We study the minimal type-III seesaw model in which we extend the standard model by adding two SU(2)L triplet fermions with zero hypercharge to explain the origin of the nonzero neutrino masses. We ...show that the naturalness conditions and the limits from lepton flavor violating decays provide very stringent bounds on the model parameters along with the constraints from the stability/metastability of the electroweak vacuum. We perform a detailed analysis of the model parameter space including all the constraints for both normal as well as inverted hierarchies of the light neutrino masses. We find that most of the regions that are allowed by lepton flavor violating decays and naturalness fall in the stable/metastable region depending on the values of the standard model parameters.
We consider a class of gauged U(1) extensions of the Standard Model (SM), where the light neutrino masses are generated by an inverse seesaw mechanism. In addition to the three right handed ...neutrinos, we add three singlet fermions and demand an extra Z2 symmetry under which, the third generations of both of the neutral fermions are odd, which in turn gives us a stable dark matter candidate. We express the U(1) charges of all the fermions in terms of the U(1) charges of the standard model Higgs and the new complex scalar. We study the bounds on the parameters of the model from vacuum stability, perturbative unitarity, dark matter relic density, and direct detection constraints. We also obtain the collider constraints on the Z′ mass and the U(1)′ gauge coupling. Finally, we compare all the bounds on the Z′ mass versus the U(1)′ gauge coupling plane.
We consider singlet extensions of the standard model, both in the fermion and in the scalar sector, to account for the generation of neutrino mass at the TeV scale and the existence of dark matter, ...respectively. For the neutrino sector we consider models with extra singlet fermions that can generate neutrino mass via the so-called inverse or linear seesaw mechanism, whereas a singlet scalar is introduced as the candidate for dark matter. We show that although these two sectors are disconnected at low energy, the coupling constants of both the sectors get correlated at the high-energy scale by the constraints coming from the perturbativity and stability/metastability of the electroweak vacuum. The singlet fermions try to destabilize the electroweak vacuum while the singlet scalar aids the stability. As an upshot, the electroweak vacuum may attain absolute stability even up to the Planck scale for suitable values of the parameters. We delineate the parameter space for the singlet fermion and the scalar couplings for which the electroweak vacuum remains stable/metastable and at the same time gives the correct relic density and neutrino masses and mixing angles as observed.
We study the implications of the Dark-LMA (DLMA) solution to the solar neutrino problem for neutrinoless double beta decay (0νββ). We show that, while the predictions for the effective mass governing ...0νββ remain unchanged for the inverted mass scheme, that for normal ordering becomes higher for the DLMA parameter space and moves into the "desert region" between the two. This sets a new goal for the sensitivity reach for the next-generation experiments if no signal is found for the inverted ordering by the future search programs.
We have studied the correlations among the three absolute neutrino mass observables-the effective Majorana mass (mee) which can be obtained from neutrinoless double beta decay, the electron neutrino ...mass (mβ) which is measured in single beta decay experiments, and the sum of the light neutrino masses (Σ) which is constrained from cosmological observations, in the context of minimal left-right symmetric model. Two phenomenologically interesting cases of type-I seesaw dominance as well as type-II seesaw dominance have been considered. We have taken into account the independent constraints coming from lepton flavor violation, single β decay, cosmology, and neutrinoless double beta decay and have determined the combined allowed parameter space that can be probed in the future experiments. We have also analyzed the correlations and tensions between the different mass variables. In addition, the constraints on the masses of the heavy particles coming from lepton flavor violation and the bounds on three absolute neutrino mass observables are also determined. We show that these constraints can rule out some of the parameter space which are not probed by the collider experiments.
We propose a framework to account for neutrino masses at the two-loop level. This mechanism introduces new scalars and Majorana fermions to the Standard Model. It assumes the existence of a global U ...( 1 ) × Z 2 symmetry which after partial breaking provides the stability of the dark matter candidates of the theory. The rich structure of the potential allows for the possibility of first-order phase transitions (FOPTs) in the early Universe which can lead to the generation of primordial gravitational waves. Taking into account relevant constraints from lepton flavor violation, neutrino physics, as well as the trilinear Higgs couplings at next-to-leading order accuracy, we have found a wide range of possible FOPTs which are strong enough to be probed at the proposed gravitational-wave interferometer experiments such as LISA. Published by the American Physical Society 2024
We analyze the effect of the dark large mixing angle (DLMA) solution on the effective Majorana mass ( mββ ) governing neutrinoless double beta decay (0νββ) in the presence of a sterile neutrino. We ...consider the 3 + 1 picture, comprised of one additional sterile neutrino. We check that the Mikheyev-Smirnov-Wolfenstein resonance in the Sun can take place in the DLMA parameter space in this scenario. Next, we investigate how the values of the solar mixing angle θ 12 corresponding to the DLMA region alter the predictions of mββ by including a sterile neutrino in the analysis. We also compare our results with three-generation cases for both standard large mixing angle (LMA) and DLMA. Additionally, we evaluate the discovery sensitivity of the future 136Xe experiments in this context.
Linear seesaw mechanism from dark sector Hernández, A. E. Cárcamo; Vishnudath, K. N.; Valle, José W. F.
The journal of high energy physics,
09/2023, Letnik:
2023, Številka:
9
Journal Article
Recenzirano
Odprti dostop
A
bstract
We propose a minimal model where a dark sector seeds neutrino mass generation radiatively within the linear seesaw mechanism. Neutrino masses are calculable, since tree-level contributions ...are forbidden by symmetry. They arise from spontaneous lepton number violation by a small Higgs triplet vacuum expectation value. Lepton flavour violating processes e.g.
μ
→
eγ
can be sizeable, despite the tiny neutrino masses. We comment also on dark-matter and collider implications.
We consider a general, anomaly free U(1)′ extension of the Standard Model (SM) where the neutrino mass is generated at the tree level via the inverse seesaw mechanism. The model contains three right ...handed neutrinos, three additional singlet fermions, one extra complex scalar and a neutral gauge boson (Z′). Instead of resorting to a specific U(1) extension, we consider a class of models by taking the U(1)′ charges of the scalars to be free parameters. Here, we assign one pair of the pseudo-Dirac degenerate sterile neutrinos as Dark Matter (DM) candidates which are produced by the freeze-in mechanism. Considering different mass regimes of the DM, Z′ and reheating temperature, we obtain constraints on the U(1)′ charges giving the correct relic abundance. We have also obtained constraints on Z′ mass and coupling from consideration of relic density as well as high energy collider experiments like ATLAS in case of heavy Z′ or in intensity and lifetime frontier experiments like DUNE, FASERs, and ILC beam dump which are looking for light Z′. Additionally, in this model, the decay of pseudo-Dirac DM into active neutrinos can explain the 511 keV line observed by the INTEGRAL satellite.
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