Radiative seesaw model: Warm dark matter, collider signatures, and lepton flavor violating signals (original) (raw)
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Radiative seesaw: Warm dark matter, collider and lepton flavour violating signals
Physical Review D, 2009
Extending the standard model with three right-handed neutrinos (N k ) and a second Higgs doublet (η), odd under the discrete parity symmetry Z 2 , Majorana neutrino masses can be generated at 1-loop order. In the resulting model, the lightest stable particle, either a boson or a fermion, might be a dark matter candidate. Here we assume a specific mass spectrum (M 1 ≪ M 2 < M 3 < m η ) and derive its consequences for dark matter and collider phenomenology. We show that (i) the lightest right-handed neutrino is a warm dark matter particle that can give a ∼10% contribution to the dark matter density; (ii) several decay branching ratios of the charged scalar can be predicted from measured neutrino data. Especially interesting is that large lepton flavour violating rates in muon and tau final states are expected. Finally, we derive upper bounds on the right-handed neutrino Yukawa couplings from the current experimental limit on Br(µ → eγ).
Models with radiative neutrino masses and viable dark matter candidates
Journal of High Energy Physics, 2013
We provide a list of particle physics models at the TeV-scale that are compatible with neutrino masses and dark matter. In these models, the Standard Model particle content is extended with a small number (≤ 4) of scalar and fermion fields transforming as singlets, doublets or triplets under SU (2), and neutrino masses are generated radiatively via 1-loop diagrams. The dark matter candidates are stabilized by a Z 2 symmetry and are in general mixtures of the neutral components of such new multiplets. We describe the particle content of each of these models and determine the conditions under which they are consistent with current data. We find a total of 35 viable models, most of which have not been previously studied in the literature. There is a great potential to test these models at the LHC not only due to the TeV-scale masses of the new fields but also because about half of the viable models contain particles with exotic electric charges, which give rise to background-free signals. Our results should serve as a first step for detailed analysis of models that can simultaneously account for dark matter and neutrino masses.
Lepton Flavour Violation and. Dark Matter Phenomenology
2013
GENERAL INTRODUCTION AND MOTIVATIONS One of the open questions in particle physics nowadays is the so-called flavour puzzle: why there is a hierarchical structure of fermion masses and mixings, and why there are two replicas of the lightest fermions? The leptonic sector presents even more challenging features than the quark sector, where the mixings between flavour eigenstates show an approximately perturbative texture. Indeed, in the neutrino sector the values of the mixing angles appear 'randomly' distributed, and one of the mixing angles is close to maximal. On the other hand, the masses of neutrinos are believed to be below ∼ 0.3 eV, i.e. six orders of magnitude smaller than the lightest charged fermion (the electron). This should be compared with the ∼ five orders of magnitude expanded by the masses of the nine charged fermions (from the electron to the top mass), more or less equally distributed in between. Certainly, the Standard Model (SM) can be trivially extended to accommodate neutrino masses. However, the previous huge gap between the neutrinos and the rest of SM particles has posed a strong motivation to develop theoretical models that could explain it. One of the most popular theoretical frameworks to accommodate such small neutrino masses is the socalled Seesaw mechanism. The idea is that right-handed (RH) neutrinos, which are singlets under the SM gauge group, can have large Majorana masses (as they are not controlled by the electroweak-breaking scale). Then the lightest (approximately pure left-handed) neutrinos get masses suppressed by the ratio of the Higgs VEV and the right-handed Majorana mass, thus becoming extremely light. The Seesaw scenario can be easily formulated within a supersymmetric framework. Indeed, this is highly motivated by the fact that the massive right-handed neutrinos introduce large (logarithmic) corrections to the Higgs mass, which worsens the notorious Hierarchy-Problem of the Standard Model. On the other hand, the neutrino Yukawa couplings must present an off-diagonal structure (to generate the neutrino mixings), which in turn induces off-diagonal entries in the slepton matrices. The latter may potentially trigger processes which violate Lepton flavour, for example µ → eγ.
Right-handed neutrinos: Dark matter, lepton flavor violation, and leptonic collider searches
Physical Review D, 2017
We examine lepton flavor violating (LFV) interactions for heavy right-handed neutrinos that exist in most of the standard model extensions that address dark matter (DM) and neutrino mass at the loop level. In order to probe the collider effect of these LFV interactions, we impose the assumption that the model parameters give the right values of the DM relic density and fulfill the constraints from the LFV processes α → β γ and α → 3 β. We also investigate the possibility of probing these interactions, and hence the right-handed neutrino, at leptonic colliders through different final state signatures.
Decaying Warm Dark Matter and Neutrino Masses
Physical Review Letters, 2007
Neutrino masses may arise from spontaneous breaking of ungauged lepton number. Because of quantum gravity effects the associated Goldstone boson -the majoron -will pick up a mass. We determine the lifetime and mass required by cosmic microwave background observations so that the massive majoron provides the observed dark matter of the Universe. The majoron decaying dark matter (DDM) scenario fits nicely in models where neutrino masses arise a la seesaw, and may lead to other possible cosmological implications. PACS numbers: 95.35.+d, 95.36.+x, 98.65.Dx, 14.60.Pq, 14.60.St, 13.15.+g, 12.60.Fr A long-standing challenge in particle cosmology is to elucidate the nature of dark matter and its origin. A keV weakly interacting particle could provide a sizeable fraction of the critical density ρ cr = 1.88 × 10 −29 h 2 g/cm 3 and possibly play an important role in structure formation, since the associated Jeans mass lies in the relevant range [1]. Although we now know from neutrino oscillation experiments that neutrinos do have mass [2], recent cosmological data [3] as well as searches for distortions in beta [4] and double beta decay spectra [5] place a stringent limit on the absolute scale of neutrino mass that precludes neutrinos from being viable warm dark matter candidates [6] and from playing a direct role in structure formation.
Right-handed Neutrino Dark Matter with Radiative Neutrino Mass in Gauged B-L Model
2019
We study the possibility of right-handed neutrino dark matter (DM) in gauged U(1)_B-L× Z_2 extension of the standard model augmented by an additional scalar doublet, being odd under the Z_2 symmetry, to give rise to the scotogenic scenario of radiative neutrino masses. Due to lepton portal interactions, the right-handed neutrino DM can have additional co-annihilation channels apart from the usual annihilations through Z_B-L which give rise to much more allowed mass of DM from relic abundance criteria, even away from the resonance region like M_ DM≈ M_Z_B-L/2. This enlarged parameter space is found to be consistent with neutrino mass constraints while being sensitive to direct detection experiments of DM as well as rare decay experiments looking for charged lepton flavour violating decays like μ→ e γ. Due to the possibility of the Z_2 odd scalar doublet being the next to lightest stable particle that can be sufficiently produced in colliders by virtue of its gauge interactions, one c...
2016
We consider an extension of the standard model (SM) with charged singlet scalars and right handed (RH) neutrinos all at the electroweak scale. In this model, the neutrino masses are generated at three loops, which provide an explanation for their smallness, and the lightest RH neutrino, N 1 , is a dark matter candidate. We find that for three generations of RH neutrinos, the model can be consistent with the neutrino oscillation data, lepton flavor violating processes, N 1 can have a relic density in agreement with the recent Planck data, and the electroweak phase transition can be strongly first order. We also show that the charged scalars may enhance the branching ratio h → γγ, where as h → γZ get can get few percent suppression. We also discuss the phenomenological implications of the RH neutrinos at the collider.
A4-based neutrino masses with Majoron decaying dark matter
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2010
We propose an A 4 flavor-symmetric SU(3) ⊗ SU(2) ⊗ U(1) seesaw model where lepton number is broken spontaneously. A consistent two-zero texture pattern of neutrino masses and mixing emerges from the interplay of type-I and type-II seesaw contributions, with important phenomenological predictions. We show that, if the Majoron becomes massive, such seesaw scenario provides a viable candidate for decaying dark matter, consistent with cosmic microwave background lifetime constraints that follow from current WMAP observations. We also calculate the sub-leading one-loop-induced decay into photons which leads to a mono-energetic emission line that may be observed in future X-ray missions such as Xenia.
Neutrino masses, leptogenesis, and dark matter in a hybrid seesaw model
Physical Review D, 2009
We suggest a hybrid seesaw model where relatively "light" right-handed neutrinos give no contribution to the neutrino mass matrix due to a special symmetry. This allows their Yukawa couplings to the standard model particles to be relatively strong, so that the standard model Higgs boson can decay dominantly to a left and a right-handed neutrino, leaving another stable right-handed neutrino as cold dark matter. In our model neutrino masses arise via the type-II seesaw mechanism, the Higgs triplet scalars being also responsible for the generation of the matter-antimatter asymmetry via the leptogenesis mechanism.
A model for mixed warm and hot right-handed neutrino dark matter
Journal of High Energy Physics, 2021
We discuss a model where a mixed warm and hot keV neutrino dark matter rises naturally. We arrange active and sterile neutrinos in the same SU(3)L multiplet, with the lightest sterile neutrino being dark matter. The other two heavy sterile neutrinos, through their out-of-equilibrium decay, contribute both to the dilution of dark matter density and its population, after freeze-out. We show that this model features all ingredients to overcome the overproduction of keV neutrino dark matter, and explore the phenomenological implications for Big Bang Nucleosynthesis and the number of relativistic degrees of freedom.