Related papers: Seesaw Neutrinos from the Heterotic String
The three electroweak doublet neutrinos $\nu_{e,\mu,\tau}$ of the Standard Model may acquire small seesaw masses, using either three Majorana fermion singlets $N$ or three Majorana fermion triplets $(\Sigma^+,\Sigma^0,\Sigma^-)$. It is…
The see-saw mechanism of neutrino mass generation may enhance lepton mixing up to maximal even if the Dirac mass matrices of leptons have structure similar to that in the quark sector. Two sets of conditions for such an enhancement are…
The recently proposed "mini-seesaw mechanism" combines naturally suppressed Dirac and Majorana masses to achieve light Standard Model neutrinos via a low-scale seesaw. A key feature of this approach is the presence of multiple light (order…
Heavy right-handed neutrinos are highly motivated due to their connection with the origin of neutrino masses via the seesaw mechanism. If the right-handed neutrino Majorana mass is at or below the weak scale, direct experimental discovery…
We consider various possibilities for generating neutrino masses in supersymmetric models with an additional U(1)' gauge symmetry. One class of models involves two extra U(1)' x U(1)'' gauge symmetries, with U(1)'' breaking at an…
In this paper we consider possible mechanisms to generate small Majorana neutrino masses for active neutrinos in the scenario of gauge-Higgs unification, a candidate for physics beyond the standard model. We stress that it is non-trivial to…
A new lefthanded see-saw mechanism is constructed, implying both the smallness of active-neutrino masses and decoupling of heavy passive neutrinos, similarly to the situation in the case of conventional see-saw. But now, in place of the…
The problem of neutrino masses and mixing angles is analysed in a class of supersymmetric grand unified models, with SO(10) gauge symmetry and global U(2) flavour symmetry. Adopting the seesaw mechanism for the generation of the neutrino…
In the framework of the seesaw mechanism, and adopting a typical form for the Dirac neutrino mass matrix, we discuss the impact of minimal forms of the Majorana neutrino mass matrix. These matrices contain four or three texture zeros and…
In the framework of the seesaw mechanism with three heavy right-handed Majorana neutrinos and no Higgs triplets we carry out a systematic study of the structure of the right-handed neutrino sector. Using the current low-energy neutrino data…
The seesaw mechanism explains the exclusive smallness of neutrino masses by the presence of very heavy Majorana masses and leads to the appearance of Majorana particles and to the direct lepton number violation. The author proposes a seesaw…
The seesaw mechanism provides a simple explanation for the lightness of the known neutrinos. Under the standard assumption of a weak scale Dirac mass and a heavy sterile Majorana scale the neutrino mass is naturally suppressed below the…
We investigate a simple model of neutrino mass based on SU(3)_C X SU(3)_L X U(1)_X gauge unification. The Yukawa coupling of the model has automatic lepton-number symmetry which is broken only by the self-couplings of the Higgs boson. At…
In the framework of SO(10) gauge unification and the seesaw mechanism, we show that the upper bound on the mass of the heaviest right-handed neutrino $M_{R_3} < 3 \times 10^{11}$ GeV, given by the Pati-Salam intermediate scale of $B-L$…
We discuss the implications of large neutrino mixings for grand unified theories based on the seesaw mechanism. In SU(5) GUTs large mixings can be accomodated by means of $U(1)_F$ flavour symmetries. In these models the heavy Majorana…
In the framework of a minimal extension of the SM, where the only additional fields are three right-handed neutrinos, we suggest that the charged lepton, the Dirac neutrino and the right-handed Majorana neutrino mass matrices are all, to…
If neutrino masses are produced by a see-saw mechanism the Standard Model prediction for the Higgs mass window (defined by upper (perturbativity) and lower (stability) bounds) can be substantially affected. Actually the Higgs mass window…
In the extension of the standard model with one right-handed neutrino and one Higgs triplet, we propose a suppression mechanism, obtaining small masses for the active neutrinos, while mixing angles are predicted with a right-handed neutrino…
A minimal extension of the Standard Model is proposed, where the observed left-handed neutrinos obtain naturally small Majorana masses from a one-loop radiative seesaw mechanism. This model has two candidates (one bosonic and one fermionic)…
It is found that the seesaw mechanism not only explain the smallness of neutrino masses but also account for the large mixing angles simultaneously, even if the unification of the neutrino Dirac mass matrix with that of up-type quark sector…