Efectos de los momentos dipolares del v en la pérdida de energía estelar

En este proyecto de investigación estudiamos la sensibilidad del momento magnético y el momento dipolar eléctrico del neutrino en el marco del modelo electrodébil SU(2)L x U(1)Y x U(1)B—L y para energías y luminosidades de los futuros colisionadores lineales e+e—, como el ILC y el CLIC. Para nuestro estu- dio consideramos el proceso e+e— (Z, Z1, y) — vTvTy . Para las energías del centro de masa y luminosidades del colisionador de s = 1000 — 3000 GeV y L = 500 — 2000 fb—1, obtenemos límites al 95 % C.L. en los momentos dipolares |µT (µB)| <6.28 X 10—9 y |dvT (ecm)| <1.21 x 10-21, los cuales mejoran los límites existentes en la literatura en 2-3 órdenes de magnitud. Además, como parte del proyecto de investigación desarrollamos y presentamos fórmulas analíticas novedosas para evaluar los efectos de momento magnético y del momento dipolar eléctrico del neutrino en la tasa de pérdida de energía estelar a través del proceso de aniquilación e+e— (Y , Z, Z1) — VV. Nuestros resultados muestran que la pérdida de energía estelar depende significativamente de los momentos dipolares del neutrino, así como de los parámetros que caracterizan el modelo que adoptamos

Phenomenology of low-scale Seesaw Models

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

Topics in Physics Beyond the Standard Model

El Modelo Estándar (SM) de partículas es una teoría hermosa y extensamente contrastada. De hecho, sus éxitos son innumerables y algunas de sus predicciones, como el momento magnético anómalo de los electrones, se han confirmado con una precisión de una parte en 1010 (!). Sin embargo, y por suerte para mi doctorado, todavía hay preguntas abiertas que no se explican dentro del SM y requieren probablemente una dinámica subyacente o nueva física más allá del SM (BSM). Esta tesis explora, desde un punto de vista fenomenológico, algunas de las posibles extensiones del SM que permiten las preguntas abiertas en física fundamental: • El origen de las masas de los neutrinos • El origen de la asimetría entre materia y antimateria en el Universo • El origen de la materia oscura En este resumen, explicaremos brevemente estos tres problemas abiertos, así como las contribuciones originales planteadas en esta tesis para resolverlos, así como nuestras principales conclusiones. 1) Masas de los neutrinos: Uno de los resultados más importantes en tiempos recientes en física de partículas es el descubrimiento de las masas y mezclas de los neutrinos, tras varias décadas de experimentos con neutrinos cósmicos y haces producidos en aceleradores. Este descubrimiento ha dado lugar al premio Nobel en 2002 a los pioneros en la detección de neutrinos cósmicos (Prof. R.Davis and Prof. M. Koshiba), y en 2015 a los experimentos que obtuvieron los primeros resultados concluyentes, SuperKamiokande y SNO (Prof. Kajita and Prof. A. McDonald). Es fácil extender el SM para incorporar neutrinos masivos. Basta con hipotetizar la existencia de nuevos campos singletes, Ri, es decir sin carga electrodébil ni fuerte, de forma que un acoplamiento del tipo Yukawa entre los campos. En esta tesis estudiaremos extensiones del SM que permiten explicar estas masas tan pequeñas. 2) Dr.Jekyll y Mr.Hyde: aka asimetría materiaantimateria: El Universo que observamos está hecho esencialmente de materia. Los rayos cósmicos del Sol indican que está compuesto de materia. También el hecho de que Neil Armstrong sobreviviera a su paseo por la Luna implica que está hecha de materia. La supervivencia de los planetas en realidad demuestra que también el sistema solar está hecho esencialmente de materia. Los rayos cósmicos también proporcionan evidencia de la existencia de antimateria en la galaxia al nivel 10^-4 compatible con ser producida en objetos astrofísicos. En escalas más grandes, las evidencias son en realidad menos estrictas, aunque también a la escala de los cúmulos de galaxias hay evidencia de la ausencia de grandes cantidades de antimateria. En esta tesis hemos estudiado el mecanismo de Bariogénesis via leptogénesis, donde primero se genera una asimetría en un sector leptónico extendido, conectado posiblemente con las masas de los neutrinos, y es transferida a los bariones por los esfalerones a T >> 100GeV. 3) Materia Oscura: La materia oscura es mi rompecabezas favorito. De hecho, ahora es evidente que casi 25% del contenido del universo está hecho de materia que gravita pero no es bariónica. En realidad, no sabemos mucho de su naturaleza. Sabemos con certeza que no interactúa con la luz, es decir que no emite luz, ni la absorbe, y que además debe interactuar muy débilmente con el SM, porque de lo contrario la habríamos detectado. Por otra parte, la evidencia de sus interacciones gravitacionales es múltiple y proviene de una diversidad de fuentes, a diferentes escalas. En esta tesis he estudiado por una parte las distintas posibilidades de explicar la materia oscura en modelos de neutrinos masivos, que además predicen la asimetría bariónica. Además he hecho contribuciones novedosas a la posibilidad de detectar materia oscura en la forma de neutrinos masivos, mediante mapas de intensidad de rayos X, y la detección de la desintegración estimulada de axiones en radiofrecuencias.The Standard Model (SM) of particle physics is a beautiful and extremely well-verified theory. Indeed its successes are countless and some of its predictions, as the anomalous magnetic moment of the electrons, have been tested to one part in 1010(!). Nevertheless, and lucky enough for my Ph.D., there are still some missing pieces, puzzles that remain unexplained within the SM and most likely imply the existence of new physics beyond the SM (BSM). The SM is a wonderful theory as it is, however many aspects are unsatisfactory and puzzling even at the fundamental level, as we already noticed in the previous sections. For example: • Why are there three families? The number of fermion generation is completely arbitrary, still it has important consequences like CP violation; • Why is parity broken? In a sense one would not expect space to be asymmetric! • The large number of parameters as well as the arbitrariness of most of them challenge SM predictivity. There is for example no explanation to the large hierarchy in the pattern of quark and lepton masses as shown in Fig. 1.2. This is the problem S. Weinberg says he would like to solve (and he is thinking about it since 1972!). All these points are already an indication that the SM may require some extra physics to be a complete theory. But there is compelling evidence that the theory described above is not complete also from experimental data. In this doctoral thesis we have focused on different phenomenological and theoretical aspects of physics beyond the Standard Model. We focused on the collider phenomenology of sterile neutrinos models as well as on theoretical aspects related to their flavor symmetries. On the more cosmological side, we investigated minimal models that can explain neutrino masses, the matter-antimatter asymmetry as well as dark matter. In fact, a big puzzle of the SM is the fact that antimatter in the universe is only a very small part, much less abundant than matter. For example, cosmic rays from the Sun indicates that it is composed of matter. Also the fact that Neil Armstrong did survive demonstrates that the Moon is made of matter. The survival of planets actually demonstrates that the solar system is made essentially of matter Finally, we also dedicated some effort to propose new direct and indirect searches for dark matter. Dark Matter (DM) is actually my favorite SM puzzle. It has been firmly established that almost 25% of the gravitating energy content of the universe is non-baryonic. We do not know the nature of this component nor how it interacts, but we know that it does not emit nor absorb light. Moreover it should be very weakly interacting with all the particles of the SM, because otherwise we would had already detected it! DM induces a gravitational potential, a fact that has been established by a variety of observations at different scales. In particular we have evidence from galaxy rotation curves, gravitational lensing, and a variety of kinematical measurements. Also the observed temperature perturbations in the cosmic microwave background (CMB) point to a 26% of the energy content of the Universe being in the form of non-baryonic matter. In particular we have studied sterile neutrino dark matter and axion, using in particular X-ray and radio signals to look for their decay