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Phenomenology of low-scale Seesaw Models
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| dc.contributor.advisor | Hernández Gamazo, Pilar | |
| dc.contributor.author | Kekic, Marija | |
| dc.contributor.other | Departament de Fisica Teòrica | es_ES |
| dc.date.accessioned | 2016-12-09T11:12:57Z | |
| dc.date.available | 2016-12-10T05:45:05Z | |
| dc.date.issued | 2016 | es_ES |
| dc.date.submitted | 22-12-2016 | es_ES |
| dc.identifier.uri | http://hdl.handle.net/10550/56301 | |
| dc.description.abstract | All the observed particles are well accommodated in the Standard Model, together with the basic forces. However, there are both experimental and theoretical hints that the Standard Model can not be a complete theory and that New Physics is needed. Some of the theoretical problems are: i) The flavor-puzzle, i.e., why are there three copies of particles differing only by their mass. Most of the free parameters in the Standard Model are linked to this puzzle. They have been measured, but their values do not follow any clear pattern and their origin remains elusive. ii) The strong CP problem, that is, why the CP symmetry is conserved in the strong interactions in the Standard Model, which is not ensured by any gauge symmetry. iii) How to combine quantum mechanics with general relativity, since the attempts to do this lead to non-renormalizable theories. Furthermore, gravity necessarily introduces a new scale, the Planck scale, which leads to the hierarchy problem. iv)The hierarchy problem: why is the electroweak scale so much smaller than the Planck mass. If there were new particles heavier than the electroweak scale, their coupling with the Higgs boson would induce quantum corrections to the Higgs mass naturally of the order of those higher masses. On the other hand, there are also experimental hints for physics beyond the Standard Model :i) Neutrinos were assumed massless in the SM but the well established phenomena of neutrino oscillations implies that they are massive, and the SM has to be modified. ii)The dominance of baryons over antibaryons in the Universe can not be explained within the SM. iii) The origin of Dark Matter that accounts for 25 % of the gravitating matter in the Universe. A solution to this problem might lie in the existence of a new weakly-interacting particle that is not yet discovered. iv) The dark energy, a force responsible for the Universe's accelerating expansion, contributes to 70% of the total energy in the Universe. The nature of this energy is unknown. Two of the mentioned hints, non-zero neutrino masses and the baryon asymmetry, will be addressed in the thesis in the context of the low-scale Seesaw Models. Low-scale Seesaw Models are the minimal extensions of the Standard Model (SM) that can explain neutrino masses and are potentially testable in the next generation experiments. These models add two or three extra singlet (sterile) fermions to the SM, with masses below the electroweak scale. The main goal of this thesis is to study the impact of these extra states in the Early Universe. The thesis is divided in two parts, the first one covers a lengthy introduction and background material for understanding the original results of this work. The plan of this thesis is as follows: In Chapter I we motivate the need for new physics beyond the Standard Model. In Chapter II we give a brief review of the Standard Model, the theory that has been experimentally confirmed at the highest energies probed by current collider experiments. On the other hand, neutrinos were assumed massless in the Standard Model while oscillation experiments have demonstrated that neutrinos have non vanishing masses. In Chapter III we give a list of the most popular extensions of the Standard Model that can explain light neutrino masses. In Chapter IV, we summarize what is known about the lepton flavour sector of the Standard Model, focusing particularly on the phenomenology of the low-scale Seesaw Models. In Chapter V we give the motivation for the mass scale of the extra fermions in these models, the parametrization of the models and the current and future experimental constraints on the model parameters. In Chapter VI we give a brief review of the Standard Cosmological Model, and in Chapter VII we discuss the thermodynamics of the Early Universe plasma. In Chapter VIII we focus on the sterile neutrino evolution before the electroweak phase transition, where they can seed the observed matter-antimatter asymmetry in the Universe. The evolution of the sterile neutrinos after the electroweak phase transition and their impact on the cosmological parameters is given in Chapter IX. Finally, in Chapter X we summarize the main scientific results in this work, divided in four publications, that are reproduced in full in Part II of the thesis. | es_ES |
| dc.format.extent | 276 p. | es_ES |
| dc.language.iso | en | es_ES |
| dc.subject | low scale seesaw | es_ES |
| dc.subject | cosmology | es_ES |
| dc.subject | baryogenesis | es_ES |
| dc.subject | sterile neutrino | es_ES |
| dc.title | Phenomenology of low-scale Seesaw Models | es_ES |
| dc.type | doctoral thesis | es_ES |
| dc.subject.unesco | UNESCO::FÍSICA | es_ES |
| dc.embargo.terms | 0 days | es_ES |
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