Strong washout approximation to resonant leptogenesis
Abstract
We show that the effective decay asymmetry for resonant Leptogenesis in the strong washout regime with two sterile neutrinos and a single active flavour can in wide regions of parameter space be approximated by its latetime limit ε=Xsin(2φ)/(X{sup 2}+sin{sup 2}φ), where X=8πΔ/(Y{sub 1}{sup 2}+Y{sub 2}{sup 2}), Δ=4(M{sub 1}M{sub 2})/(M{sub 1}+M{sub 2}), φ=arg(Y{sub 2}/Y{sub 1}), and M{sub 1,2}, Y{sub 1,2} are the masses and Yukawa couplings of the sterile neutrinos. This approximation in particular extends to parametric regions where Y{sub 1,2}{sup 2}>> Δ, i.e. where the width dominates the mass splitting. We generalise the formula for the effective decay asymmetry to the case of several flavours of active leptons and demonstrate how this quantity can be used to calculate the lepton asymmetry for phenomenological scenarios that are in agreement with the observed neutrino oscillations. We establish analytic criteria for the validity of the latetime approximation for the decay asymmetry and compare these with numerical results that are obtained by solving for the mixing and the oscillations of the sterile neutrinos. For phenomenologically viable models with two sterile neutrinos, we find that the flavoured effective latetime decay asymmetry can be applied throughout parameter space.
 Authors:
 Physik Department T70, JamesFranckStraße, Technische Universität München, 85748 Garching (Germany)
 Publication Date:
 OSTI Identifier:
 22375874
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2014; Journal Issue: 09; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; ASYMMETRY; DECAY; FLAVOR MODEL; NEUTRINOS; PARTICLE PRODUCTION; SPACE
Citation Formats
Garbrecht, Björn, Gautier, Florian, and Klaric, Juraj, Email: garbrecht@tum.de, Email: florian.gautier@tum.de, Email: juraj.klaric@tum.de. Strong washout approximation to resonant leptogenesis. United States: N. p., 2014.
Web. doi:10.1088/14757516/2014/09/033.
Garbrecht, Björn, Gautier, Florian, & Klaric, Juraj, Email: garbrecht@tum.de, Email: florian.gautier@tum.de, Email: juraj.klaric@tum.de. Strong washout approximation to resonant leptogenesis. United States. doi:10.1088/14757516/2014/09/033.
Garbrecht, Björn, Gautier, Florian, and Klaric, Juraj, Email: garbrecht@tum.de, Email: florian.gautier@tum.de, Email: juraj.klaric@tum.de. Mon .
"Strong washout approximation to resonant leptogenesis". United States.
doi:10.1088/14757516/2014/09/033.
@article{osti_22375874,
title = {Strong washout approximation to resonant leptogenesis},
author = {Garbrecht, Björn and Gautier, Florian and Klaric, Juraj, Email: garbrecht@tum.de, Email: florian.gautier@tum.de, Email: juraj.klaric@tum.de},
abstractNote = {We show that the effective decay asymmetry for resonant Leptogenesis in the strong washout regime with two sterile neutrinos and a single active flavour can in wide regions of parameter space be approximated by its latetime limit ε=Xsin(2φ)/(X{sup 2}+sin{sup 2}φ), where X=8πΔ/(Y{sub 1}{sup 2}+Y{sub 2}{sup 2}), Δ=4(M{sub 1}M{sub 2})/(M{sub 1}+M{sub 2}), φ=arg(Y{sub 2}/Y{sub 1}), and M{sub 1,2}, Y{sub 1,2} are the masses and Yukawa couplings of the sterile neutrinos. This approximation in particular extends to parametric regions where Y{sub 1,2}{sup 2}>> Δ, i.e. where the width dominates the mass splitting. We generalise the formula for the effective decay asymmetry to the case of several flavours of active leptons and demonstrate how this quantity can be used to calculate the lepton asymmetry for phenomenological scenarios that are in agreement with the observed neutrino oscillations. We establish analytic criteria for the validity of the latetime approximation for the decay asymmetry and compare these with numerical results that are obtained by solving for the mixing and the oscillations of the sterile neutrinos. For phenomenologically viable models with two sterile neutrinos, we find that the flavoured effective latetime decay asymmetry can be applied throughout parameter space.},
doi = {10.1088/14757516/2014/09/033},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 09,
volume = 2014,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2014},
month = {Mon Sep 01 00:00:00 EDT 2014}
}

By including spectator fields into the Boltzmann equations for Leptogenesis, we show that partially equilibrated spectator interactions can have a significant impact on the freezeout value of the asymmetry in the strong washout regime. The final asymmetry is typically increased, since partially equilibrated spectators ''hide'' a part of the asymmetry from washout. We study examples with leptonic and nonleptonic spectator processes, assuming thermal initial conditions, and find up to 50% enhanced asymmetries compared to the limit of fully equilibrated spectators. Together with a comprehensive overview of the equilibration temperatures for various Standard Model processes, the numerical results indicate the rangesmore »

Resonant {tau} Leptogenesis with Observable Lepton Number Violation
We consider a minimal extension of the standard model with one singlet neutrino per generation that can realize resonant leptogenesis at the electroweak scale. In particular, the baryon asymmetry in the Universe can be created by leptontobaryon conversion of an individual lepton number, for example, that of the {tau} lepton. The current neutrino data can be explained by a simple CPviolating Yukawa texture. The model has several testable phenomenological implications. It contains heavy Majorana neutrinos at the electroweak scale, which can be probed at e{sup +}e{sup } linear colliders, and predicts e and {mu}leptonnumberviolating processes, such as 0{nu}{beta}{beta} decay, {mu}{yields}e{gamma},more » 
Electroweakscale resonant leptogenesis
We study minimal scenarios of resonant leptogenesis near the electroweak phase transition. These models offer a number of testable phenomenological signatures for lowenergy experiments and future highenergy colliders. Our study extends previous analyses of the relevant network of Boltzmann equations, consistently taking into account effects from out of equilibrium sphalerons and single lepton flavors. We show that the effects from single lepton flavors become very important in variants of resonant leptogenesis, where the observed baryon asymmetry in the Universe is created by leptontobaryon conversion of an individual lepton number, for example, that of the {tau}lepton. The predictions of such resonantmore » 
Electroweak resonant leptogenesis in the singlet Majoron model
We study resonant leptogenesis at the electroweak phase transition in the singlet Majoron model with righthanded neutrinos. We consider a scenario where the SM gauge group and the lepton number break down spontaneously during a secondorder electroweak phase transition. We calculate the flavor and temperaturedependent leptonic asymmetries, by including the novel contributions from the transverse polarizations of the W{sup {+}} and Z bosons. The required resummation of the gaugedependent, offshell, heavyneutrino selfenergies is consistently treated within the gaugeinvariant framework of the pinch technique. Taking into consideration the freezeout dynamics of sphalerons, we delineate the parameter space of the model thatmore » 
Resonant leptogenesis and tribimaximal leptonic mixing with A{sub 4} symmetry
We investigate the viability of thermal leptogenesis in typeI seesaw models with leptonic flavor symmetries that lead to tribimaximal neutrino mixing. We consider an effective theory with an A{sub 4}xZ{sub 3}xZ{sub 4} symmetry, which is spontaneously broken at a scale much higher than the electroweak scale. At the high scale, leptonic Yukawa interactions lead to exact tribimaximal mixing and the heavy Majorana neutrino mass spectrum is exactly degenerate. In this framework, leptogenesis becomes viable once this degeneracy is lifted either by renormalization group effects or by a soft breaking of the A{sub 4} symmetry. The implications for lowenergy neutrino physicsmore »