2,878 research outputs found
Beyond the Standard Model with leptogenesis and neutrino data
In this short review I discuss how high energy (type I) seesaw models can be
nicely embedded within grand-unified models and reproduce the observed
matter-antimatter asymmetry with leptogenesis. In particular, after discussing
general features and results in leptogenesis,
I focus on -inspired leptogenesis and on a particular solution, the
strong thermal -inspired solution, that provides an interesting way to
understand neutrino mixing parameters: the non-vanishing reactor mixing angle,
the emerging negative sign of and the slight hints favouring
normally ordered neutrino masses and an atmospheric mixing angle in the first
octant. I also briefly discuss leptogenesis within two right-handed seesaw
neutrino models. In this case a a third decoupled right-handed neutrino can
provide a candidate for very heavy cold decaying dark matter produced from
right-handed neutrino mixing with a mass in the TeV-EeV range and its decays
would give a contribution to the IceCube high energy neutrino events in
addition to an astrophysical component.Comment: 12 pages, 2 Figures; compendium of plenary talks given at Neutrino
2016, NuFact 2016 and IPA 2016; v2: Ref.'s adde
Flavor effects in thermal leptogenesis
We review recent developments in leptogenesis on flavor effects. Their
account discloses an important connection between the matter-antimatter
asymmetry of the Universe and CP violation at low energies. Besides, they
modify the upper bound on the neutrino masses holding in the unflavored case.
In this respect, it is important to identify the exact condition for flavor
effects to be relevant and for the `fully flavored' Boltzmann equations to be
valid.Comment: 3 pages, no figure ; contribution to the proceedings of NOW 2006,
Conca Specchiulla, Sep. 9-16, 200
The minimal scenario of leptogenesis
We review the main features and results of thermal leptogenesis within the
type I seesaw mechanism, the minimal extension of the Standard Model explaining
neutrino masses and mixing. After presenting the simplest approach, the vanilla
scenario, we discuss various important developments in recent years, such as
the inclusion of lepton and heavy neutrino flavour effects, a description
beyond a hierarchical heavy neutrino mass spectrum and an improved kinetic
description within the density matrix and the closed-time-path formalisms. We
also discuss how leptogenesis can ultimately represent an important
phenomenological tool to test the seesaw mechanism and the underlying model of
new physics.Comment: 37 pages, 4 figures; invited review chapter for the "Focus on the
Origin of Matter" issue published in the New Journal of Physic
SO(10)-inspired solution to the problem of the initial conditions in leptogenesis
We show that, within SO(10)-inspired leptogenesis, there exists a solution,
with definite constraints on low energy neutrino parameters, able
simultaneously to reproduce the observed baryon asymmetry and to satisfy the
conditions for the independence of the final asymmetry of the initial
conditions (strong thermal leptogenesis). We find that the wash-out of a
pre-existing asymmetry as large as O(0.1) requires: i) reactor mixing angle in
the range \theta_13 = (2 - 20) degrees, in agreement with the experimental
result \theta_13 = (8 - 10) degrees; ii) atmospheric mixing angle in the range
\theta_23 = (16 - 41) degrees, compatible only with current lowest
experimentally allowed values; iii) Dirac phase in the range \delta \simeq
-\pi/2 - \pi/5, with the bulk of the solutions around \delta \simeq -\pi/5 and
such that sign(J_CP)= - sign(\eta_B); iv) neutrino masses m_i normally ordered;
v) lightest neutrino mass in the range m_1 \simeq (15 - 25) meV, corresponding
to \sum_i m_i \simeq (85 - 105) meV; vi) neutrinoless double beta decay
(0\nu\beta\beta) effective neutrino mass m_ee \simeq 0.8 m_1. All together this
set of predictive constraints characterises the solution quite distinctively,
representing a difficultly forgeable, fully testable, signature. In particular,
the condition m_ee \simeq 0.8 m_1 \simeq 15 meV can be tested by cosmological
observations and (ultimately) by 0\nu\beta\beta experiments. We also discuss
different aspects such as theoretical uncertainties, stability under variation
of the involved parameters, form of the orthogonal and RH neutrino mixing
matrices.Comment: 44 pages, 8 figures; v3: typos corrected, matches NPB versio
Supersymmetric -inspired leptogenesis and a new -dominated scenario
We study the supersymmetric extension of -inspired thermal
leptogenesis showing the constraints on neutrino parameters and on the reheat
temperature that derive from the condition of successful
leptogenesis from next-to-lightest right handed (RH) neutrinos () decays
and the more stringent ones when independence of the initial conditions (strong
thermal leptogenesis) is superimposed. In the latter case, the increase of the
lightest right-handed neutrino () decay parameters helps the wash-out of a
pre-existing asymmetry and constraints relax compared to the non-supersymmetric
case. We find significant changes especially in the case of large
values . In particular, for normal ordering, the atmospheric
mixing angle can now be also maximal. The lightest (ordinary) neutrino mass is
still constrained within the range
(corresponding to ). Inverted
ordering is still disfavoured, but an allowed region satisfying strong thermal
leptogenesis opens up at large values. We also study in detail the
lower bound on finding independently of the initial abundance. Finally, we propose a new
-dominated scenario where the mass is lower than the sphaleron
freeze-out temperature. In this case there is no wash-out and we find
. These results indicate that
-inspired thermal leptogenesis can be made compatible with the upper
bound from the gravitino problem, an important result in light of the role
often played by supersymmetry in the quest of a realistic model of fermion
masses.Comment: 35 pages, 10 figures; v3: matches JCAP versio
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