Baryon Asymmetry of the Universe in the NuMSM

We perform a detailed analysis of baryon asymmetry generation in the NuMSM (an extension of the Standard Model by three singlet Majorana fermions with masses below the Fermi scale). Fixing a number of parameters of the NuMSM by the neutrino oscillation data, we determine the remaining domain of the parameter space from the requirement of successful baryogenesis. We derive, in particular, the constraints on the mass splitting of a pair of singlet fermions, and on the strength of their coupling to ordinary leptons, essential for searches of these particles in rare decays of mesons and in beam-dump experiments with intensive proton beams.

Neutrinoless double beta decay and low scale leptogenesis

Marco Drewes, Shintaro Eijima

The extension of the Standard Model by right handed neutrinos with masses in the GeV range can simultaneously explain the observed neutrino masses via the seesaw mechanism and the baryon asymmetry of the universe via leptogenesis. It has previously been claimed that the requirement for successful baryogenesis implies that the rate of neutrinoless double beta decay in this scenario is always smaller than the standard prediction from light neutrino exchange alone. In contrast, we find that the rate for this process can also be enhanced due to a dominant contribution from heavy neutrino exchange. In a small part of the parameter space it even exceeds the current experimental limit, while the properties of the heavy neutrinos are consistent with all other experimental constraints and the observed baryon asymmetry is reproduced. This implies that neutrinoless double beta decay experiments have already started to rule out part of the leptogenesis parameter space that is not constrained by any other experiment, and the lepton number violation that is responsible for the origin of baryonic matter in the universe may be observed in the near future. (C) 2016 The Authors. Published by Elsevier B.V.

Elsevier2016

Dark matter, baryogenesis and neutrino oscillations from right-handed neutrinos

Laurent Canetti, Marco Drewes, Tibor Frossard

We show that, leaving aside accelerated cosmic expansion, all experimental data in high energy physics that are commonly agreed to require physics beyond the Standard Model can be explained when completing the model by three right-handed neutrinos that can be searched for using present-day experimental techniques. The model that realizes this scenario is known as the Neutrino Minimal Standard Model (nu MSM). In this article we give a comprehensive summary of all known constraints in the nu MSM, along with a pedagogical introduction to the model. We present the first complete quantitative study of the parameter space of the model where no physics beyond the nu MSM is needed to simultaneously explain neutrino oscillations, dark matter, and the baryon asymmetry of the Universe. The key new point of our analysis is leptogenesis after sphaleron freeze-out, which leads to resonant dark matter production, thus evading the constraints on sterile neutrino dark matter from structure formation and x-ray searches. This requires one to track the time evolution of left-and right-handed neutrino abundances from hot big bang initial conditions down to temperatures below the QCD scale. We find that the interplay of resonant amplifications, CP-violating flavor oscillations, scatterings, and decays leads to a number of previously unknown constraints on the sterile neutrino properties. We furthermore reanalyze bounds from past collider experiments and big bang nucleosynthesis in the face of recent evidence for a nonzero neutrino mixing angle theta(13). We combine all our results with existing constraints on dark matter properties from astrophysics and cosmology. Our results provide a guideline for future experimental searches for sterile neutrinos. A summary of the constraints on sterile neutrino masses and mixings has appeared in Canetti et al. [Phys. Rev. Lett. 110, 061801 (2013)]. In this article we provide all details of our calculations and give constraints on other model parameters.

Amer Physical Soc2013

Reconciling resonant leptogenesis and baryogenesis via neutrino oscillations

Juraj Klaric, Inar Timiryasov

Right-handed neutrinos offer an elegant solution to two well-established phenomena beyond the Standard Model (SM)-masses and oscillations of neutrinos, as well as the baryon asymmetry of the Universe. It is also a minimalistic solution, since it requires only singlet Majorana fermions to be added to the SM particle content. If these fermions are nearly degenerate, the mass scale of right-handed neutrinos can be very low and accessible by the present and planned experiments. There are at least two well-studied mechanisms of low-scale leptogenesis: baryogenesis via oscillations and resonant leptogenesis. These two mechanisms were often considered separate, but they can, in fact, be understood as two different regimes of one and the same mechanism, described by a unique set of quantum kinetic equations. In this work, we show, using a unified description based on quantum kinetic equations, that the parameter spaces of these two regimes of low-scale leptogenesis significantly overlap. We present a comprehensive study of the parameter space of low-scale leptogenesis with the mass scale ranging from 0.1 to similar to 10(6) GeV. The unified perspective of this work reveals the synergy between intensity and energy frontiers in the quest for heavy Majorana neutrinos.

AMER PHYSICAL SOC2021

Dark matter, baryogenesis and neutrino oscillations from right-handed neutrinos

Laurent Canetti, Marco Drewes, Tibor Frossard

Amer Physical Soc2013