investigated for the very first stars in the Universe. Finally, there is a possibility for abundant small scale dark matter overdensities to have formed in the early Universe. Prospects of detecting gamma rays from such minihalos, which have survived until the present day, are discussed.Kosmologiska observationer har visat att större delen av materian i universum består av mörk materia, en form av materia med helt andra egenskaper än den vi upplever i vardagslivet. Effekterna av denna mörka materia har observerats gravitationellt på många olika sätt men vad den egentligen består av är fortfarande okänt. I de flesta modeller kan mörk materia-partiklar annihilera med varandra till standardmodellpartiklar. Att direkt eller indirekt observera sådana annihilationsprodukter kan ge viktiga ledtrådar om vad den mörka materian består av. För att kunna detektera sådana signaler fordras typiskt höga densiteter av mörk materia. Stjärnor kan lokalt öka densiteten av mörk materia, både via spridning mot atomkärnor i stjärnan och genom den ökande gravitationskraften i samband med att en stjärna föds. Annihilationer inom en sådan mörk materia-population gravitationellt bunden till en stjärna, till exempel solen, ger upphov till ett flöde av gammastrålning, som beräknas. För en stjärna som har ett planetsystem kan mörk materia även bli infångad genom gravitationell växelverkan med planeterna. Samspelet mellan de två mörk materia-populationerna i solsystemet analyseras, vilket ger nya insikter om mörk materia-annihilationer inuti himlakroppar och förbättrar de experimentella möjligheterna att detektera dem. Mörk materia-annihilationer inuti en stjärna utgör också en extra energikälla för stjärnan, vilket kan påverka stjärnans utveckling om mörk materia-densiteten blir tillräckligt stor. Denna effekt undersöks för de allra första stjärnorna i universum. Slutligen finns det också en möjlighet att det i det tidiga universum skapades mörk materia-ansamlingar som fortfarande finns kvar idag. Utsikterna att upptäcka dessa genom mätning av gammastrålning diskuteras.
QC 20120130
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Phelps, Patrick. "THE LUX DARK MATTER EXPERIMENT: DETECTOR PERFORMANCE AND ENERGY CALIBRATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1404908222.
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Robbins, Glenn. "New Physics at Colliders and in Space." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1149/document.
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La quête de la nouvelle physique est un défi impliquant à la fois la recherche de particules de matière noire dans les halos galactiques, et celle, aux collisonneurs, de particules dont l’existence est prédite par des théories au-delà du Modèle Standard, telles que la supersymétrie. Alors que les contraintes expérimentales sur ces particules s’intensifient, il devient capital de combiner les limites provenant de ces deux volets afin de guider la suite des recherches. Pour ce faire, il est indispensable d’évaluer et de tenir compte correctement des incertitudes astrophysiques, cosmologiques et nucléaires, pourtant souvent ignorées. La première partie de cette thèse est dédiée à l’étude de ces incertitudes et leur impact sur les contraintes obtenues en supersymétrie, ainsi que la complémentarité entre les contraintes des collisionneurs et de matière noire pour la recherche de nouvelle physique. La deuxième partie est consacrée au développement d’outils de calculs pour les détections directe et indirecte de matière noire, conçus afin de prendre correctement en compte les incertitudes astrophysiques et nucléaires, et à leur implémentation dans le code public SuperIso Relic. Enfin la troisième partie du travail concerne l’étude des implications cosmologiques d’une éventuelle découverte de nouvelles particules aux collisionneurs. Nous avons montré qu’il serait possible de tester les hypothèses du modèle cosmologique standard et d’obtenir des informations sur les propriétés de l’Univers primordial à une époque observationnellement inaccessibleThe quest for new physics is a challenging task which involves, on the one hand, the search for dark matter particles from space, and on the other hand, the search at colliders for particles predicted by theories beyond the Standard Model, such as supersymmetry. With the experimental constraints on new particles getting stronger, it becomes crucial to combine the limits from both sectors in order to guide future searches. To this end, it is essential to estimate and take into account correctly the astrophysical, nuclear and cosmological uncertainties, which are most often ignored. The first part of this thesis is dedicated to the study of such uncertainties and to their impact on the constraints applied on supersymmetry. Moreover, we investigate the interplay between the constraints from colliders and dark matter searches in some detail. The second part concerns the development and the implementation in the public code SuperIso Relic of numerical tools for the calculation of direct and indirect dark matter detection constraints which were designed specifically to take correctly into account astrophysical and nuclear uncertainties. Finally, in the third part of this work, we consider the cosmological implications of a hypothetical discovery of new particles at colliders. We show that it would be possible to test the assumptions of the standard cosmological model and to obtain information on the properties of the primordial Universe at an epoch which is beyond observational reach
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Ng, Chun Yu. "Seeking the Light in the Dark: Quests for Identifying Dark Matter." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471363029.
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Love, Christina Elena. "Design and Analysis for the DarkSide-10 Two-Phase Argon Time Projection Chamber." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/214821.
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PhysicsPh.D.
Astounding evidence for invisible "dark" matter has been found from galaxy clusters, cosmic and stellar gas motion, gravitational lensing studies, cosmic microwave background analysis, and large scale galaxy surveys. Although all studies indicate that there is a dominant presence of non-luminous matter in the universe (about 22 percent of the total energy density with 5 times more dark matter than baryonic matter), its identity and its "direct" detection (through non-gravitational effects) has not yet been achieved. Dark matter in the form of massive, weakly interacting particles (WIMPs) could be detected through their collisions with target nuclei. This requires detectors to be sensitive to very low-energy (less than 100 keV) nuclear recoils with very low expected rates (a few interactions per year per ton of target). Reducing the background in a direct dark matter detector is the biggest challenge. A detector capable of seeing such low-energy nuclear recoils is difficult to build because of the necessary size and the radio- and chemical- purity. Therefore it is imperative to first construct small-scale prototypes to develop the necessary technology and systems, before attempting to deploy large-scale detectors in underground laboratories. Our collaboration, the DarkSide Collaboration, utilizes argon in two-phase time projection chambers (TPCs). We have designed, built, and commissioned DarkSide-10, a 10 kg prototype detector, and are designing and building DarkSide-50, a 50 kg dark matter detector. The present work is an account of my contribution to these efforts. The two-phase argon TPC technology allows powerful discrimination between dark matter nuclear recoils and background events. Presented here are simulations, designs, and analyses involving the electroluminescence in the gas phase from extracted ionization charge for both DarkSide-10 and DarkSide-50. This work involves the design of the HHV systems, including field cages, that are responsible for producing the electric fields that drift, accelerate, and extract ionization electrons. Detecting the ionization electrons is an essential element of the background discrimination and gives event location using position reconstruction. Based on using COMSOL multiphysics software, the TPC electric fields were simulated. For DarkSide-10 the maximum radial displacement a drifting electron would undergo was found to be 0.2 mm and 1 mm for DarkSide-50. Using the electroluminescence signal from an optical Monte Carlo, position reconstruction in these two-phase argon TPCs was studied. Using principal component analysis paired with a multidimensional fit, position reconstruction resolution for DarkSide-10 was found to be less than 0.5 cm and less than 2.5 cm for DarkSide-50 for events occurring near the walls. DarkSide-10 is fully built and has gone through several campaigns of operation and upgrading both at Princeton University and in an underground laboratory (Gran Sasso National Laboratory in Assergi, Italy). Key DarkSide two-phase argon TPC technologies, such as a successful HHV system, have been demonstrated. Specific studies from DarkSide-10 data including analysis of the field homogeneity and the field dependence on the electroluminescence signal are reported here.
Temple University--Theses
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McCabe, Christopher. "Aspects of dark matter phenomenology." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:74ec0d09-40d6-481d-b2ec-d0e9d41d5c1d.
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Identifying the relic particles that constitute the cold dark matter in our Universe is an outstanding problem in astro-particle physics. Direct detection experiments are among the most promising methods of detecting particle dark matter through non-gravitational interactions. In this thesis, the usual assumptions made when calculating the event rate at direct detection experiments are examined. Varying astrophysical parameters and the dark matter velocity distribution leads to significant changes in acceptance regions and exclusion curves for scenarios in which the tail of the velocity distribution is sampled; this includes 'light dark matter' (mass less than 10 GeV) and 'inelastic dark matter'. The DAMA and CoGeNT collaborations both report an annual modulation in their event rate that they attribute to dark matter. Two analyses of these experiments are performed. In the first, it is shown that these experiments can be compatible with each other and with the constraints from other direct detection experiments. This requires some isospin violation in the couplings of dark matter to protons and neutrons and a small inelastic splitting to boost the modulation fraction. The second analysis provides a comparison of the modulation signals free from all astrophysical parameters, under the assumption that dark matter scatters elastically. Again it is found that some isospin violation and a boosted modulation fraction is required in order that DAMA and CoGeNT are consistent with all experiments. A boosted modulation fraction may arise from a velocity distribution different from the Maxwell-Boltzmann distribution, which is usually assumed. Finally, a supersymmetric theory in which the dark matter candidate is a mixture of left- and right-handed sneutrino is considered. This theory has many novel signatures at colliders, indirect detection and direct detection experiments.
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Minaeva, Yulia. "Serch for Neutralino Dark Matter with the AMANDA-II Neutrino Telescope." Doctoral thesis, Stockholm University, Department of Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-137.
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The annihilation of weakly interacting massive particles (WIMPs), accumulated in gravitational potentials (e.g., the core of the Earth, the Sun or the Galactic halo) would lead to neutrino production. This thesis investigates the possibility of searching for WIMPs in the form of the lightest supersymmetric particle (neutralino) trapped in the Sun using the AMANDA-II neutrino telescope. AMANDA-II is a large Cherenkov detector located deep in the ice at the geographical South Pole. The presented work is based on data taken during the year 2001. An analysis optimized to search for the neutralino-induced flux from the Sun has been developed. The observation of no excess with respect to the expected atmospheric neutrino background has been interpreted as an upper limit on the neutralino annihilation rate in the Sun and on the neutralino-induced muon flux in the vicinity of the detector.
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Appagere, Grandharva. "Can Feebly Interacting Massive Particles (FIMP) constitute Dark Matter?" Thesis, KTH, Fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298420.
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In this study, we investigate the feasibility of Feebly Interacting Massive particles (FIMP) as possible candidates to constitute the observed Dark Matter abundance in the universe. FIMPs are particles that couple very feebly with known particles in the Standard Model (SM). As such, they do not attain thermal equilibrium with the baryon abundant environment in the early universe before Nucleosynthesis. In contrast to a freeze-out mechanism common for Weakly Interacting Massive Particles (WIMP) as DM candidates, FIMPs are produced by the so-called freeze-in mechanism that we will describe in this study. The purpose of this study is to investigate how the Coleman Weinberg (C-W) mechanism affects the FIMP [freeze-in] mechanism. We specifically consider a minimal extension of SM in which an Electroweak Singlet-scalar ($S$) couples only to the Higgs-boson ($H$); This is called the Higgs-portal mechanism. We study the C-W effective potentials for the Higgs and Dark-scalar singlet and their implications on FIMP mechanism.Using these, we focus on the High-temperature production of the DM with just the $HH\mapsto SS$ to compute the reaction rates, comparing Bose-Einstein statistics ($\Gamma_{HH\mapsto S S}^{B-E}$) to Maxwell-Boltzmann statistics $\Gamma_{HH\mapsto S S}^{M-B}$. We employ only $\Gamma_{HH\mapsto S S}^{B-E}$ to compute DM relic abundance ($Y$) at several Dark-scalar masses ($m_S$) as a function of coupling $k$, establishing that Higgs-Dark scalar coupling $k$ $\mapsto$ $k_{DM}$ corresponding to actual DM abundance lies in between ${10}^{-8.7}$ and ${10}^{-8}$, i.e. ${10}^{-8.7}<k_{DM}<="" div="">I denna studie undersöker vi mycket svagt interagerande massiva partiklar (FIMP) som möjliga kandidater till den observerade mängden av mörk materia i universum. FIMP:er är partiklar som interagerar väldigt svagt med de kända partiklarna i Standarmodellen (SM). Som sådana uppnår de ej termisk jämvikt med den baryonrika omgivningen i det tidiga universumet innan nukleosyntes sker. I kontrast med en frys-ut mekanism vanligt för svagt interagerade massiva partiklar (WIMPS) som DM kandidater, så produceras FIMP:er av en så kallad frys-in mekanism som vi skall beskriva i denna studie. Syftet med studien är att undersöka hur Coleman Weinberg (C-W) mekanismen påverkar frys-in mekanismen för FIMP:er. Vi tar särskilt hänsyn till en minimal utvidgning av SM i vilken en Elektrosvag singlettskalär ($S$) interagerar med endast Higgsbosonen. Denna mekanism kallas för Higgs-portalmekanism. Vi studerar de C-W effektiva pontetialerna för higgs och mörk-skalärsingletten och deras implikationer för FIMPmekanismen. När vi använder dessa, så fokuserar vi på högtemperatursproduktion av DM med endast $HH\mapsto SS$ för att beräkna reaktionshastigheter, och jämför Bose-Einstein statistik ($\Gamma_{HH\mapsto S S}^{B-E}$) med Maxwell-Boltzmann statistik $\Gamma_{HH\mapsto S S}^{M-B}$. Vi använder endast $\Gamma_{HH\mapsto S S}^{B-E}$ för att beräkna kvarvarande DM mängd ($Y$) för flera mörk-skalärmassor ($m_S$) som en funktion av interaktion $k$, vilket slår fast att Higgs-Mörk skalär interaktionen $k$ $\mapsto$ $k_{DM}$ som korresponderar mot den faktiska DM mängden ligger mellan ${10}^{-8.7}$ and ${10}^{-8}$, i.e. ${10}^{-8.7}<k_{DM}<="" div="">
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Angus, Stephen Andrew. "Phenomenology of dark radiation and string compactifications." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:739ffcb2-bf9d-4fd3-8d6c-911d2d599f5e.
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In this Thesis I explore aspects of dark radiation and its role in String Phenomenology. Dark radiation is any additional hidden type of relativistic matter present in the Universe today, conventionally labelled as an "excess effective number of neutrino species", Δ Neff. It provides a powerful test of hitherto untested theoretical models based on fundamental theories such as String Theory. I begin by considering dark radiation in the LARGE Volume Scenario, a phenomenologically viable class of string compactifications. First I review how the minimal setup slightly overproduces axionic dark radiation via modulus decay. I then demonstrate that loop corrections to the main competing visible-sector decay process have a negligible effect and are unable to alleviate the tension with observations. In the following chapter I explore fibred extensions of the LARGE Volume Scenario. The predictions for Δ Neff are qualitatively different: in particular, models with a sequestered visible sector on D3 branes at a singularity are swamped by massless axions and decisively ruled out. I then consider TeV-scale supersymmetry in a model with anisotropic modulus stabilisation. If the Standard Model is realised on D7 branes wrapping the small volume cycle a hierarchy of soft terms is generated, which may have applications to natural supersymmetry. The final chapter takes a different approach and investigates the proposition that dark radiation, in the form of a Cosmic Axion Background, could explain the long-standing soft X-ray excess from galaxy clusters. I show for the Coma cluster that the morphology of the excess can be reproduced by axion-photon conversion in the intracluster magnetic field, provided the field is allowed to have more structure on smaller scales than typically assumed based on Faraday rotation data. This explanation requires an inverse axion-photon coupling M ∼ 1011 - 1012 GeV and a mean axion energy (ECAB) ∼ 50 - 250 eV.
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Unwin, James. "On connections between dark matter and the baryon asymmetry." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:5d7d6d06-5ef8-4921-8d4f-9ab19e21a031.
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This thesis is dedicated to the study of a prominent class of dark matter (DM) models, in which the DM relic density is linked to the baryon asymmetry, often referred to as Asymmetric Dark Matter (ADM) theories. In ADM the relic density is set by a particle-antiparticle asymmetry, in direct analogue to the baryons. This is partly motivated by the observed proximity of the baryon and DM relic densities Ω_{DM} ≈ 5 Ω_{B}, as this can be explained if the DM and baryon asymmetries are linked. A general requisite of models of ADM is that the vast majority of the symmetric component of the DM number density, the DM-antiDM pairs, must be removed for the asymmetry to set the DM relic density and thus to explain the coincidence of Ω_{DM} and Ω_{B}. However we shall argue that demanding the efficient annihilation of the symmetric component leads to a tension with experimental constraints in a large class of models. In order to satisfy the limits coming from direct detection and colliders searches, it is almost certainly required that the DM be part of a richer hidden sector of interacting states. Subsequently, examples of such extended hidden sectors are constructed and studied, in particular we highlight that the presence of light pseudoscalars can greatly aid in alleviating the experimental bounds and are well motivated from a theoretical stance. Finally, we highlight that self-conjugate DM can be generated from hidden sector particle asymmetries, which can lead to distinct phenomenology. Further, this variant on the ADM scenario can circumvent some of the leading constraints.
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Cunnama, Daniel. "Galaxy Evolution and Cosmology using Supercomputer Simulations by Daniel Cunnama." University of the Western Cape, 2013. http://hdl.handle.net/11394/4042.
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Philosophiae Doctor - PhDNumerical simulations play a crucial role in testing current cosmological models of the formation and evolution of the cosmic structure observed in the modern Universe. Simulations of the collapse of both baryonic and non-baryonic matter under the influence of gravity have yielded important results in our understanding of the large scale structure of the Universe. In addition to the underlying large scale structure, simulations which include gas dynamics can give us valuable insight into, and allow us to make testable predictions on, the nature and distribution of baryonic matter on a wide range of scales. In this work we give an overview of cosmological simulations and the methods employed in the solution of many body problems. We then present three projects focusing on scales ranging from individual galaxies to the cosmic web connecting clusters of galaxies thereby demonstrating the potential and diversity of numerical simulations in the fields of cosmology and astrophysics. We firstly investigate the environmental dependance of neutral hydrogen in the intergalactic medium by utilising high resolution cosmological hydrodynamic simulations in Chapter 3. We find that the extent of the neutral hydrogen radial profile is dependant on both the environment of the galaxy and its classification within the group ie. whether it is a central or satellite galaxy. We investigate whether this effect could arise from ram pressure forces exerted on the galaxies and find good agreement between galaxies experiencing high ram pressure forces and those with a low neutral hydrogen content. In Chapter 4 we investigate the velocity–shape alignment of clusters in a dark matter only simulation and the effect of such an alignment on measurements of the kinetic Sunyaev–Zeldovich (kSZ) effect. We find an alignment not only exists but can lead to an enhancement in the kSZ signal of up to 60% when the cluster is orientated along the line-of-sight. Finally we attempt to identify shocked gas in clusters and filaments using intermediate resolution cosmological hydrodynamic simulations in Chapter 5 with a view to predicting the synchrotron emission from these areas, something that may be detectable with the Square Kilometer Array.
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McCullough, Matthew Philip. "Topics in BSM physics : supersymmetry, dark matter and baryogenesis." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:f2a6c703-8b95-4345-9477-4afeea355a8e.
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Under the umbrella of Theoretical Physics, progress in ‘Beyond the Standard Model’ (BSM) physics proceeds broadly along two main avenues of investigation. The first is concerned with constructing theories that attempt to explain observations, or address theoretical problems, which cannot be explained within the tremendously successful Standard Model (SM) of particle physics. The second involves looking for new ways to observe or test BSM physics, and such tests are usually developed with current experimental hints, or attractive theoretical models, in mind. This thesis contains material which falls under both approaches. Part I is concerned with Supersymmetry (SUSY). We review the basics of SUSY, and the current state of this field, and then present a novel model for SUSY at the TeV scale. This model has a Higgs sector similar to the SM and possesses a continuous U(1)R symmetry, dramatically suppressing contributions to flavour-changing neutral currents, which can be problematic in SUSY models. After this we demonstrate that if more than one SUSY-breaking sector is present then this could lead to a rich spectrum of states with mass roughly twice the gravitino mass. In particular, if SUSY-breaking in a hidden sector arises dynamically then multiple ‘Goldstini’ and ‘Modulini’ states can arise, which couple to visible sector fields via the ‘Goldstino Portal’. We also demonstrate a new phenomenon which can occur in the context of multiple hidden sectors. If one sector breaks SUSY then this can ‘stimulate’ other sectors into also breaking SUSY, even if they are incapable of doing so on their own. Part II focusses on the matter in our Universe. We review our current understand- ing of how the visible matter in our Universe came into existence, and our current understanding of the nature of dark matter (DM). Following this we describe how DM could potentially be indirectly observed through its effects on cold white dwarf stars. Alternatively, if DM were detected by independent means, then observed cold white dwarfs could be used to place limits on the DM density in globular clusters, giving clues as to how these clusters of stars formed. We then present a new model for the co-generation of both the visible and dark matter in our Universe. This proceeds by generating a particle anti-particle asymmetry in the dark sector, which is then shared with the visible sector. This model predicts the existence of a light, m ≲ 5 eV, scalar particle which derivatively couples to DM, and provides a final state for the symmetric DM component to annihilate away into. Work completed during the period of this D.Phil is contained in [1–8], however only material in [3–6, 8] is presented in this thesis.
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Laycock, Thomas Daniel. "Dark matter excitations via massive vector bosons." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21959.
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A model of dark matter excitations is studied in an attempt to explain the anomalously large 511 keV photon line emission observed by the SPI spectrograph on INTEGRAL to be originating from the galactic bulge of the Milky Way. The proposed dark matter WIMP has a near degenerate mass partner a few MeV heavier. Scattering between dark matter particles leads to excitations, with the subsequent decays producing an electron-positron pair. In this way, the kinetic energy of the massive dark matter particles can be efficiently converted into electron-positron pairs moving slow enough to produce the narrow annihilation line observed. With a sufficiently large mass gap, kinematic considerations and the cuspy dark matter density profile constrain excitations to the galactic bulge where the escape velocity, and thus the fraction of dark matter particles above the kinematic cutoff, is large.Un model d'excitations matière sombre est etudié dans une tentative d'explication de la ligne d'emission anormalement large observé par le spectrographe SPI sur INTEGRAL originaire du bulbe galactique de la Voie Lactée. La matière sombre WIMP proposée possède un partenaire ayant une masse de quelques MeV supplémentaires. La diffusion entre les particules de matière sombre mène aux excitations et à la désintégration ultérieure en une paire électron-positron. De cette façon, l'énergie cinétique des particules de matière sombre peut être convertie en paires électron-positron se déplaçant suffisement lentement pour produire l'étroite ligne d'annihilation observée. Avec un espacement en masse suffisement grand, les considérations cinématique et un profil de densité de la matière sombre cuspy contraignent les excitations au bulbe galactique, où la vitesse d'échappement, et donc la fraction de particules matière sombre au-dessus du seuil cinétique, est grande.
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Marchese, J. T. "Background studies for the CRESST dark matter search." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365695.
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Barton, David Alan. "Particle Discrimination Using a High-Pressure Xenon Gas Scintillation Detector." Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/179369.
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PhysicsPh.D.
This work presents results on the study of the scintillation of high-pressure Xenon gas irradiated by various sources. Noble gases such as Xenon give off characteristic scintillation light when irradiated. The goal of the study was to develop a characteristic based on the scintillation time response of Xenon gas that would reliably discriminate between events from different types of primary radiation (neutron or gamma). A reliable discrimination characteristic would enable the development of room temperature, gas phase detectors for use in the search for Galactic Dark Matter. The surprising result of the present work was that a reliable discrimination characteristic existed for distinguishing x-ray, gamma ray, and alpha particle events. Results for neutrons were negative. This was due to several factors: Ionization tracks in xenon generally form two roughly cylindrical regions. A region near the center of the track, called the core, has very dense ionization. An outer region, called the penumbra, has sparse ionization. In Xenon, recombination of ions and the subsequent scintillation from the penumbra region happens slowly and can be easily distinguished from scintillation that happens in the core region. Nuclear recoils resulting from neutron collisions that give recoil energies in the same range as that predicted for WIMP-nuclear collisions are of such low energy that they do not produce a significant penumbra region in Xenon gas. As such, the scintillation time response for these events is similar to that of high-energy gamma rays. Other results of the present work include: The amount of energy deposited in the gas needed to produce a scintillation photon was measured for gamma rays and was found to be in agreement with results from other experiments. Low-energy gamma rays appeared to produce more scintillation photons for an equal amount of energy deposited than high-energy gamma rays. The decay of the singlet and triplet molecular states of xenon was observed and the lifetimes of these states were measured. The singlet state lifetime was found to be independent of pressure while the triplet state lifetime was dependent on pressure. The lifetimes were measured and compared to previous results. A better understanding of the ionization, recombination, and scintillation processes of gaseous Xenon was achieved. Argon gas has been proposed as an alternative to Xenon gas for use in a high-pressure gas scintillation detector due to its lower mass and its property of forming a core ionization region that is much less dense than the core region of xenon. This substitution may allow for a reliable discrimination characteristic to be developed.
Temple University--Theses
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Panci, Tibaldo. "Dark matter phenomenology." Paris 7, 2011. http://www.theses.fr/2011PA077061.
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Dans cette thèse j'essaye de résumer la phénoménologie de la Matière Noire (MN) dans tous ses aspects: Détection Directe, Indirecte et constructions de modèles. Il s'agit d'un domaine très prometteur, car la profusion de mesures de ces dernières années l'a rapidement fait progresser et l'a rendu très dynamique. En ce qui concerne la Détection Directe je passe en revue les principaux ingrédients et recettes pour le calcul des signaux dus à une diffusion WIMP-noyau. Je présente le traitement analytique permettant de calculer le taux théorique attendu. Avec un choix standard des caractéristiques du halo de MN et de la section efficace d'interaction, je présente les régions favorisées actuelles et les contraintes sur la MN. En ce qui concerne la Détection Indirecte, je fournis les ingrédients les plus avancés pour calculer les signaux d'annihilations et désintégrations de MN à l'échelle du TeV. Avec ces ingrédients et recettes, je calcule les contraintes sur la MN qui sont imposées par le fond diffus gamma. Je considère les données de FERMI (1ere année) et je les compare aux prédictions d'annihilation et désintégration de MN. Enfin, comme les annihilations de MN après recombinaison et pendant l'époque de la formation des structures déposent de l'énergie dans le milieu intergalactique primordial, j’enquête également sur les contraintes imposées par la profondeur optique observée de l'Univers. En ce qui concerne la construction de modèles, je présente deux modèles jouets de MN qui peuvent échapper aux contraintes actuelles de détection directe. Ils sont fondés sur l'hypothèse que les forces entre les deux secteurs pourraient ne pas être à courte portéeIn this Ph. D. Thesis I have tried to summarize the Dark Matter (DM) phenomenology in ail aspects: Direct Detection, Indirect Detection and some aspects of mode! building. This is a very promising area as the profusion of ground and satellite-based measurements in recent years has rapidly advanced the field making it dynamic and timely. Concerning DM direct detection I review the main ingredients and recipes for Computing signals due to a WIMP-nucleus scattering I present the analytic treatment that allows us to derive the theoretical rate expected and, considering a standard choice in the features of the DM Halo and interaction cross section (point-like interaction), I report the current fits and constraints on DM properties. Concerning DM indirect detection, I provide the most advanced ingredients and recipes for Computing signals of TeV-scale DM annihilations and decays. Subsequently considering these ingredients and recipes, I compute the gamma ray constraints on DM properties that are imposed by the observed diffuse gamma rays. ] consider the data from FERMI first year observations and I compare them to the gamma rays fluxes predicted by DM annihilation and decays. Finally, as DM annihilations after recombination and during the epoch of structure formation deposit energy in the primordial intergalactic medium, I also investigate the constraints that are imposed by the observed optical depth of the Universe. Concerning model building, I present two DM toy mode 1s that can evade the current constraints on direct detection searches. They are based on the assumption that the forces between the two sectors might not be short range
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Whittamore, Zakary. "Isospin-violating dark matter and direct detection experiments." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123143.
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Hints of direct detection of dark matter have been presented by the DAMA, CoGeNT, and CRESST collaborations, despite a number of null results that seem to contradict such claims. Although standard spin-independent dark matter is not capable of reconciling the results, dark matter models containing isospin-violating couplings have shown promise in solving the issues surrounding direct detection of dark matter. Inelastic or momentum-dependent scattering dark matter has also been shown to help alleviate these tensions. In light of the 2012 XENON100 observations, updated analysis of surface event contamination at CoGeNT, revision of the energy resolution employed by XENON10, and new results from the CDMS-II silicon detectors, we study the extent to which spin-independent, spin-dependent, and combined models of isospin-violating dark matter are capable of explaining current direct detection data. Moreover, we explore the effect of an energy-dependent sodium quenching factor $Q_{\rm Na}$ for fitting the DAMA observations, and give an isospin-violating prediction for XENON1T. In addition to the usual analysis involving phase space plots, we investigate a halo-independent model of dark matter in the space of minimum velocities required for a dark matter particle to scatter off a given nucleus. For the first time, such an analysis is performed for models of dark matter which embrace both inelastic and isospin-violating couplings, as well as for dark matter with momentum- and spin dependent interactions. With respect to the models considered herein, our results do not support a dark matter interpretation of direct detection data in either the standard or halo-independent formalisms.Conseils de détection directe de la matière noire ont été présentés par les DAMA, CoGeNT, et CRESST collaborations, malgré un certain nombre de résultats nuls qui semblent contredire ces allégations. Bien que la norme matière noire indépendante du spin n'est pas capable de concilier la résultats, la matière noire modèles contenant couplages de isospin-violation ont montré des résultats prometteurs dans résolution des problèmes de détection directe de la matière noire. Diffusion inélastique ou dynamique dépendant de la matière noire a également été démontré que aider à atténuer ces tensions. À la lumière des observations XENON100 2012, analyse actualisée de la contamination de l' événement de surface à CoGeNT, la révision de la résolution de l'énergie utilisée par XENON10, et de nouveaux résultats provenant des détecteurs de silicium CDMS-II, nous étudier la mesure dans laquelle indépendante du spin, dépendant du spin, et des modèles combinés de la matière noire isospin-violation sont capables d'expliquer les données de détection directs actuels. De plus, nous explorons l'effet d'une trempe de sodium dépendant de l'énergie facteur $Q_{\rm Na}$ pour le montage des observations DAMA, et de donner une prévision de isospin-violation de XENON1T. En plus de l'analyse habituelle impliquant des parcelles de l'espace de phase, nous étudions un modèle de halo-indépendant de la matière noire dans l'espace des vitesses minimales requises pour une particule de matière noire se disperser hors d'un noyau donné. Pour la première fois, une telle analyse est effectuée pour les modèles de matière noire qui embrassent les deux couplages élastiques et isospin-violation, ainsi que de la matière noire avec des interactions dépendant du dynamique et spin. En ce qui concerne les modèles considérés ici, nos résultats ne soutiennent pas une question d'interprétation sombre de données de détection directe soit dans la norme ou formalismes halo-indépendant.
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Yakovleva, Elizaveta. "Dark Photon decay generated by muons in the SHiP experiment." Thesis, Uppsala universitet, Institutionen för materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414520.
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This project has investigated the muon background of the SHiP experiment to determine whether it can boost the experiment sensitivity to visible Dark Photon decay. Using Fermi-Weizsäcker-Williams approximation to muon scattering we found the probability of muons generating massive photons, using Bremsstrahlung and direct lepton pair production as an estimation of the frequency of muon EM-interactions. In this work we only considered muons with momenta above 10 GeV/c. The number of visible Dark Photon decays was calculated for a range of the coupling constant and photon mass. The resulting range that promised visible decay has already been excluded by previous experiments, but the method could be used to further investigate enhanced production of Dark Photons from muons and electrons, and possibly also production of Axion-like particles. The work could also be used to estimate sensitivities of other experiments using muons.
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Danninger, Matthias. "Searches for Dark Matter with IceCube and DeepCore : New constraints on theories predicting dark matter particles." Doctoral thesis, Stockholms universitet, Fysikum, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89820.
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The cubic-kilometer sized IceCube neutrino observatory, constructed in the glacial ice at the South Pole, searches indirectly for dark matter via neutrinos from dark matter self-annihilations. It has a high discovery potential through striking signatures. This thesis presents searches for dark matter annihilations in the center of the Sun using experimental data collected with IceCube. The main physics analysis described here was performed for dark matter in the form of weakly interacting massive particles (WIMPs) with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore sub-array was included in the analysis, lowering the energy threshold and extending the search to the austral summer. Data from 317 days live-time are consistent with the expected background from atmospheric muons and neutrinos. Upper limits were set on the dark matter annihilation rate, with conversions to limits on the WIMP-proton scattering cross section, which initiates the WIMP capture process in the Sun.These are the most stringent spin-dependent WIMP-proton cross-sections limits to date above 35 GeV for most WIMP models. In addition, a formalism for quickly and directly comparing event-level IceCube data with arbitrary annihilation spectra in detailed model scans, considering not only total event counts but also event directions and energy estimators, is presented. Two analyses were made that show an application of this formalism to both model exclusion and parameter estimation in models of supersymmetry. An analysis was also conducted that extended for the first time indirect dark matter searches with neutrinos using IceCube data, to an alternative dark matter candidate, Kaluza-Klein particles, arising from theories with extra space-time dimensions. The methods developed for the solar dark matter search were applied to look for neutrino emission during a flare of the Crab Nebula in 2010.
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Johnson, Evan Wesley. "Resonant Interactions of Dark Matter Particles Using Effective Field Theory." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563412934740044.
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Lacroix, Thomas. "Phenomenology of dark matter particles at the centers of galaxies." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066060/document.
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Élucider le mystère de la matière noire est l’un des plus grands défis de la physique moderne, à l’interface entre l’astrophysique, la cosmologie et la physique des particules. Dans cette thèse, j’aborde différents aspects de la recherche indirecte des particules de matière noire, approche complémentaire à la détection directe et à la production dans des collisionneurs. Nous entrons dans une nouvelle ère grâce à des instruments remarquables et c’était donc le moment opportun pour s’attaquer au problème du profil de densité de matière noire au centre des galaxies par des méthodes originales. C'est la motivation principale de ma thèse. Dans ce travail, je tire parti des avancées technologiques afin d’explorer de nouvelles façons d’étudier la région centrale des halos de matière noire. Je me concentre en particulier sur les pics de matière noire, qui correspondent à des augmentations extrêmement fortes de la densité de matière noire pouvant être induites par les trous noirs supermassifs. Je montre qu’il est possible d’aller au-delà des recherches standards en étudiant les photons émis par des électrons et positrons produits dans les processus d’annihilation des particules de matière noire. Dans ce contexte, je décris une nouvelle technique pour modéliser la propagation des rayons cosmiques pour des profils d'injection très piqués. Je développe des modèles originaux de l’émission diffuse dans les régions centrales des galaxies, pour la Voie Lactée mais également pour d’autres galaxies, ce qui permet d’expliquer certaines observations récentes et de faire des prédictions pour des observations futuresUnveiling the nature of dark matter is one of the greatest challenges of modern physics, at the interface between astrophysics, cosmology and particle physics. In this thesis, I tackle various aspects of indirect searches for dark matter particles, which provide a complementary approach to direct detection or collider experiments. We are now entering into an era of instruments with outstanding capabilities, so it was timely to tackle the problem of the dark matter density profile at the centers of galaxies with novel methods, which motivated this thesis. Taking advantage of these technological advances, I investigate new ways of probing the very central part of dark matter halos, especially focusing on dark matter spikes, i.e. very strong enhancements of the dark matter density that can form around supermassive black holes. I show that we can go beyond standard dark matter searches by studying photon emission from electrons and positrons produced in dark matter annihilation processes. In this context, I describe a new cosmic-ray propagation technique to account for injection by spiky distributions at the centers of galaxies. I develop novel models of the diffuse emission in the central regions of galaxies, focusing not only on the center of the Milky Way, but on the central regions of other galaxies as well. This allows me to explain recently reported observations and make predictions for future observations
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Wang, Chao. "A model study of the dynamics of dark energy." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106572.
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Observational facts indicate that the expansion of the universe is accelerating, rather than decelerating, because 73% of the total energy density of the universe is a "dark energy" with strong negative pressure, ω < −1/3. In this thesis, we introduce a dynamical dark energy model with dilatational symmetry, which contains two scalar fields coupled to gravity. Because of the dilatational symmetry, there is no cosmological constant Λ in the Lagrangian, and, instead, two scalar fields generate the dark energy, evolving slowly in time. At early times, the system is in the slow roll regime, corresponding to Higgs inflation due to the Higgs field. At late times, the dynamical dark energy dominates the universe and eventually behaves just like the cosmological constant, and the universe becomes exponentially expanding with the scale factor a(t) ∝ exp{Ht}. The numerical results from solving the dynamic equations of the system agree well with the observational facts, which indicates that our model gives a good description of the universe. At the end of the thesis, we consider the one-loop corrections to our model, and show that they do not alter the classical results in any significant way.Les observations actuelles de l'expansion de l'univers indiquent une accéleration decette expansion due à 'l'énergie sombre', qui compte pour 73% de la densité d'énergie totalle de l'univers et qui se comporte comme un fluide avec une pression négative, ω < −1/3. Cette thèse présente un modèle dynamique d'énergie sombre invariant sous une symétrie de dilatation comprenant deux champs scalaires couplés à la gravitation. La constante cosmologique n'est pas présente dans ce modèle, de par la symétrie de dilatation; les champs scalaires génèrent une énergie sombre évoluant dans le temps. Dans l'univers primordial, le système se situe dans le régime d'évolution lente correspondant à l'inflation cosmolgique due au champ de Higgs. L'énergie sombre dynamique agit ultérieurement sur l'évolution de l'univers comme une constante cosmologique; le facteur d'échelle de l'univers accroit de manière exponentielle a(t) ∝ eHt. Les simulations numériques concordent très bien avec les observations actuelles. Les perturbations quantiques de premier ordre sont ensuite calculées, et justifient la validité des résultats obtenus de manière classique.
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Vincent, Aaron. "Cosmic ray anomalies and positrons from the dark side." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110551.
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This thesis examines two recent anomalous cosmic ray (CR) positron detections in the context of the ongoing search for the particle nature of dark matter (DM), which composes 85% of the matter content of the Universe. The first CR anomaly, detected by the European INTEGRAL/SPI experiment via 511 keV gamma rays from the center of the Galaxy, suggests an unaccounted-for production of low-energy positrons in the region surrounding the galactic center (GC). We model the production of electron-positron pairs from the decay or interaction of cold dark matter in an Einasto profile. We show that the INTEGRAL signal can be fit by scattering DM in a halo with the shape parameters predicted by many-body simulations, with a significance on par with previous phenomenological fits, but with six fewer degrees of freedom. This can be achieved with annihilating low-mass DM, or with scattering of excited dark matter (XDM), with cross-sections compatible with thermal WIMP production in the early universe.The second CR anomaly is the rising positron fraction from 10 to 200 GeV observed by the PAMELA satellite and confirmed by NASA's Fermi-LAT. Although previous studies had considered Sommerfeld-enhanced DM annihilation as a possible source, they did not consider the full impact of the dark matter substructure predicted to exist by simulations. We show that including this substructure can give a better fit to the PAMELA and Fermi data, but that this is not sufficient to overcome the strict gamma-ray bounds from the Fermi-Large Area Telescope (LAT) diffuse gamma ray data. We finally show that a single, nearby subhalo can explain the excess, while simultaneously avoiding gamma ray and dipole anisotropy constraints, and that it is possible to create a Sommerfeld-enhanced particle physics model that produces the required annihilation cross-section and is compatible with cosmological bounds.Nous examinons dans cette thèse deux détections récentes de positrons dans le rayonnement cosmique, dans le contexte d'une origine possible sous la forme de matière sombre (MS). Quoique celle-ci englobe 85% de la matière dans l'univers, sa détection jusqu'à présent ne s'est faite que par son intéraction gravitationnelle. La première anomalie, observée par le satellite Européen INTEGRAL via un excès de rayons gamma de 511 keV issus du centre de la Voie Lactée, suggère une production élevée de positrons dans cette région. En modélisant la production de paires d'électrons-positrons par la décomposition ou l'intéraction de MS dans un profil Einasto, nous obtenons un ajustement d'aussi bonne qualité que les meilleures études précedentes purement phénoménologiques, mais avec six degrés de liberté en moins. Ceci peut être réalisé avec l'annihilation de MS d'environ 1 MeV, ou avec la diffusion de MS à plusieurs niveaux d'énergie (XDM) de masse élevée, avec des sections efficaces consistantes avec la production thermique de WIMPs au début de l'Univers. La deuxième anomalie, mesurée par le satellite PAMELA et confirmée par le Large Area Telescope (LAT) de Fermi, est constituée d'une fraction de positrons qui s'élève de 10 à 200GeV et qui ne peut être expliquée par le spectre d'antimatière secondaire attendu. Quoique des études précédentes ont considéré une explication en terme de MS qui s'annihile à l'aide d'un mécanisme de Sommerfeld, nous avons été les premiers à examiner l'impact des milliers de subhalos (SH) de MS qui devraient exister selon les simulations numériques. Nous démontrons que l'inclusion des SH donne un meilleur ajustement aux données de PAMELA et Fermi, mais que ce n'est pas suffisant pour obéir aux limites établies par les observations gamma de Fermi-LAT. Nous montrons finalement qu'un seul SH très proche pourrait expliquer l'anomalie PAMELA, sans enfreindre les contraintes de rayonnement gamma et d'anisotropie dipolaire actuelles et qu'il est possible de créer un modèle de physique des particules qui produit la section efficace nécéssaire et qui est toutefois consistante avec les limites établies par la cosmologie.
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Heurtier, Lucien. "Particle physics and Cosmology beyond the Standard Model : Inflation, Dark Matter and Flavour." Palaiseau, Ecole polytechnique, 2015. https://theses.hal.science/tel-01176578/document.
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Cette thèse se concentre sur l’étude des aspects de la physique au delà du modèle standard et de ses applications à la cosmologie. Depuis les temps reculés de l’évolution de l’Univers, jusqu’à la supersymétrie de basse énergie et à la phénoménologie des accélérateurs, des travaux variés ont été réalisés utilisant pour la majeure partie une formulation de basse énergie, et ce à des stades différents de l’Histoire de l’Univers. En effet, des modèles d’inflation sont présentés sous l’angle de théories effectives (à un champs) provenant de théories de hautes énergies issues de la supergravité et de la théorie des cordes. De plus, des modèles de matière noire incluant la présence d’une particule médiatrice sont étudiés à l’aide d’opérateurs effectifs de dimensions supérieures, générés explicitement à partir d’une théorie microscopique sous-jacente. De tels modèles semblent expliquer de récentes mesures du spectre de rayons X mesuré dans certains cluster de galaxies. Enfin l’étude des changements de saveurs dans l’extension supersymétrique incluant des jauginos de Dirac du modèle standard prédit des signatures expérimentales qui seront très probablement recherchées lors des prochaines acquisitions du LHCThis thesis has been focusing on beyond the Standard Model aspects of particle physics and their implication in cosmology. From the early times of the universe evolution, to current low energy supersymmetry and colliders phenomenology, various works have been achieved using mostly an effective, low energy formulation, at several different periods of the Universe History. Namely, models of Inflation are presented as effective single field theories arising from supergravity, string inspired UV completion models. Furthermore, models of dark matter including a mediator particle are studied with the use of effective higher dimensional operators that are generated explicitly from microscopic underlying theories. Such models were able to produce interesting results for explaining recent measurements on the X-rays spectrum of galaxy clusters. Finally, the study of flavour changing processes in the Dirac gaugino supersymmetric extensions of the Standard Model was explored in details, predicting some challenging signatures that are to be searched for at the next run of the LHC
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Harvey, David Richard. "Measuring the self-interaction cross-section of dark matter with astronomical particle colliders." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/10447.
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The dark matter paradigm has been a great source of speculation in both the 20th and 21st Centuries. Since its proposed existence in 1933, the mounting evidence has led to this theoretical particle becoming one of the greatest mysteries of modern physics. However, despite its dominant presence in the Universe, little is known about its nature and how it behaves. In this thesis I critically analyse one particular property of dark matter: the self-coupling. The self-interacting dark matter paradigm hypothesises that dark matter is not collisionless as assumed in most cosmological simulations, and in-fact has some probability that it will scatter off itself. Such a self-coupling will resolve many discrepancies that exist between observations and theory, particularly on small, non-linear scales. Moreover, any detection of a self-interaction cross-section will place considerable limitations on the acceptable particle physics models of dark matter and hence has grown to become an important question. In this thesis I develop and implement a method to constrain the self-interaction cross-section of dark matter that exploits continually accreting and merging groups of galaxies as they fall into galaxy clusters. Utilising the ubiquitous nature of accreting substructure, I measure the offsets between dark matter and baryonic gas as they become separated due to their differing interaction properties. Studying this effect over a sample of events, I will be able to make the first ever statistical estimate of the cross-section of dark matter, while averaging over many different unknown merging scenarios. I begin my thesis by deriving an analytical description of sub-halo in-fall, allowing me to constrain dark matter self-interaction models directly from observations. In this study, I find that current archival data should be able to detect a difference in the dynamical behaviour of dark matter and standard model particles at 6σ, and measure the total interaction cross-section σDM/m with 68% confidence limits of ±1 cm2g-1. Having constructed a new method to derive constraints on the cross-section of dark matter I carry out a study into the potential systematics that may affect a measurement. I determine the accuracy of weak gravitational lensing, which is the distortion of light due to intervening mass, as a tool to estimate the positions of substructure in galaxy clusters. I find that the public Lenstool software can measure the position of individual 1:5 x 1013Mʘ peaks with ~ 0:3" systematic bias, as long as they are at least ~ 30" from the cluster centre. Finally, I develop a pipeline that can analyse a sample of inhomogeneous observations from The Hubble Space Telescope and the Chandra X-ray Observatory. By measuring the positions of dark matter, gas and galaxies for 68 individual merging events, from a total of 28 galaxy clusters, I detect a 7:4σ offset between gas and an unobserved dark mass. I make the first ever measurement of cross-section of dark matter from a sample of clusters finding σDM < 0:50cm2/g [95% CL], the best constraints to date. In addition to this I find that the brightest group galaxy in-fact tends to lead the dark matter halo during merging events. Although evidence for the existence of interacting dark matter, I conclude that the astrophysics of the BCG is complicated, and that this apparent directional bias should be considered in all galaxy cluster analyses. Moreover, I show that this technique is easily extendable for future surveys that have larger samples of galaxy clusters, with constraints of σDM < 0:001cm2/g potentially attainable.
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Bailey, Catherine N. "The Cryogenic Dark Matter Search: First 5-Tower Data and Improved Understanding of Ionization Collection." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1252692321.
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Thesis(Ph.D.)--Case Western Reserve University, 2010Title from PDF (viewed on 2009-12-30) Department of Physics Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Coulter, Philip. "Cryogenic phonon-scintillation detectors with NTD germanium readout." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:8ee65ffd-1f0f-4318-894f-c82746acaefb.
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Cryogenic detectors are an advanced technology for both dark matter and neutrinoless double beta decay searches, having the key advantage of a range of possible absorber materials that can be used for the detectors. Neutron transmutation doped germanium sensors are highly sensitive thermometers ideal for use at milli kelvin temperatures, with a simple repeatable resistance temperature relation. To discriminate between candidate events and background events simultaneous measurements can be made of the energy deposited in the detector as phonons and the energy emitted by the absorber crystal as scintillation light. Phonon detectors with a calcium tungstate or calcium molybdate crystal as the target and an NTD sensor as a thermometer were made in Oxford, along with a light detector with a light-absorbing silicon layer on a sapphire crystal, also with an NTD thermometer. A system of electronics was designed and tested in Oxford to bias and readout the NTD thermometers, while the setup inside the cryostat was developed to provide a thermally and mechanically stable shielded environment for the detectors. As part of this, prototype semi-rigid kapton cabling for use in the EDELWEISS experiment was installed and tested in the cryostat. Three different NTD germanium sensor types were characterized and calibrated in the cryostat and two of these selected for use on the phonon and light detectors. The detectors were operated at temperatures as low as 9 mK and tested with radioactive sources to produce energy spectra. Baseline resolutions of 1.7 keV and 2.5 keV, respectively, were achieved for the calcium molybdate and calcium tungstate phonon detectors. A working scintillation light detector was demonstrated as part of a phonon-scintillation detector module with a suggested application in double-beta decay searches.
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Day, Francesca. "Astrophysical signatures of axion-like particles." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:215f6432-6dbb-4a16-80d8-3ad0bc76ec2d.
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The Standard Model of particle physics has enjoyed unprecedented success in predicting experimental results. However, evidence from astrophysical observations points to the existence of a dark sector of particles that interact only very weakly with the Standard Model. In this work, we search for dark sector signatures in X-ray telescope data. Much of this work concerns a class of hypothetical particles, the axion-like particle (ALP). ALPs are a theoretically well-motivated extension of the Standard Model. If ALPs exist, they may lead to intriguing astrophysical signatures: in the presence of a background magnetic field, ALPs and photons can interconvert. We could detect ALPs by searching for photon to ALP conversion. For example, photons produced by point sources in or behind galaxy clusters may convert to ALPs in the cluster's magnetic field. This could lead to observable spectral anomalies. Using this strategy, we place world leading bounds on the ALP-photon coupling. One potential signal of dark matter is an anomalous line in the spectra of galaxies and galaxy clusters. In 2014, an anomalous line was found at an energy of 3.5 keV. The nature and cause of this line is still under discussion. We analyse a scenario in which the 3.5 keV line arises from dark matter decay to ALPs, which interconvert with 3.5 keV photons in astrophysical magnetic fields. We further report an anomalous deficit at 3.5 keV in the spectrum of the Active Galactic Nucleus at the centre of the Perseus galaxy cluster. This motivates the study of a new model in which both features are caused by âfluorescent dark matterâ which resonantly interacts with 3.5 keV photons. We analyse observations of Perseus at 3.5 keV to date, and show that they are well explained by this model. Further theoretical and experimental work is needed to discover or exclude fundamental physics effects in X-ray spectra.
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McGowan, Richard. "Data analysis and results of the upgraded CRESST dark matter search." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:c5299add-8aa2-4633-9fd6-3ab05ec84e89.
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CRESST has an established analysis procedure to evaluate the energy of the events it detects, in an attempt to detect WIMP dark matter. It was shown that unless eight classes of contaminant event were removed prior to this analysis, the output energy spectrum would be significantly biased. For both scientific and practical reasons, the removal process should be blind, and a series of cuts were developed to flag these events automatically, without removing any true events. An event simulation package was developed to optimise these cuts. It was shown that noise fluctuations could also reduce CRESST’s sensitivity, so a noise-dependent acceptance region was introduced to resolve this. The upgraded CRESST experiment included a new electronics system to provide heating and bias currents for 66 detectors. This system was integrated into the CRESST set-up, and it was shown that the electronics contributed no extra noise to the detectors. Data with an exposure of 50 kg days were analysed using the cuts and the noise-dependent acceptance. The cuts were successful, with no contaminant event retained and a live time reduction of just 2.3%. The data were used to set an upper limit on the WIMP-nucleon cross section for elastic scattering with a minimum of 6.3 × 10^(−7) pb at a WIMP mass of 61 GeV. This is a factor of 2.5 better than the previous best CRESST limit.
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Giacchino, Federica. "A Dark Matter through the Vector-like Portal." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/258213.
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Although about a century has passed since its discovery, and despite the scientific and technological progress of our society has gone through, the nature of the Dark Matter (DM) is a mystery not yet solved. It is a big challenge for the scientific community, its identification would mean the understanding of what seemingly makes up 84% of the matter content in the Universe. We say “seemingly” because so far all evidences for DM are purely gravitational. This implies that what we call dark matter could be either a manifestation of our incomplete understanding of gravity on large scales, or a new form of matter, in particular a new kind of elementary particle. Among the plethora of possible DM candidates, this work will consider the Weakly Interactive Massive Particle (WIMP). Up to know the observed value for the relic abundance is the only solid parameter which we can count on, and the WIMP is the candidate that, through a fashionable mechanism of production, gives a result for the relic abundance in agreement with the cosmological observations. In order to demonstrate that this is indeed the valid explanation to the DM problem, a non-gravitational signal and also a model to interpret a possible Dark Matter message are needed. This may be expressed in various ways, and our approach is based on so-called simplified model. We have built a new t-channel simplified model which promotes a real scalar particle as DM and a vector-like fermion as mediator, dubbed the Vector-like Portal. In our framework, there are very few free parameters, the DM mass, the mass of the mediator and at least one Yukawa coupling. We have discovered an intriguing feature in the annihilation cross-section, a d-wave suppression in the limit of light final state fermions (compared to the DM mass). This seemingly innocuous observation will turn out to be crucial both for thermal freeze-out and for indirect searches for DM, for which higher order effects become relevant. In particular, we have performed a comprehensive analysis of the impact of next-to-leading order corrections to the annihilation cross-section, including coannihilation, as well as on elastic scattering processes. We have exploited the complementarity of direct, indirect and collider searches to set constraints on the parameter space of some simple vector-like portal scenarios, including coupling to Standard Model leptons, light quarks and the top quark. In addition, we have studied the phenomenological consequences of electroweak corrections and the detectability ofour candidate.Bien que presque un siècle ait passé depuis sa découverte, et malgré les progrès scientifiques et technologiques de notre société, la nature de la matière noire (MN) est un mystère irrésolu. C’est un grand challenge pour la communauté scientique, car sa découverte signifierait la compréhension de ce qui semble constituer 80 % du contenu en matière de l’univers. Nous disons “semble” car jusqu’à présent toutes les évidences de MN sont purement gravitationnelles. Cela implique que ce que nous appelons matière noire pourrait être soit une manifestation de notre compréhension incomplète de la gravité à grandes échelles, soit une nouvelle forme de matière, en particulier un nouveau type de particule élémentaire. Parmi la pléthore de candidats de MN possibles, ce travail considèrera la Weakly Interactive Massive Particle (WIMP). A ce jour, la valeur observée de l’abondance relique est le seul paramètre solide sur lequel nous pouvons compter, et la WIMP est le candidat qui, par un élégant mécanisme de production, donne un résultat pour l’abondance relique en accord avec les observations cosmologiques. Pour démontrer que cela est en effet l’explication valide du problème de la MN, un signal non gravitationnel ainsi qu’un modèle pour interpréter un possible message de MN sont requis. Cela peut s’exprimer de plusieurs façons, et notre approche est basée sur les modèles dits simplifiés. Nous avons construit un nouveau modèle simplifié avec le canal t qui promeut une particule scalaire réel comme MN et un fermion de type vector-like comme médiateur, et communément appelé le portail vector-like. Dans notre cadre, il y a très peu de paramètres libres, la masse de la MN, la masse du médiateur et au moins un couplage de Yukawa. Nous avons découvert une caractéristique intrigante dans la section efficace d’annihilation, une suppression de type d-wave dans la limite de fermions légers dans l’état final (en comparaison avec la masse de la MN). Il se trouve que cette observation, qui semble anodine au premier abord, est cruciale pour le freeze-out et pour les recherches indirectes de MN, pour lesquelles les effets aux ordres supérieurs deviennent relevants. En particulier, nous avons réalisé une analyse compréhensive de l’impact des corrections après l’ordre dominant de la section efficace d’annihilation, ainsi que des processus de diffusion élastique. Nous avons exploité la complémentarité des recherches directes, indirectes et aux collisionneurs afin de contraindre l’espace des paramètres de quelques scénarios simples de portails vector-like, dont le couplage au leptons du Modèle Standard et au quark top. De plus, nous avons étudié les conséquences phénoménologiques des corrections électrofaibles, et la détectabilité de notre candidat.
Option Physique du Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Neveu, Jeremy. "Contraintes expérimentales sur des modèles à champ scalaire léger en cosmologie et physique des particules (expériences SNLS et CMS)." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066233/document.
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Face à la nature inconnue de l'énergie noire et de la matière noire, des modèles à champ scalaire léger ont été proposés pour expliquer l'accélération tardive de l'expansion de l'Univers et l'apparente abondance de matière non baryonique dans l'Univers. Dans une première partie, cette thèse confronte de la façon la plus précise possible les données de cosmologie les plus récentes au modèle du Galiléon, une théorie de gravité modifiée possédant des propriétés théoriques particulièrement intéressantes. Des contraintes observationnelles sur les paramètres du modèle sont dérivées en utilisant les dernières mesures liées aux distances cosmologiques et à la croissance des grandes structures de l'Univers. Un bon accord est observé entre les données et les prédictions théoriques, faisant du Galiléon un modèle alternatif compétitif avec celui de la constante cosmologique. Dans une seconde partie, la production de Branons, particules scalaires candidates au statut de matière noire venant d'une théorie de dimensions supplémentaires, est recherchée dans les collisions proton-proton enregistrées en 2012 par l'expérience Compact Muon Solenoid auprès du Grand Collisionneur de Hadrons. Des événements présentant un photon et de l'énergie transverse manquante dans l'état final sont sélectionnés dans les données et comparés aux estimations des bruits de fonds attendus. Aucun excès d'événements n'étant observé, des limites expérimentales sur les paramètres de la théorie du Branon sont calculées. Elles sont les plus contraignantes à ce jour. Cette thèse se conclut par des arguments pour une description unifiée des deux modèles étudiés, dans le cadre des théories de dimensions supplémentairesThe nature of dark energy and dark matter is still unknown today. Light scalar field models have been proposed to explain the late-time accelerated expansion of the Universe and the apparent abundance of non-baryonic matter. In the first part of this thesis, the Galileon theory, a well-posed modified gravity theory preserving the local gravitation thanks to the Vainshtein screening effect, is accurately tested against recent cosmological data. Observational constraints are derived on the model parameters using cosmological distance and growth rate of structure measurements. A good agreement is observed between data and theory predictions. The Galileon theory appears therefore as a promising alternative to the cosmological constant scenario. In the second part, the dark matter question is explored through an extra-dimension theory containing massive and stable scalar fields called Branons. Branon production is searched for in the proton-proton collisions that were collected by the Compact Muon Solenoid experiment in 2012 at the Large Hadron Collider. Events with a single photon and transverse missing energy are selected in this data set and compared to the Standard Model and instrumental background estimates. No signature of new physics is observed, so experimental limits on the Branon model parameters are derived. This thesis concludes with some ideas to reach an unified description of both models in the frame of extra-dimension theories
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Mertsch, Philipp. "Cosmic ray backgrounds for dark matter indirect detection." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:2734b849-4d7a-4266-8538-d3dc6cab6b20.
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The identification of the relic particles which presumably constitute cold dark matter is a key challenge for astroparticle physics. Indirect methods for their detection using high energy astro- physical probes such as cosmic rays have been much discussed. In particular, recent ‘excesses’ in cosmic ray electron and positron fluxes, as well as in microwave sky maps, have been claimed to be due to the annihilation or decay of dark matter. In this thesis, we argue however that these signals are plagued by irreducible astrophysical backgrounds and show how plausible con- ventional physics can mimic the alleged dark matter signals. In chapter 1, we review evidence of, and possible particle candidates for, cold dark matter, as well as our current understanding of galactic cosmic rays and the state-of-the-art in indirect detection. All other chapters contain original work, mainly based on the author’s journal publications. In particular, in chapter 2, we consider the possibility that the rise in the positron fraction observed by the PAMELA satellite is due to the production through (hadronic) cosmic ray spallation and subsequent acceleration of positrons, in the same sources as the primary cosmic rays. We present a new (unpublished) analytical estimate of the range of possible fluctuations in the high energy electron flux due to the discreteness of plausible cosmic ray sources such as supernova remnants. Fitting our result for the total electron-positron flux measured by the Fermi satellite allows us to fix the only free parameter of the model and make an independent prediction for the positron fraction. Our explanation relies on a large number of supernova remnants nearby which are accelerating hadronic cosmic rays. Turning the argument around, we find encouraging prospects for the observation of neutrinos from such sources in km^3-scale detectors such as IceCube. Chapter 3 presents a test of this model by considering similar effects expected for nuclear secondary-to-primary ratios such as B/C. A rise predicted above O(100)GeV/n would be an unique confirmation of our explanation for a rising positron fraction and rule out the dark matter explanation. In chapter 4, we review the assumptions made in the extraction of the `WMAP haze' which has also been claimed to be due to electrons and positrons from dark matter annihilation in the Galactic centre region. We argue that the energy-dependence of their diffusion means that the extraction of the haze through fitting to templates of low frequency diffuse galactic radio emission is unreliable. The systematic effects introduced by this can, under specific circumstances, reproduce the residual, suggesting that the ‘haze’ may be just an artefact of the template subtraction. We present a summary and thoughts about further work in the epilogue.
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Zhang, Xiaohe. "A novel phonon-scintillation cryogenic detector and cabling solution for dark matter direct detection." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:2a313e80-83bc-423d-8dc3-566b23e80f8d.
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The EDELWEISS experiment is one of the dark matter direct detection experiments. It aims to detect WIMP interactions using an array of cryogenic germanium detectors. In the previous EDELWEISS-II phase, the cables and connectors used have been identified as a major source of neutron background in the experiment, which means that further effort aimed at better WIMP-nucleon interaction detection sensitivity requires a new, different cold cabling solution connecting the detectors to the front-end electronics. Motivated by this, a new two-section cold cabling system based on semi-flexible laminated copper and stainless steel cables has been developed for the EDELWEISS- III phase at Oxford. Batches of prototypes have been tested first in a cryostat at Oxford as part of a phonon-scintillation detector module, and then at the LSM underground laboratory in several EDELWEISS-III commissioning runs. Following that, a final set of cabling has been produced and installed in the EDELWEISS-III setup, which is currently conducting a science run aiming to improve its sensitivity reach compared to the previous results. This new cold cabling system has shown similar electrical performance as the previous coaxial cabling when comparing different cold cabling configurations in a commissioning run at LSM. Also, its background contribution is within the EDELWEISS-III requirements, according to radioactivity level tests and Monte Carlo simulations. In addition, the assembled connectors have allowed hundreds of signal tracks to be installed within a few days and the low material and space budget has made the cables compatible with the compact cryostat design. Besides reading out detectors for dark matter detection, prototypes of this cabling solution for a wider application range have also been produced at Oxford. The next generation dark matter direct detection experiments aim to achieve detection sensitivity better by a few orders of magnitude. This requires a target mass at tonne-scale, which converts to thousands of cryogenic detectors. Cryogenic phonon-scintillation detectors used in current dark matter searches can provide excellent performance but they usually require individual tuning and attention, making operation in large-scale experiments difficult. It is also technically challenging to stably produce such detectors in large quantity. Therefore, a scalable, robust novel detector concept for cryogenic phonon- scintillation detectors to be used in future rare event search experiments has been developed in this work. This detector module consists of a phonon detector based on a CaMoO4 scintillating crystal as the target with an attached NTD-Ge sensor as the thermometer, and a light detector based on a low-temperature PMT. To provide the high voltage necessary for PMT operation while ensuring the detector module can be cooled down and that the performance of the phonon detector is unaffected, a high voltage supply system based on a Cockcroft-Walton generator (CWG), a transformer and a small AC input has been designed and tested in the cryostat. The laminated cabling system is chosen for reading out the phonon channel and connecting the CWG and the PMT. A test run has demonstrated that, the high voltage can be provided to the PMT without causing a problem to the detector operation, and it is feasible to operate the low-temperature PMT at a temperature as low as 17 mK. Testing with a cobalt-57 gamma source, the phonon detector and the light detector have achieved resolutions of 1.07 keV and 34.2 keV for the 122.06 keV peak respectively. This is close to the performance of detectors used in the current dark matter direct searches, proving this detector concept can be applied to future large-scale dark matter direct detection experiments and other rare event searches. Using the light channel in this detector setup, the scintillation properties of CaMoO4 has been studied. In this work, the experimental data of its scintillation decay time constant has been extended from the previous 7 K to milli-Kelvin temperatures. The data are interpreted using a three-level model, confirming the existence of a metastable emission level in CaMoO4, and giving various parameters of its emission centre. This suggests that the work related to producing a high voltage supply and demonstrating the excellent performance of a low-temperature PMT could also be attractive to scintillator studies at cryogenic temperatures.
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Bradley, Adam Wade. "LUX Thermosyphon Cryogenics and Radon-Related Backgrounds for the First WIMP Result." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1390314556.
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Elmer, Martin. "Nouvelle physique entre cosmologie et le LHC : axions, neutrinos et Z'." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10178/document.
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Pendant mes trois ans de doctorat j'ai eu le plaisir de travailler sur trois projets très variés ayant un but commun: mieux contraindre certains modèles de nouvelle physique entre cosmolo- gie et le LHC. Le fait que les densités reliques de matière noire et de baryons sont similaires semble indiquer qu'il y a un lien entre les deux. Nous essayons d'expliquer les valeurs observées en reliant un modèle de leptogenèse au miracle des WIMPs, qui produit naturellement la bonne densité relique. Si l'asymétrie baryonique est produit dans des désintégrations hors équilibre à l'échelle électro-faible et si la matière noire est constituée de WIMPs, les deux densités reliques sont con- trôlées par des processus électro-faibles hors équilibre. Je construis un modèle de leptogenèse à l'échelle du TeV en utilisant une extension du type seesaw inverse du modèle standard avec des singlets additionnels. Pour produire suffisamment d'asymétrie baryonique il faut une violation CP ∼ O(1) qui est difficile à obtenir dans mon cadre. Les axions, tout comme les WIMPs sont de bons candidats de matière noire bien motivés. Il serait très utile de pouvoir les distinguer. Sikivie argumente que si des axions sont dans un condensat de Bose-Einstein, alors ils forment des halos galactiques différents des halos de WIMPs. D'après Sikivie ce sont les interactions gravitationnelles qui thermalisent les axions et qui les condensent. La formation d'un condensat nécessite la génération d'entropie qui ne peut pas être fourni par les interactions gravitationnelles au premier ordre. J'étudie la génération d'entropie par les interactions gravitationnelles en estimant une longueur de dissipation dans le fluide d'axions qui vient de la présence d'une pression anisotrope. Je ne peux pas confirmer la thermalisation rapide d'axions causé par leurs interactions gravitationnelles. Des nouveaux bosons de jauges comme le Z' apparaissent dans un grand nombre d'extensions du modèle standard. On les recherche le plus souvent comme une résonance dans le spectre de masse invariante de leurs produits de désintégration. Le Z' doit être produit sur couche de masse dans ces recherches résonantes. Mais la présence d'un Z' peut aussi influencer d'autres observ- ables cinématiques sans être produit directement, ce qu'on peut utiliser dans des recherches non-résonantes. Je compare ces deux types de recherches au LHC et trouve que pour des petits couplages les recherches résonantes sont plus adaptées mais pour de plus grandes masses et couplages les recherches non-résonantes sont plus performantesDuring the three years as a PhD student I had the pleasure to work on three major projects which are united in the goal to better constrain new physics models between cosmology and the LHC. The similar values of dark matter and baryon relic abundances raise the question whether there is a link between them. We attempt to explain the observed values by relating leptogenesis to the WIMP miracle which gives naturally the right relic abundance. If the baryon asymmetry is produced in electroweak-scale-out-of-equilibrium decays and dark matter is made of WIMPs, both relic densities are controlled by electroweak scale interactions going out of equilibrium. We construct a TeV-scale leptogenesis model using an inverse-seesaw extension of the SM with additional singlets. To produce a large enough asymmetry we require CP violation ∼ O(1) which is difficult to achieve in our set-up. Axions as well as WIMPs are well motivated dark matter candidates. It would be very useful to be able to tell them apart. Sikivie argues that if axions are in a Bose-Einstein condensate they could form a different galactic dark matter halo than WIMPs and that gravitational interactions drive axions into a Bose-Einstein condensate. However for the formation of such a condensate entropy generation is needed which leading order gravitational interactions do not provide. We explore the entropy generation of gravitational interactions by estimating a dissipation scale in the axion fluid due to the presence of a anisotropic stress. We cannot confirm a fast gravitational thermalisation rate. New neutral gauge bosons like the Z' are generic extensions of the standard model which appear in many different models. Traditionally these particles are searched for in resonant searches at colliders, i.e. by producing the particles on-shell and looking for a resonance in the invariant mass spectrum of their decay products. However the presence of a Z' can also affect other kinematic observables without being actually produced on-shell, i.e. non-resonant searches. We compare compare resonant and non-resonant searches at the LHC and find that while for small couplings resonant searches are more sensitive, for larger couplings non-resonant searches are more efficient
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Dutra, Maíra. "Origins for dark matter particles : from the "WIMP miracle" to the "FIMP wonder"." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS059/document.
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Cela fait plus de 80 ans que nous avons des preuves qu'environ 26% de la densité d'énergie de l'univers actuel se présente sous la forme de matière noire, qui interagit avec la matière ordinaire strictement par gravitation. Avec les neutrinos massifs, l’existence de particules de matière noire (DM) indique qu’il faut étendre le modèle standard de la physique des particules (SM) pour en tenir compte. Dans cette thèse, nous explorons la relation étroite entre la nature des couplages reliant la DM aux particules du SM et la production de l'abondance de la DM dans l'univers primordial. Nous commençons par examiner la classe la plus prédictive de candidats DM, les particules massives à interaction faible (WIMP). Leurs masses et couplages sont comparables à ceux du SM, et donc les deux secteurs ont déjà été en équilibre thermique, et l'abondance de DM respecte automatiquement les limites cosmologiques -- le "miracle WIMP". Les limites expérimentales actuelles repoussent l'espace paramétrique viable des modèles WIMP vers des limites complexes, rendant nécessaire l'ajout de particules supplémentaires dans le secteur sombre et la vérification plus précise de la condition de découplage. Après avoir considéré le statut phénoménologique d'une gamme significative de modèles pour les WIMP avec des masses dans l'intervalle 10-10⁴ GeV, nous examinons la phénoménologie d'une DM sur l'échelle MeV dans un modèle de portail Z'. En plus de chercher à améliorer la recherche de WIMPs, il convient de considérer le cas dans lequel DM et SM interagissent si faiblement qu’ils n’ont jamais atteint l’équilibre. Les particules massives à interaction faible (FIMP) sont des candidats DM produits à partir du SM dans des processus hors d'équilibre, un mécanisme appelé freeze-in. Nous montrons que si des champs lourds (10¹⁰-10¹⁶ GeV) interviennent dans les interactions DM-SM, le freeze-in est une possibilité naturelle qui fournit la bonne abondance de DM sans qu'il soit nécessaire d'imposer couplages extrêmement petits. Ces champs lourds sont en fait nécessaires dans des scénarios à hautes énergies théoriquement bien motivés tels que le GUT, le see-saw, la leptogénèse et l’inflation -- nous appelons cette coïncidence intéressante la "merveille FIMP". Nous explorons différentes réalisations de cette possibilité, avec des modèles impliquant des moduli, fermions, bosons de jauge et champs de spin-2 comme les médiateurs lourds. Nous montrons enfin dans quels cas la production de DM pendant le reheating après inflation a un impact sur l’espace paramétrique de tels modèlesFor more than eighty years, we face evidence that about 26% of the energy budget of the universe today is in the form of dark matter, whose interaction with ordinary matter is felt only gravitationally. Along with massive neutrinos, the existence of dark matter particles (DM) indicate that we must extend the standard model of particle physics (SM) in order to account for them. In this thesis, we explore the close relationship between the nature of couplings connecting DM to the SM sector and the production of the DM relic density in the Early Universe. We start by considering the most predictive class of DM candidates, the weakly interacting massive particles (WIMPs). Their masses and couplings are comparable to the SM ones, which ensure that both sectors were once in thermal equilibrium and automatically render the DM relic density within the inferred range -- the so-called "WIMP miracle". The current experimental bounds push the viable parameter space of WIMP models to complex corners, making necessary to add extra particles in the dark sector and to check the decoupling condition more carefully. After reviewing the phenomenological status of a comprehensive spectrum of models for WIMPs with masses in the range 10-10⁴ GeV, we consider the challenging phenomenology of an MeV DM in a Z' portal model. Besides seeking to improve the search for WIMPs, it is worth considering the case in which DM and SM interact so feebly that they had never reached equilibrium. Feebly interacting massive particles (FIMPs) are DM candidates produced from the SM thermal bath in out-of-equilibrium processes, a mechanism called freeze-in. We show that if heavy fields (10¹⁰-10¹⁶ GeV) mediate the DM-SM interactions, the freeze-in is a natural possibility that provide the right amount of DM in the universe without the need of extremely small gauge, yukawa or quartic couplings. Such heavy fields are actually needed in theoretically well motivated high-energy scenarios like for instance GUT, seesaw, leptogenesis and inflation -- we call this interesting coincidence the "FIMP wonder". We explore different realizations of such possibility, with models involving moduli, fermions, gauge bosons and spin-2 fields as heavy mediators. We finally show in which cases the DM production during reheating have impact on the parameter space of such models
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Lundström, Erik. "Phenomenology of Inert Scalar and Supersymmetric Dark Matter." Doctoral thesis, Stockholms universitet, Fysikum, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-39278.
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While the dark matter has so far only revealed itself through the gravitational influence it exerts on its surroundings, there are good reasons to believe it is made up by WIMPs – a hypothetical class of heavy elementary particles not encompassed by the Standard Model of particle physics. The Inert Doublet Model constitutes a simple extension of the Standard Model Higgs sector. The model provides a new set of scalar particles, denoted inert scalars because of their lack of direct coupling to matter, of which the lightest is a WIMP dark matter candidate. Another popular Standard Model extension is that of supersymmetry. In the most minimal scenario the particle content is roughly doubled, and the lightest of the new supersymmetric particles, which typically is a neutralino, is a WIMP dark matter candidate. In this thesis the phenomenology of inert scalar and supersymmetric dark matter is studied. Relic density calculations are performed, and experimental signatures in indirect detection experiments and accelerator searches are derived. The Inert Doublet Model shows promising prospects for indirect detection of dark matter annihilations into monochromatic photons. It is also constrained by the old LEP II accelerator data. Some phenomenological differences between the Minimal Supersymmetric Standard Model and a slight extension, the Beyond the Minimal Supersymmetric Standard Model, can be found. Also, supersymmetric dark matter models can be detected already within the early LHC accelerator data.
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Mack, Gregory Daniel. "Constraining the particle nature of dark matter model-independent tests from the intersection of theory and observation /." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1211486940.
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Ekström, Patrik. "A Dark Matter Search with AMANDA : Limits on the Muon Flux from Neutralino Annihilations at the Centre of the Earth with 1997-99 Data." Doctoral thesis, Stockholm University, Department of Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-154.
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The nature of the dark matter in the Universe is one of the greatest mysteries in modern astronomy. The neutralino is a nonbaryonic dark matter candidate in minimal supersymmetric extensions to the standard model of particle physics. If the dark matter halo of our galaxy is made up of neutralinos some would become gravitationally trapped inside massive bodies like the Earth. Their pair-wise annihilation produces neutrinos that can be detected by neutrino experiments looking in the direction of the centre of the Earth.
The AMANDA neutrino telescope, currently the largest in the world, consists of an array of light detectors buried deep in the Antarctic glacier at the geographical South Pole. The extremely transparent ice acts as a Cherenkov medium for muons passing the array and using the timing information of detected photons it is possible to reconstruct the muon direction.
A search has been performed for nearly vertically upgoing neutrino induced muons with AMANDA-B10 data taken over the three year period 1997-99. No excess above the atmospheric neutrino background expectation was found. Upper limits at the 90 % confidence level has been set on the annihilation rate of neutralinos at the centre of the Earth and on the muon flux induced by neutrinos created by the annihilation products.
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Benito, María. "Dark matter in the Milky Way : uncertainties on its distribution and implications on its particle nature /." São Paulo, 2019. http://hdl.handle.net/11449/181227.
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Orientador: Fabio IoccoBanca: Edurado Ponton Bayona
Banca: Carola Dobrigkeit Chinellato
Banca: Luis Raul Weber Abramo
Abstract: The detailed knowledge of the dark matter (DM) distribution in the Milky Way (MW) is important for understanding the interplay between baryons and DM in the processes involved in galaxy formation and evolution. It is further a key element for experiments that aim to directly or indirectly detect the DM particle due to theoretically predicted non-negligible, weak interactions between DM and Standard Model particles. In this thesis, we aim to determine the distribution of DM in our Galaxy. First, we constrain the density profile of the DM halo by means of kinematical tracers of the total gravitational potential. We use objects in circular orbits around the Galactic centre (GC) as tracers of the total dynamical mass. By subtracting from the observed rotation velocities the velocities predicted for the visible component of the Galaxy (stars plus gas) -under the assumption of Newtonian gravity- we derive constraints on the DM distribution in the MW once a given parameterisation for the DM density profile is adopted. For the distribution of the visible, baryonic component of the Galaxy, we adopt a large array of observationally inferred, three-dimensional density profiles. In this way, we bracket current uncertainties on the shape and the normalisation of the Galactic visible component. Our determination of the DM density profile in the MW proceeds from astrophysical observations. These observations have sizeable uncertainties that need to be properly taken into account. We further... (Complete abstract click electronic access below)
Resumo: O conhecimento detalhado da distribuição da matéria escura na Via Láctea é importante para a compreensão da interação entre bariões e matéria escura nos processos envolvidos na formação e evolução das galáxias. Além disso, é um elemento-chave para experimentos que objetivam detectar direta ou indiretamente a partícula de matéria escura devido a interações fracas, desprezíveis e teoricamente previstas entre as partículas de matéria escura e Modelo Padrão. Nesta tese, pretendemos determinar a distribuição da matéria escura na nossa galáxia. Primeiro, restringimos o perfil de densidade do halo matéria escura por meio de traçadores cinemáticos do potencial gravitacional total. Usamos objetos em órbitas circulares ao redor do centro galáctico como traçadores da massa dinâmica total. Ao subtrair das velocidades de rotação observadas as velocidades previstas para o componente visível da galáxia (estrelas mais gás) - sob a hipótese da gravidade newtoniana - derivamos restrições na distribuição da matéria escura na nossa Galáxia, uma vez que uma dada parametrização para o perfil de densidade da matéria escura é adotado. Para a distribuição do componente visível e bariônico da Galáxia, adotamos uma grande variedade de perfis de densidade tridimensionais observados e inferidos. Desta forma, colocamos as incertezas atuais na forma e na normalização do componente visível Galáctico. Nossa determinação do perfil de densidade da matéria escura na Galáxia provém de observações astrofísicas. Essas observações têm incertezas consideráveis que precisam ser devidamente levadas em conta. Além disso, apresentamos uma análise que quantifica as incertezas astrofísicas que afetam a determinação da distribuição da matéria escura na Via Láctea e, portanto, a interpretação dos... (Resumo completo, clicar acesso eletrônico abaixo)
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