Добірка наукової літератури з теми "ARS leptogenesis"

We review the current status of the leptogenesis scenario originally proposed by Akhmedov, Rubakov and Smirnov (ARS). It takes place in the parametric regime where the right-handed neutrinos are at the electroweak scale or below and the CP-violating effects are induced by the coherent superposition of different right-handed mass eigenstates. Two main theoretical approaches to derive quantum kinetic equations, the Hamiltonian time evolution as well as the Closed-Time-Path technique are presented, and we discuss their relations. For scenarios with two right-handed neutrinos, we chart the viable parameter space. Both, a Bayesian analysis, that determines the most likely configurations for viable leptogenesis given different variants of flat priors, and a determination of the maximally allowed mixing between the light, mostly left-handed, and heavy, mostly right-handed, neutrino states are discussed. Rephasing invariants are shown to be a useful tool to classify and to understand various distinct contributions to ARS leptogenesis that can dominate in different parametric regimes. While these analyses are carried out for the parametric regime where initial asymmetries are generated predominantly from lepton-number conserving, but flavor violating effects, we also review the contributions from lepton-number violating operators and identify the regions of parameter space where these are relevant.

The focus of this paper lies on the possible experimental tests of leptogenesis scenarios. We consider both leptogenesis generated from oscillations, as well as leptogenesis from out-of-equilibrium decays. As the Akhmedov–Rubakov–Smirnov (ARS) mechanism allows for heavy neutrinos in the GeV range, this opens up a plethora of possible experimental tests, e.g. at neutrino oscillation experiments, neutrinoless double beta decay, and direct searches for neutral heavy leptons at future facilities. In contrast, testing leptogenesis from out-of-equilibrium decays is a quite difficult task. We comment on the necessary conditions for having successful leptogenesis at the TeV-scale. We further discuss possible realizations and their model specific testability in extended seesaw models, models with extended gauge sectors, and supersymmetric leptogenesis. Not being able to test high-scale leptogenesis directly, we present a way to falsify such scenarios by focusing on their washout processes. This is discussed specifically for the left–right symmetric model and the observation of a heavy [Formula: see text], as well as model independently when measuring [Formula: see text] washout processes at the LHC or neutrinoless double beta decay.

Abstract Extensions of the Standard Model (SM) with sterile neutrinos are well motivated from the observed oscillations of the light neutrinos and they have shown to successfully explain the Baryon Asymmetry of the Universe (BAU) through, for instance, the so-called ARS leptogenesis. Sterile neutrinos can be added in minimal ways to the SM, but many theories exist where sterile neutrinos are not the only new fields. Such theories often include scalar bosons, which brings about the possibility of further interactions between the sterile neutrinos and the SM. In this paper we consider an extension of the SM with two sterile neutrinos and one scalar singlet particle and investigate the effect that an additional, thermalised, scalar has on the ARS leptogenesis mechanism. We show that in general the created asymmetry is reduced due to additional sterile neutrino production from scalar decays. When sterile neutrinos and scalars are discovered in the laboratory, our results will provide information on the applicability of the ARS leptogenesis mechanism.

L'asymétrie entre matière et antimatière est un problème non résolu de la cosmologie. Une approche populaire pour l'expliquer est la leptogénèse avec des neutrinos stériles, qui sont des particules motivées expérimentalement pour expliquer les masses des neutrinos actifs du Modèle Standard. Il est possible d'inclure dans les scénarios de leptogénèse une transition de phase cosmologique qui donne leur masse aux neutrinos stériles. Cette idée est intéressante phénoménologiquement, car une transition de phase produit des ondes gravitationnelles pouvant être détectées. À la température de la transition de phase T, les neutrinos stériles obtiennent une masse M. Deux mécanismes sont considérés. Pour des neutrinos stériles non-relativistes M>T déviant de l'équilibre lors de la transition de phase, l'asymétrie leptonique est créée lors de leurs désintégrations. La rapidité de la transition permet d'avoir une population de neutrinos stériles initiale plus importante que dans le cas standard et améliore la création d'asymétrie. L'analyse numérique permet de décrire l'espace des paramètres où la leptogénèse est réussie. Pour des neutrinos stériles relativistes M
The baryon asymmetry in our Universe is an unsolved problem in cosmology. A popular approach for explaining it is leptogenesis with sterile neutrinos, which are particles motivated in order to explain the masses of active neutrinos in the Standard Model. It is possible to include in these scenarios a cosmological phase transition which gives rise to the sterile neutrino masses. This idea is phenomenologically interesting, as such a phase transition could produce detectable gravitational waves. At the temperature T of the phase transition, sterile neutrinos acquire a mass M. Two mechanisms are considered. For non-relativistic sterile neutrinos M>T, deviating from equilibrium due to the phase transition, they will quickly decay and produce a lepton asymmetry. The rapidity of the phase transition allows a larger sterile neutrino population than in usual scenarios and enhances the created asymmetry. Numerical analyses describe the successful regions in parameter space for leptogenesis. For relativistic sterile neutrinos M

Chapter 4 deals with the stability of the proton, hence of hydrogen, and how to reconcile that stability with the baryon number nonconservation (or baryon conservation) needed to establish a matter–antimatter imbalance in the infant universe. Sakharov’s three conditions for establishing a matter–antimatter imbalance are presented. Grand unified theories and experimental searches for proton decay are described. The concept of spontaneous symmetry breaking is introduced in describing the electroweak phase transition in the infant universe. That transition is treated as the potential site for introducing the imbalance between quarks and antiquarks, via either baryogenesis or leptogenesis models. The up–down quark mass difference is presented as essential for providing the stability of hydrogen and of the deuteron, which serves as a crucial stepping stone in stellar hydrogen-burning reactions that generate the energy and elements needed for life. Constraints on quark masses from lattice QCD calculations and violations of chiral symmetry are discussed.

In the context of a model that combines the type I and type II seesaw mechanisms, we investigate two different kinds of neutrino mass matrices that enable the production of tiny neutrino masses. The goal of this work is to examine how leptogenesis contributes to the matter-antimatter asymmetry's origin. The first mass matrix is of the tri-bimaximal (TBM) type, which consistently produces a reactor mixing angle that is non-zero, and is based on the type I seesaw mechanism. Next, we study the type II seesaw mass matrix with the goal of introducing perturbations from the TBM mixing pattern and matching the neutrino parameter best-fit values when type I and type II seesaw mechanisms are taken into account together. The type II seesaw matrix is handled by us as a hybrid textures matrix. We explore the roles of hybrid texturing mass matrices and TBM in shedding light on how neutrino CP phases affect the universe's baryon asymmetry.