scholarly journals Relaxing cosmological neutrino mass bounds with unstable neutrinos

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Miguel Escudero ◽  
Jacobo Lopez-Pavon ◽  
Nuria Rius ◽  
Stefan Sandner
Keyword(s):  
Neutrino Mass ◽  
Particle Physics ◽  
Goldstone Boson ◽  
Mass Scale ◽  
Simple Extension ◽  
Type I ◽  
Mass Generation ◽  
Age Of The Universe ◽  
Neutrino Mass Models ◽  
The Right

Abstract At present, cosmological observations set the most stringent bound on the neutrino mass scale. Within the standard cosmological model (ΛCDM), the Planck collaboration reports ∑mv< 0.12 eV at 95 % CL. This bound, taken at face value, excludes many neutrino mass models. However, unstable neutrinos, with lifetimes shorter than the age of the universe τν ≲ tU, represent a particle physics avenue to relax this constraint. Motivated by this fact, we present a taxonomy of neutrino decay modes, categorizing them in terms of particle content and final decay products. Taking into account the relevant phenomenological bounds, our analysis shows that 2-body decaying neutrinos into BSM particles are a promising option to relax cosmological neutrino mass bounds. We then build a simple extension of the type I seesaw scenario by adding one sterile state ν4 and a Goldstone boson ϕ, in which νi→ ν4ϕ decays can loosen the neutrino mass bounds up to ∑mv ∼ 1 eV, without spoiling the light neutrino mass generation mechanism. Remarkably, this is possible for a large range of the right-handed neutrino masses, from the electroweak up to the GUT scale. We successfully implement this idea in the context of minimal neutrino mass models based on a U(1)μ−τ flavor symmetry, which are otherwise in tension with the current bound on ∑mv.

scholarly journals The hubble tension as a hint of leptogenesis and neutrino mass generation

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Miguel Escudero ◽  
Samuel J. Witte
Keyword(s):  
Neutrino Mass ◽  
Goldstone Boson ◽  
Predictive Distribution ◽  
Mass Generation ◽  
Posterior Predictive Distribution ◽  
Additional Energy ◽  
Dark Radiation ◽  
Neutrino Mass Generation ◽  
Neutrino Mass Models ◽  
The Universe

AbstractThe majoron, a neutrinophilic pseudo-Goldstone boson conventionally arising in the context of neutrino mass models, can damp neutrino free-streaming and inject additional energy density into neutrinos prior to recombination. The combination of these effects for an eV-scale mass majoron has been shown to ameliorate the outstanding $$H_0$$ H 0 tension, however only if one introduces additional dark radiation at the level of $$\Delta N_{\mathrm{eff}} \sim 0.5$$ Δ N eff ∼ 0.5 . We show here that models of low-scale leptogenesis can naturally source this dark radiation by generating a primordial population of majorons from the decays of GeV-scale sterile neutrinos in the early Universe. Using a posterior predictive distribution conditioned on Planck2018+BAO data, we show that the value of $$H_0$$ H 0 observed by the SH$$_0$$ 0 ES collaboration is expected to occur at the level of $$\sim 10\%$$ ∼ 10 % in the primordial majoron cosmology (to be compared with $$\sim 0.1\%$$ ∼ 0.1 % in the case of $$\Lambda $$ Λ CDM). This insight provides an intriguing connection between the neutrino mass mechanism, the baryon asymmetry of the Universe, and the discrepant measurements of $$H_0$$ H 0 .

scholarly journals Observable proton decay in flipped SU(5)

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Maria Mehmood ◽  
Mansoor Ur Rehman ◽  
Qaisar Shafi
Keyword(s):  
Neutrino Mass ◽  
Gauge Coupling ◽  
Proton Decay ◽  
Type I ◽  
Mass Model ◽  
Intermediate Scale ◽  
Decay Channels ◽  
Proton Lifetime ◽  
Hybrid Inflation ◽  
Neutrino Mass Models

Abstract We explore proton decay in a class of realistic supersymmetric flipped SU(5) models supplemented by a U(1)R symmetry which plays an essential role in implementing hybrid inflation. Two distinct neutrino mass models, based on inverse seesaw and type I seesaw, are identified, with the latter arising from the breaking of U(1)R by nonrenormalizable superpotential terms. Depending on the neutrino mass model an appropriate set of intermediate scale color triplets from the Higgs superfields play a key role in proton decay channels that include p → (e+, μ+) π0, p → (e+, μ+) K0, p →$$ \overline{v}{\pi}^{+} $$ v ¯ π + , and p →$$ \overline{v}{K}^{+} $$ v ¯ K + . We identify regions of the parameter space that yield proton lifetime estimates which are testable at Hyper-Kamiokande and other next generation experiments. We discuss how gauge coupling unification in the presence of intermediate scale particles is realized, and a Z4 symmetry is utilized to show how such intermediate scales can arise in flipped SU(5). Finally, we compare our predictions for proton decay with previous work based on SU(5) and flipped SU(5).

scholarly journals Exploding operators for Majorana neutrino masses and beyond

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
John Gargalionis ◽  
Raymond R. Volkas
Keyword(s):  
Neutrino Mass ◽  
Model Building ◽  
Dominant Role ◽  
New Physics ◽  
Majorana Neutrino ◽  
Effective Field ◽  
Tree Level ◽  
Mass Generation ◽  
Neutrino Mass Models ◽  
Almost All

Abstract Building UV completions of lepton-number-violating effective operators has proved to be a useful way of studying and classifying models of Majorana neutrino mass. In this paper we describe and implement an algorithm that systematises this model-building procedure. We use the algorithm to generate computational representations of all of the tree-level completions of the operators up to and including mass-dimension 11. Almost all of these correspond to models of radiative neutrino mass. Our work includes operators involving derivatives, updated estimates for the bounds on the new-physics scale associated with each operator, an analysis of various features of the models, and a look at some examples. We find that a number of operators do not admit any completions not also generating lower-dimensional operators or larger contributions to the neutrino mass, ruling them out as playing a dominant role in the neutrino-mass generation. Additionally, we show that there are at most five models containing three or fewer exotic multiplets that predict new physics that must lie below 100 TeV. Accompanying this work we also make available a searchable database containing all of our results and the code used to find the completions. We emphasise that our methods extend beyond the study of neutrino-mass models, and may be useful for generating completions of high-dimensional operators in other effective field theories. Example code: ref. [37].

scholarly journals Flavour effects in gravitational leptogenesis

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Rome Samanta ◽  
Satyabrata Datta
Keyword(s):  
Mass Spectrum ◽  
Chemical Potential ◽  
Mass Scale ◽  
Lepton Number ◽  
Type I ◽  
Lepton Asymmetry ◽  
Seesaw Mechanism ◽  
Set Up ◽  
The Right ◽  
Lepton Number Violating

Abstract Within the Type-I seesaw mechanism, quantum effects of the right-handed (RH) neutrinos in the gravitational background lead to an asymmetric propagation of lepton and anti-leptons which induces a Ricci scalar and neutrino Dirac-Yukawa coupling dependent chemical potential and therefore a lepton asymmetry in equilibrium. At high temperature, lepton number violating scattering processes try to maintain a dynamically generated lepton asymmetry in equilibrium. However, when the temperature drops down, the interactions become weaker, and the asymmetry freezes out. The frozen out asymmetry can act as a pre-existing asymmetry prior to the standard Fukugita-Yanagida leptogenesis phase (Ti ∼ Mi, where Mi is the mass of ith RH neutrino). It is then natural to consider the viability of gravitational leptogenesis for a given RH mass spectrum which is not consistent with successful leptogenesis from decays. Primary threat to this gravity-induced lepton asymmetry to be able to successfully reproduce the observed baryon-to-photon ratio is the lepton number violating washout processes at Ti ∼ Mi. In a minimal seesaw set up with two RH neutrinos, these washout processes are strong enough to erase a pre-existing asymmetry of significant magnitude. We show that when effects of flavour on the washout processes are taken into account, the mechanism opens up the possibility of successful leptogenesis (gravitational) for a mass spectrum M2 » 109GeV » M1 with M1 ≳ 6.3 × 106 GeV. We then briefly discuss how, in general, the mechanism leaves its imprints on the low energy CP phases and absolute light neutrino mass scale.

scholarly journals Investigating two heavy neutral leptons neutrino seesaw mechanism at SHiP

2019 ◽  
Vol 34 (08) ◽  
pp. 1950047
Author(s):  
Marco Chianese ◽  
Damiano F. G. Fiorillo ◽  
Gennaro Miele ◽  
Stefano Morisi
Keyword(s):  
Neutrino Mass ◽  
Double Beta Decay ◽  
Type I ◽  
Mass Generation ◽  
Seesaw Mechanism ◽  
Mixing Angle ◽  
Mechanism Model ◽  
Neutrino Mass Generation ◽  
Generation Mechanisms ◽  
The Masses

One of the main purposes of SHiP experiment is to shed light on neutrino mass generation mechanisms like the so-called seesaw. We consider a minimal type-I seesaw neutrino mass mechanism model with two heavy neutral leptons (right-handed or sterile neutrinos) with arbitrary masses. Extremely high active-sterile mixing angle requires a correlation between the phases of the Dirac neutrino couplings. Actual experimental limits on the half-life of neutrinoless double beta decay [Formula: see text]-rate on the active-sterile mixing angle are not significative in constraining the masses or the mixing measurable by SHiP.

scholarly journals TRIBIMAXIMAL MIXING IN NEUTRINO MASS MATRICES WITH TEXTURE ZEROS OR VANISHING MINORS

2011 ◽  
Vol 26 (07) ◽  
pp. 501-514 ◽  
Author(s):  
S. DEV ◽  
SHIVANI GUPTA ◽  
RADHA RAMAN GAUTAM
Keyword(s):  
Neutrino Mass ◽  
Mass Matrix ◽  
Mass Scale ◽  
Neutrino Mass Matrix ◽  
Seesaw Mechanism ◽  
Majorana Mass ◽  
Absolute Mass ◽  
Mass Matrices ◽  
The One ◽  
The Right

We study the existence of one/two texture zeros or one/two vanishing minors in the neutrino mass matrix with μτ symmetry. In the basis where the charged lepton mass matrix and the Dirac neutrino mass matrix are diagonal, the one/two zeros or one/two vanishing minors on the right-handed Majorana mass matrix having μτ symmetry will propagate via seesaw mechanism as one/two vanishing minors or one/two texture zeros in the neutrino mass matrix with μτ symmetry respectively. It is found that only five such texture structures of the neutrino mass matrix are phenomenologically viable. For tribimaximal mixing, these texture structures reduce the number of free parameters to one. Interesting predictions are obtained for the effective Majorana mass Mee, the absolute mass scale and the Majorana-type CP violating phases.

scholarly journals The Nature of Massive Neutrinos

2013 ◽  
Vol 2013 ◽  
pp. 1-20 ◽  
Author(s):  
S. T. Petcov
Keyword(s):  
Neutrino Mass ◽  
Current Data ◽  
Future Research ◽  
Type I ◽  
Neutrino Mixing ◽  
Mass Generation ◽  
Triplet Model ◽  
Majorana Neutrinos ◽  
Massive Neutrinos ◽  
Neutrino Mass Generation

The compelling experimental evidences for oscillations of solar, reactor, atmospheric, and accelerator neutrinos imply the existence of 3-neutrino mixing in the weak charged lepton current. The current data on the 3-neutrino mixing parameters are summarised and the phenomenology of 3-νmixing is reviewed. The properties of massive Majorana neutrinos and of their various possible couplings are discussed in detail. Two models of neutrino mass generation with massive Majorana neutrinos—the type I see-saw and the Higgs triplet model—are briefly reviewed. The problem of determining the nature, Dirac or Majorana, of massive neutrinos is considered. The predictions for the effective Majorana mass|〈m〉|in neutrinoless double-beta-((ββ)0ν-) decay in the case of 3-neutrino mixing and massive Majorana neutrinos are summarised. The physics potential of the experiments, searching for(ββ)0ν-decay for providing information on the type of the neutrino mass spectrum, on the absolute scale of neutrino masses, and on the Majorana CP-violation phases in the PMNS neutrino mixing matrix, is also briefly discussed. The opened questions and the main goals of future research in the field of neutrino physics are outlined.

scholarly journals High Scale Type-II Seesaw, Dominant Double Beta Decay within Cosmological Bound and LFV Decays in SU(‎5)

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
M. K. Parida ◽  
Rajesh Satpathy
Keyword(s):  
Beta Decay ◽  
Neutrino Mass ◽  
Double Beta Decay ◽  
Type I ◽  
Mass Hierarchy ◽  
Type Ii ◽  
Inverted Hierarchy ◽  
Mass Generation ◽  
Neutrino Mass Generation ◽  
Physical Phenomena

Very recently novel implementation of type-II seesaw mechanism for neutrino mass has been proposed in SU(5) grand unified theory with a number of desirable new physical phenomena beyond the standard model. Introducing heavy right-handed neutrinos and extra fermion singlets, in this work we show how the type-I seesaw cancellation mechanism works in this SU(5) framework. Besides predicting verifiable LFV decays, we further show that the model predicts dominant double beta decay with normal hierarchy or inverted hierarchy of active light neutrino masses in concordance with cosmological bound. In addition a novel right-handed neutrino mass generation mechanism, independent of type-II seesaw predicted mass hierarchy, is suggested in this work.

scholarly journals Resonant enhancement in leptogenesis

2018 ◽  
Vol 33 (05n06) ◽  
pp. 1842003 ◽  
Author(s):  
P. S. B. Dev ◽  
M. Garny ◽  
J. Klaric ◽  
P. Millington ◽  
D. Teresi
Keyword(s):  
Lower Bound ◽  
Mass Difference ◽  
Decisive Role ◽  
Mass Scale ◽  
Type I ◽  
Cp Asymmetry ◽  
Resonant Enhancement ◽  
Majorana Neutrinos ◽  
The Right ◽  
Decay Asymmetry

Vanilla leptogenesis within the type I seesaw framework requires the mass scale of the right-handed neutrinos to be above [Formula: see text] GeV. This lower bound can be avoided if at least two of the sterile states are almost mass degenerate, which leads to an enhancement of the decay asymmetry. Leptogenesis models that can be tested in current and upcoming experiments often rely on this resonant enhancement, and a systematic and consistent description is therefore necessary for phenomenological applications. In this paper, we give an overview of different methods that have been used to study the saturation of the resonant enhancement when the mass difference becomes comparable to the characteristic width of the Majorana neutrinos. In this limit, coherent flavor transitions start to play a decisive role, and off-diagonal correlations in flavor space have to be taken into account. We compare various formalisms that have been used to describe the resonant regime and discuss under which circumstances the resonant enhancement can be captured by simplified expressions for the CP asymmetry. Finally, we briefly review some of the phenomenological aspects of resonant leptogenesis.

scholarly journals RIGHT-HANDED MAJORANA NEUTRINO MASS MATRICES FOR GENERATING BIMAXIMAL MIXINGS IN DEGENERATE AND INVERTED MODELS OF NEUTRINOS

2003 ◽  
Vol 18 (05) ◽  
pp. 743-753 ◽  
Author(s):  
MAHADEV PATGIRI ◽  
N. NIMAI SINGH
Keyword(s):  
Neutrino Mass ◽  
Atmospheric Neutrino ◽  
Majorana Neutrino ◽  
Double Beta Decay ◽  
Diagonal Form ◽  
Left Handed ◽  
Mass Matrices ◽  
Neutrino Mass Models ◽  
The Right ◽  
Majorana Neutrino Mass

An attempt is made to generate the bimaximal mixings of the three species of neutrinos from the textures of the right-handed Majorana neutrino mass matrices. We extend our earlier work in this paper for the generation of the nearly degenerate as well as the inverted hierarchical models of the left-handed Majorana neutrino mass matrices using the non-diagonal textures of the right-handed Majorana neutrino mass matrices and the diagonal form of Dirac neutrino mass matrices, within the framework of the see-saw mechanism in a model independent way. Such Majorana neutrino mass models are important in explaining the recently reported result on the neutrinoless double beta decay (0νββ) experiment, together with the earlier established data on LMA MSW solar and atmospheric neutrino oscillations.

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