Well motivated theoretical models predict the annihilation of dark matter (DM) into standard model particles, a phenomenon which could be a significant source of photons in the gamma-ray sky. With its unprecedented sensitivity and its broad energy range (20 MeV to more than 300 GeV) the main instrument on board the Fermi satellite, the Large Area Telescope (LAT), might be able to detect an indirect signature of DM annihilations. In this work we revisit several interesting claims of extended dark matter emission made from analyses of Fermi-LAT data: First, based on three years of Fermi Large Area Telescope (LAT) gamma-ray data of the Virgo cluster, evidence for an extended emission associated with dark matter pair annihilation in the bb̄ channel has been reported by Han et al. (arxiv:1201.1003). After an in depth spatial and temporal analysis, we argue that the tentative evidence for a gamma-ray excess from the Virgo cluster is mainly due to the appearance of a population of previously unresolved gamma-ray point sources in the region of interest. These point sources are not part of the LAT second source catalogue (2FGL), but are found to be above the standard detection significance threshold when three or more years of LAT data is included. Second, we confirm the detection of a spatially extended excess of 2-5 GeV gamma rays from the Galactic Center (GC), consistent with the emission expected from annihilating dark matter or an unresolved population of about 10³ milisecond pulsars. However, there are significant uncertainties in the diffuse galactic background at the GC. We have performed a revaluation of these two models for the extended gamma ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsars population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of order a 10³ MSPs with parameters consistent with the average spectral shape of Fermi-LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure τ⁺τ⁻ annihilation channel is not a good fit to the data. But a mixture of τ⁻τ⁻ and bb̄ with a (σν) of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit. We also consider the possibility that the GeV excess is due to nonthermal bremsstrahlung produced by a population of electrons interacting with neutral gas in molecular clouds. The millisecond pulsars and dark matter alternatives have spatial templates well fitted by the square of a generalized Navarro-Frenk-White (NFW) profile with inner slope γ = 1.2. We model the third option with a 20-cm continuum emission Galactic Ridge template. A template based on the HESS residuals is shown to give similar results. The gamma-ray excess is found to be best fit by a combination of the generalized NFW squared template and a Galactic Ridge template. We also find the spectra of each template is not significantly affected in the combined fit and is consistent with previous single template fits. That is, the generalized NFW squared spectrum can be fit by either of order 10³ unresolved MSPs or DM with mass around 30 GeV, a thermal cross section, and mainly annihilating to bb̄ quarks. While the Galactic Ridge continues to have a spectrum consistent with a population of nonthermal electrons whose spectrum also provides a good fit to synchrotron emission measurements. We also show that the current DM fit may be hard to test, even with 10 years of Fermi-LAT data, especially if there is a mixture of DM and MSPs contributing to the signal, in which case the implied DM cross section will be suppressed.

In this thesis we consider a number of past, present, and future neutrino experiments designed to test physics beyond the Standard Model. First, we analyze potential new physics explanations of the NuTeV anomaly and check their compatibility with the most recent experimental data. The models we consider are: gauged Lmu-Ltau, gauged B-3Lmu, and S1, S3, V1, V3 leptoquarks. We find that only the triplet leptoquark models can explain NuTeV and be compatible with the data from other experiments at the same time, and only if the components of the triplet have different masses. Then, we analyze the prospects of discovery of heavy Majorana neutrinos (neutrissimos) suggested by the Okamura model at the LHC. We find that these particles, if produced, will live short enough to decay inside of the detector, while long enough to lead to a narrow peak in the invariant mass spectrum of the decay products. We estimate the typical masses of the neutrissimos to be in the TeV range. However, studies exist that have shown that if their masses are larger than about 150 GeV then the production cross-section is too small to lead to an observable event rate. Thus, we conclude that it will not be possible to detect the neutrissimo at the LHC unless its mass is smaller that about 150 GeV which corresponds to a very small region close to the edge of the parameter space of the Okamura model. Nevertheless, we argue that the signature of the neutrissimo may be detectable in other neutrino experiments which may be carried out in the future. As examples, we consider the NuSOnG experiment, which is a fixed target neutrino scattering experiment proposed at Fermilab, and a hypothetical long-baseline neutrino oscillation experiment in which the Fermilab NUMI beam is aimed at the Hyper-Kamiokande detector in Japan. In addition to the sensitivity to neutrissimos, we analyze the capabilities of these experiments to constraint the coupling constants and masses of new particles in various models of new physics suggested in the literature. The models we consider are: neutrissimo models, models with generation distinguishing Z's such as topcolor assisted technicolor, models containing various types of leptoquarks, R-parity violating SUSY, and extended Higgs sector models. In several cases, we find that the limits thus obtained could be competitive with those expected from direct searches at the LHC. In the event that any of the particles discussed here are discovered at the LHC, then the observation, or non-observation, of these particles in the NuSOnG and Fermilab-to-Hyper-Kamiokande experiments could help in identifying what type of particle had been observed. / Ph. D.

Neste trabalho realizamos uma abordagem fenomenológica da observação de novos bósons de spin-1 associados ao setor de Quebra de Simetria Eletrofraca. Como motivação a essa análise estudamos primeiramente o caso especial de modelos baseados no mecanismo de Quebra espontânea de Simetria por Condições de Contorno, os quais também apresentam uma torre de bósons vetoriais de Kaluza-Klein assegurando a unitariedade no espalhamento entre bósons gauge. Na análise fenomenológica efetuamos uma abordagem independente de modelo analisando o potencial do Large Hadron Collider (LHC) na detecção de novos bósons vetoriais associados ao setor de quebra de simetria. / In this work we performed a phenomenological observation of new spin-1 bosons associated with the Electroweak Symmetry Breaking sector. As motivation for this analysis we previously studied the special case of models based on the mechanism of Eletroweak Symmetry Breaking via Boundary Conditions, which also have a tower vector of Kaluza-Klein bosons ensuring unitarity in scattering between gauge bosons. In the phenomenological analysis we performed a model independent approach to analyzing the potential of the Large Hadron Collider (LHC) in the detection of new vector bosons associated with the symmetry breaking sector.

A search for quantum black holes with color charge decaying to one electron and one quark has been performed using data collected by the ATLAS Experiment at the Large Hadron Collider corresponding to 2.29 fb−1. No excess over the expected Standard Model interactions has been observed. Limits are set on the production cross section for events with one electron and one jet resulting from new physical phenomena. Models with a combined invariant mass of the electron and jet larger than or equal to 2.5TeV and a cross section above 2.6 fb are excluded at the 95% confidence level. This allows the exclusion of a significant part of the parameter space of quantum black hole models.

Neste trabalho realizamos uma abordagem fenomenológica da observação de novos bósons de spin-1 associados ao setor de Quebra de Simetria Eletrofraca. Como motivação a essa análise estudamos primeiramente o caso especial de modelos baseados no mecanismo de Quebra espontânea de Simetria por Condições de Contorno, os quais também apresentam uma torre de bósons vetoriais de Kaluza-Klein assegurando a unitariedade no espalhamento entre bósons gauge. Na análise fenomenológica efetuamos uma abordagem independente de modelo analisando o potencial do Large Hadron Collider (LHC) na detecção de novos bósons vetoriais associados ao setor de quebra de simetria. / In this work we performed a phenomenological observation of new spin-1 bosons associated with the Electroweak Symmetry Breaking sector. As motivation for this analysis we previously studied the special case of models based on the mechanism of Eletroweak Symmetry Breaking via Boundary Conditions, which also have a tower vector of Kaluza-Klein bosons ensuring unitarity in scattering between gauge bosons. In the phenomenological analysis we performed a model independent approach to analyzing the potential of the Large Hadron Collider (LHC) in the detection of new vector bosons associated with the symmetry breaking sector.

Eine Suche nach dem Zerfall B → π τ ν wird vorgestellt. Die Suche wird auf dem vollständigen Belle Datensatz durchgeführt, der 772E6 B anti-B Paare beinhaltet, die auf der Y(4s) Resonanz mit Belle Detektor am asymmetrischen e+e- KEKB Beschleuniger gesammelt wurden. Das τ Lepton wird in den Zerfallskanälen τ → e ν ν, τ → μ ν ν, τ → π ν und τ → ρ ν rekonstruiert. Eines der beiden B Mesonen, das Btag, wird mittels eines auf NeuroBayes beruhenden Algorithmus vollständig in einem hadronischen Zerfallskanal rekonstruiert. Der Rest des Kollisionsereignisses beinhaltet genau zwei geladene Spuren im Falle eines Signalzerfalls. Die weitere Trennung zwischen Signal und Untergrund wird mithilfe von Boosted Decision Trees durchgeführt. Ein Fit wird in der Verteilung der Extra Energie im elektromagnetischen Kalorimeter ECL, welche definiert ist als alle Energie die weder vom Btag noch von der rekonstruierten Signalseite stammt, durchgeführt. Kein signifikantes Signal wird beobachtet und ein oberes Limit von Br( B → π τ ν ) < 2.5E-4 basierend auf einem Vertrauensintervall von 90% wird bestimmt. Das Ergebnis ist in guter Übereinstimmung mit der Vorhersage des Standard Modells.

La réévaluation théorique du flux d'antineutrinos émis par les réacteurs nucléaires a révélé un déficit de 6% entre le flux observé et le flux attendu. Cette anomalie des antineutrinos de réacteur est significative à 2.7 σ, et une possible interprétation de ce résultat est l'existence d'un état stérile léger du neutrino vers lequel les neutrinos pourraient osciller à très courte distance. Le projet STEREO présenté dans ce manuscrit a pour objectif de prouver ou d'infirmer l'existence d'une telle oscillation.L'expérience est installée près (~10 m) du cœur compact du réacteur de recherche de l'Institut Laue-Langevin (ILL) à Grenoble, France, qui produit un important flux d'antineutrinos électroniques avec une énergie comprise entre 1 et 10 MeV. Le volume utile du détecteur STEREO consiste en une structure de 2 m3 segmentée en six cellules identiques remplies de scintillateur liquide dopé au gadolinium et alignées dans la direction du cœur. La détection s'effectue à l'aide de la réaction beta-inverse.Cette configuration offre une excellente sensibilité à une éventuelle oscillation à courte distance en mesurant la distorsion relative du spectre des antineutrinos dans chaque cellule en fonction de l'énergie et de la distance.Les lignes expérimentales de faisceaux de neutrons de l'ILL produisent un fort bruit de fond qui a été caractérisé à l'occasion de plusieurs campagnes de mesure. Leur analyse a permis de valider le design des lourds blindages passifs installés autour du détecteur et de la zone d'installation pour modérer leurs effets sur l’expérience STEREO.De plus, un détecteur supplémentaire est installé au-dessus de STEREO pour signaler la présence d'un muon issu du rayonnement cosmique et définir un veto aux mesures physiques. Ces muons, lors de leur passage à travers les blindages du détecteur, peuvent produire des neutrons rapides capables d’imiter le signal attendu par les antineutrinos. Il est donc essentiel de définir un veto qui soit le plus efficace et homogène possible.Il prend la forme d'une cuve de 2.5 m3 remplie d'eau dont la détection est basée sur l’effet Tcherenkov. Cette lumière émise par le passage des muons est récoltée sur 20 tubes photomultiplicateurs répartis au-dessus de la cuve et un additif est rajouté dans l'eau pour améliorer la collection de lumière sur les photomultiplicateurs.Ce veto à muons couvre complètement le détecteur STEREO ainsi que ces blindagesL'étude de plusieurs configurations de ce veto à muons sous la forme de prototypes avant la construction de l'instrument final a permis de définir une méthode de déclenchement du signal pour les muons extrêmement efficace tout en conservant une sensibilité réduite aux autres particules. Ces nombreux tests ont par ailleurs permis la validation et l'optimisation de l'électronique développée pour l'expérience au LPSC qui est la même pour le détecteur STEREO et pour le veto à muons.Après avoir caractérisé le flux de muons sur place et l'efficacité du veto à muons, une simulation a été développée et a permis d'évaluer le nombre de faux événements dus à ces neutrons. Ainsi, ce résultat a confirmé les prérequis scientifiques de l'expérience, à savoir la capacité à sonder l'anomalie des antineutrinos de réacteur en 300 jours de données réacteur.Le détecteur est actuellement en place sur site et prévoit de livrer ses premiers résultats fin 2016. / The re-evaluation of the theoretical antineutrino flux emitted by nuclear reactors revealed a deficit of about 6% between the observed flux and the expected one. This so-called reactor antineutrino anomaly has a statistical significance of 2.7σ, and one possible explanation to this deficit could be the existence of a light sterile neutrino state into which reactor antineutrino oscillate at very short distances. The STEREO project, which will be presented in this thesis, aims to find an evidence of such oscillation.The measurement will take place at only few meters (~10 m) from the compact core of the Institut Laue-Langevin (ILL) research reactor in Grenoble, France, which provides a large flux of electron antineutrinos with an energy range from 1 to 10 MeV. The sensitive volume of the STEREO detector is 2m3 of organic liquid scintillator doped with Gadolinium, consisting of 6 cells stacked along the direction of the core and detecting anti-neutrinos via inverse beta decay.This setup will provide excellent sensitivity to short-baseline oscillations effects by precisely measuring any relative distortion of the antineutrino spectrum as a function of both energy and baseline.Close proximity to the reactor yield a high background environment from nearby experiments that is managed through heavy shielding surrounding the detector. Many measurements campaign has been performed to characterized this background and had allowed the improvement of the passive shielding design installed on-site.Moreover, an additional detector is settled above STEREO to tag the presence of an incoming cosmic muon and define a muon veto. These muons will produce fast neutrons during their interaction through the shieldings of STEREO and these neutrons can mimick the expected antineutrino signal. Therefore it is crucial to define the most efficient and homogenous veto to these muons.It consists of a tank of 2.5m3 of water detecting muons by their Cerenkov radiation. The light emitted is collected thanks to 20 photomultipliers positionned at the top of the tank and a chemical compound is added into the water to improve the light collection on the photomultipliers.This muon veto fully covers the STEREO detector along with its shieldings.Several configurations of the muon veto system using prototypes before the final instrumental has allowed to define a trigger system which allows an excellent efficiency to cosmic muons regarding a little sensitivity to others particles. These numerous tests were also used to check and optimize the dedicated electronics builded at LPSC, which is the same for both the STEREO detector and muon veto.After characterization of the muon flux on site and with respect to the muon veto efficiency, a simulation has been developped to evaluate the rate of fake antineutrino event expected from the muon-induced fast neutrons. Thus, this result has confirmed the scientific requirements of the experience, which is the ability to probe the reactor antineutrino anomaly in 300 days of reactor data.STEREO is at the moment being comissionned and will deliver his first results at the end of 2016.

This dissertation is focused on three lines of work. In the first part, we consider aspects of holography and gauge/gravity duality in lower and higher dimensions. In particular, we study the duality for exact solutions localized on the Randal-Sundrum 2-branes. We also test if some holographic principles in general relativity can be generalized to include higher derivative theories of gravity; namely Lovelock gravity. In the second part we consider the role of pseudo Nambu-Goldstone bosons (pNGBs) in inflationary cosmology. Specifically, we construct an inflationary model using string theory axions, and use these pNGBs to produce the observed coherent magnetic field in the Universe. The third part of the thesis is devoted to the study of the phenomenology of emergent phenomena. we investigated whether one could test if diffeomorphism invariance, the sacred symmetry of general relativity, is emergent. We also construct a new minimal vectorial Standard Model, and argue that the absence of mirror particles predicted by this model can give us a hint about the fundamental nature of space.

No description available.

Orientador: Orlando Luis Goulart Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T13:51:02Z (GMT). No. of bitstreams: 1 Lessa_AndrePaniago_M.pdf: 1406320 bytes, checksum: ef9057a3046500f72b58ec6a9a5e266f (MD5) Previous issue date: 2007 / Resumo: O modelo padrão das partículas elementares, baseado na invariância de Lorentz e na simetria de gauge SU(3)c Ä SU(2)L Ä U(1)Y, foi confirmado por todos os testes experimentais até o momento. No entanto, nada nos garante que é este o modelo final das interações fundamentais. Problemas teóricos como a hierarquia, o número de gerações de partículas e a assimetria bariônica e alguns dados experimentais (neutrinos massivos, matéria e energia escura) sugerem a necessidade de física além do Modelo Padrão (SM). Alguns destes problemas são resolvidos em uma importante classe de modelos, que assumem a existência de simetrias espaciais adicionais, chamada de supersimetria. A proposta deste projeto é estudar a idéia de supersimetria e sua possível relevância para a física além do Modelo Padrão. Para entendermos o princípio da supersimetria, iremos construir o Modelo Padrão Supersimétrico Mínimo (MSSM) e apresentar algumas de suas conseqüências fenomenológicas. Também serão apresentados os modelos mSUGRA e mGMSB, assim como algumas de suas principais características. Em Anexo apresentaremos algumas informações complementares, além de um trabalho desenvolvido em paralelo com o projeto de Mestrado / Abstract: The standard model of elementary particles, based in Lorentz invariance and in the gauge symmetries SU(3)c Ä SU(2)L Ä U(1)Y, was confirmed by all experimental data so far. However there is no evidence that it is the final theory of fundamental interactions. In fact, several theoretical evidences, such as the hierarchy problem, baryogenesis and the number of families and a few experimental data (neutrino masses, dark matter and dark energy) suggest that we should look for physics beyond the Standard Model (SM). Some of these problems are solved in an important class of models, which assume the existence of additional spatial symmetries, called supersymmetry. The objective of this thesis is to study the concept of supersymmetry and its potential relevance to the physics beyond the Standard Model. To understand the principle of supersymmetry we will construct the Minimal Supersymmetric Standard Model (MSSM) and present some of its phenomenological consequences. We will also present the mSUGRA and mGMSB models, as well as some of its properties. In the Appendix we show some complementary information and a parallel work developed during this project / Mestrado / Física das Particulas Elementares e Campos / Mestre em Física