Related papers: Tree-level unitarity constraints on heavy neutral …
Heavy neutral leptons (HNLs) are often among the hypothetical ingredients behind nonzero neutrino masses. If sufficiently light, they can be produced and detected in fixed-target-like experiments. We show that if the HNLs belong to a richer…
The existence of right-handed neutrinos, or heavy neutral leptons (HNLs), is strongly motivated by the observation of neutrino masses and mixing. The mass of these new particles could lie below the electroweak scale, making them accessible…
We study the models with the Majorana neutrino masses generated radiatively by two-loop diagrams due to the Yukawa $\rho \bar \ell_R^c \ell_R$ and effective $\rho^{\pm\pm} W^\mp W^\mp$ couplings along with a scalar triplet $\Delta$, where…
If the observed light neutrino masses are induced by their Yukawa couplings to singlet right-handed neutrinos, natural smallness of those renders direct collider tests of the electroweak scale neutrino mass mechanisms almost impossible both…
Heavy Neutral Leptons (HNLs) are strongly motivated by theory due to their capability of simultaneously explaining the observed phenomena of dark matter, neutrino oscillations and the baryon asymmetry of the Universe. The existence of such…
Heavy Neutral Leptons (HNLs) with masses $\mathcal{O}(0.1 - 1\,\,\text{GeV}/c^{2})$ are promising candidates for the simultaneous explanation of the smallness of the observed neutrino masses as well as the matter-antimatter asymmetry in the…
We present a model of radiative neutrino masses which also resolves anomalies reported in $B$-meson decays, $R_{D^{(\star)}}$ and $R_{K^{(\star)}}$, as well as in muon $g-2$ measurement, $\Delta a_\mu$. Neutrino masses arise in the model…
We propose a model-independent framework to classify and study neutrino mass models and their phenomenology. The idea is to introduce one particle beyond the Standard Model which couples to leptons and carries lepton number together with an…
We investigate the tree-level neutrino mass generation in the gauged $U(1)_\ell$ lepton model recently proposed by us [arXiv:1805.10382]. With the addition of one Standard Model(SM) singlet, $\phi_1(Y=0, \ell=1)$, and one SM triplet scalar,…
Heavy neutrinos with masses below the electroweak scale can simultaneously generate the light neutrino masses via the seesaw mechanism and the baryon asymmetry of the universe via leptogenesis. The requirement to explain these phenomena…
In a recent paper, we showed that tree level up-down unification of fermion Yukawa couplings is a natural consequence of a large class of supersymmetric models. They can lead to viable quark masses and mixings for moderately large values of…
The arbitrariness of Yukawa couplings can be reduced by the imposition of some flavor symmetries and/or by the realization of texture zeros. We review neutrino Yukawa textures with zeros within the framework of the type-I seesaw with three…
We study the non-Hermitian extension of the Lagrangian of the Standard Model extended by singlet right-handed heavy neutrinos. The Yukawa coupling matrices comprise of hermitian and non-hermitian components and the neutrino mass eigenvalues…
A plausible explanation for the lightness of neutrino masses is that neutrinos are massless at tree level, with their mass (typically Majorana) being generated radiatively at one or more loops. The new couplings, together with the…
We analyze the neutrino Yukawa matrix by considering three constraints: the out-of-equilibrium condition of lepton number violating process responsible for leptogenesis, the upper bound of branching ratio of lepton flavor violating decay,…
For type I seesaw and in the basis where the charged lepton and heavy right-handed neutrino mass matrices are real and diagonal, four has been shown to be the maximum number of zeros allowed in the neutrino Yukawa coupling matrix $Y_\nu$.…
We review and update the current phenomenological constraints on minimal type I seesaw extensions of the Standard Model in which New Physics content can be probed at the electroweak scale. In this class of models, the flavour structure of…
Electroweak Baryogenesis, given a first order phase transition, does not work in the standard model because the quark Yukawa matrices are too hierarchical. On the other hand, the neutrino mass matrix is apparently not hierarchical. In…
We make a simple ansatz for the supersymmetric lepton-number violating Yukawa couplings, by relating them to the corresponding Higgs Yukawa couplings. This reduces the free B$_3$ parameters from 36 to 6. We fit these parameters to solve the…
We consider a version of the low-scale type I seesaw mechanism for generating small neutrino masses, as an alternative to the standard seesaw scenario. It involves two right-handed (RH) neutrinos $\nu_{1R}$ and $\nu_{2R}$ having a Majorana…