Status of rates and rate equations for thermal leptogenesis

For leptogenesis with heavy sterile neutrinos above the electroweak scale, asymmetries produced at early times (in the relativistic regime) are relevant, if they are protected from washout. This can occur for weak washout or when the asymmetry is partly protected by being transferred to spectator fields. We thus study the relevance of relativistic effects for leptogenesis in a minimal seesaw model with two sterile neutrinos in the strongly hierarchical limit. Starting from first principles, we derive a set of momentum-averaged fluid equations to calculate the final B −L asymmetry as a function of the washout strength and for different initial conditions at order one accuracy. For this, we take the leading fluid approximation for the relativistic CP -even and odd rates. Assuming that spectator fields remain in chemical equilibrium, we find that for weak washout, relativistic corrections lead to a sign flip and an enhancement of the asymmetry for a vanishing initial abundance of sterile neutrinos. As an example for the effect of partially equilibrated spectators, we consider bottom-Yukawa and weak-sphaleron interactions in leptogenesis driven by sterile neutrinos with masses 5 × 10 12 GeV. For a vanishing initial abundance of sterile neutrinos, this can give rise to another flip and an absolute enhancement of the final asymmetry in the strong washout regime by up to two orders of magnitude relative to the cases either without spectators or with fully equilibrated ones. These effects are less pronounced for thermal initial conditions for the sterile neutrinos. The CP -violating source in the relativistic regime at early times is important as it is proportional to the product of lepton-number violating and lepton-number conserving rates, and therefore less suppressed than an extrapolation of the nonrelativistic approximations may suggest.

show abstract

“…where 0 is the zero-temperature decay-asymmetry defined as in Eq. (15). The source term (66e) is consistent with the calculation in Ref.…”

Section: Derivation Of the Fluid Equationssupporting

confidence: 86%

“…Ref. [15] for a recent review). In the fully relativistic regime, plasma effects such as scatterings, soft gauge boson emission, and thermal masses dominating the kinematics of one-to-two processes become important, all of which go beyond the simple description in terms of decays and inverse decays of the sterile neutrinos.…”

Section: Introductionmentioning

confidence: 99%

Relativistic and spectator effects in leptogenesis with heavy sterile neutrinos

Garbrecht

Klose

Tamarit

2020

J. High Energ. Phys.

View full text Add to dashboard Cite

show abstract

“…For a recent series of review papers on leptogenesis, see Refs. [12][13][14][15][16]. However, also the Majorana-neutrino scenario comes with a number of challenges and drawbacks.…”

Section: The Majorana-neutrino Optionmentioning

confidence: 99%

Type I seesaw mechanism as the common origin of neutrino mass, baryon asymmetry, and the electroweak scale

et al. 2019

View full text Add to dashboard Cite

The type-I seesaw represents one of the most popular extensions of the Standard Model. Previous studies of this model have mostly focused on its ability to explain neutrino oscillations as well as on the generation of the baryon asymmetry via leptogenesis. Recently, it has been pointed out that the type-I seesaw can also account for the origin of the electroweak scale due to heavy-neutrino threshold corrections to the Higgs potential. In this paper, we show for the first time that all of these features of the type-I seesaw are compatible with each other. Integrating out a set of heavy Majorana neutrinos results in small masses for the Standard Model neutrinos; baryogenesis is accomplished by resonant leptogenesis; and the Higgs mass is entirely induced by heavy-neutrino one-loop diagrams, provided that the tree-level Higgs potential satisfies scale-invariant boundary conditions in the ultraviolet. The viable parameter space is characterized by a heavy-neutrino mass scale roughly in the range 10 6.5···7.0 GeV and a mass splitting among the nearly degenerate heavy-neutrino states up to a few TeV. Our findings have interesting implications for high-energy flavor models and low-energy neutrino observables. We conclude that the type-I seesaw sector might be the root cause behind the masses and cosmological abundances of all known particles. This statement might even extend to dark matter in the presence of a keV-scale sterile neutrino.

show abstract

“…The baryon asymmetry generated by decays and inverse decays of the lightest singlet neutrino can be written as [58,59] …”

Section: A Predicting Neutrino Masses and Baryon Asymmetrymentioning

confidence: 99%

Flavor physics without flavor symmetries

Buchmüller

Patel

2018

Phys. Rev. D

View full text Add to dashboard Cite

We quantitatively analyze a quark-lepton flavor model derived from a six-dimensional supersymmetric theory with SOð10Þ × Uð1Þ gauge symmetry, compactified on an orbifold with magnetic flux. Two bulk 16-plets charged under the Uð1Þ provide the three quark-lepton generations whereas two uncharged 10-plets yield two Higgs doublets. At the orbifold fixed points mass matrices are generated with rank one or two. Moreover, the zero modes mix with heavy vectorlike split multiplets. The model possesses no flavor symmetries. Nevertheless, there exist a number of relations between Yukawa couplings, remnants of the underlying grand unified theory symmetry and the wave function profiles of the zero modes, which lead to a prediction of the light neutrino mass scale, m ν 1 ∼ 10 −3 eV and heavy Majorana neutrino masses in the range from 10 12 to 10 14 GeV. The model successfully includes thermal leptogenesis.

show abstract

Status of rates and rate equations for thermal leptogenesis

Cited by 52 publications

References 78 publications

Relativistic and spectator effects in leptogenesis with heavy sterile neutrinos

Relativistic and spectator effects in leptogenesis with heavy sterile neutrinos

Type I seesaw mechanism as the common origin of neutrino mass, baryon asymmetry, and the electroweak scale

Flavor physics without flavor symmetries

Contact Info

Product

Resources

About