Abstract:
We dynamically realize the supersymmetric inverse seesaw mechanism in the next to the minimal supersymmetic standard model (NMSSM) in a minimal form. The crucial observation is that the inclusion of a dimension-five operator \bar N^2S^2/M_*, which violates lepton number and is suppressed by the fundamental scale M_*, can readily produce a light neutrino mass scale m_\nu \sim 0.01$ eV. This model is protected by Z_4^R\times Z_2^M discrete symmetry and a very predictive parameter space is restricted by the requirement of naturalness. Then we study some interesting phenomenological consequencese: (i) A light sneutrino (\sim 8 GeV), which is the lightest supersymmetric particle (LSP) and then the dark matter candidate, can elegantly explain the DAMA/CoGeNT results and even account for the FERMI-LAT gamma ray signals; (ii) It is possible that the sneutrino is an asymmetric dark matter and thus the \Omega_{DM}:\Omega_b\approx 5:1 naturally predicts a light dark matter; (iii) Higgs physics maybe dramatically changed due to the significant coupling y_NLH_uN and the light sneutrinos out of the inverse seesaw sector, consequently the lightest Higgs boson is likely dominantly decay to a pair of light sneutrinos. In the DAMA/CoGeNT region, the Higgs typically decays to a pair of LSPs with branching ratio >90%

Abstract:
We consider the possibility of simultaneously addressing the dark matter problem and neutrino mass generation in the minimal inverse seesaw realisation. The Standard Model is extended by two right-handed neutrinos and three sterile fermionic states, leading to three light active neutrino mass eigenstates, two pairs of (heavy) pseudo-Dirac mass eigenstates and one (mostly) sterile state with mass around the keV, possibly providing a dark matter candidate, and accounting for the recently observed and still unidentified monochromatic 3.5 keV line in galaxy cluster spectra. The conventional production mechanism through oscillation from active neutrinos can account only for $\sim 43\%$ of the observed relic density. This can be slightly increased to $\sim 48\%$ when including effects of entropy injection from the decay of light (with mass below 20 GeV) pseudo-Dirac neutrinos. The correct relic density can be achieved through freeze-in from the decay of heavy (above the Higgs mass) pseudo-Dirac neutrinos. This production is only effective for a limited range of masses, such that the decay occurs not too far from the electroweak phase transition. We thus propose a simple extension of the inverse seesaw framework, with an extra scalar singlet coupling to both the Higgs and the sterile neutrinos, which allows to achieve the correct dark matter abundance in a broader region of the parameter space, in particular in the low mass region for the pseudo-Dirac neutrinos.

Abstract:
A Dirac fermion carrying an integral weak isospin and the vanishing hypercharge is considered as its neutral component can be a promising dark matter candidate (called the minimal dark matter) whose mass is of order 100 GeV. While the symmetric population annihilates away due to a rapid gauge interaction, its asymmetric abundance is supposed to be produced by the decay of a right-handed neutrino superfield in the supersymmetric type I seesaw mechanism. The efficiencies for generating the dark matter and lepton asymmetries are calculated by solving a set of approximate Boltzmann equations. A spectacular feature of this scenario is the existence of a long-lived singly- or multiply-charged scalar and a shorter-lived singly-charged fermion whose tracks can be readily looked for at the LHC.

Abstract:
We show that when the supersymmetric SU(5) model is extended to explain small neutrino masses by the type III seesaw mechanism, the new {\bf 24}-dimensional fields needed for the purpose can act as messengers for transmitting SUSY breaking from a hidden sector to the visible sector. For the three {\bf 24} case, the constraints of grand unification and suppressed lepton flavor violation restrict the seesaw scale in this case to be in the narrow range of $10^{12}-10^{13}$ GeV. The model predicts (i) a stable LSP gravitino with mass in the range of 1-10 MeV which can be a cold dark matter of the universe; (ii) a stau NLSP which is detectable at LHC; (iii) a lower bound on the branching ratio $BR(\mu \to e \gamma)$ larger than $10^{-14}$ testable by the ongoing MEG experiment as well as characteristic particle spectrum different from other SUSY breaking scenarios. We also discuss the case with two {\bf 24} fields, which is the minimal case that can explain neutrino oscillation data.

Abstract:
The seesaw mechanism in models with extra dimensions is shown to be generically consistent with a broad range of Majorana masses. The resulting democracy of scales implies that the seesaw mechanism can naturally explain the smallness of neutrino masses for an arbitrarily small right-handed neutrino mass. If the scales of the seesaw parameters are split, with two right-handed neutrinos at a high scale and one at a keV scale, one can explain the matter-antimatter asymmetry of the universe, as well as dark matter. The dark matter candidate, a sterile right-handed neutrino with mass of several keV, can account for the observed pulsar velocities and for the recent data from Chandra X-ray Observatory, which suggest the existence of a 5 keV sterile right-handed neutrino.

Abstract:
We consider supersymmetric models in which the right-handed sneutrino is a viable WIMP dark matter candidate. These are either simple extensions of the Minimal Supersymmetric Standard Model or models with the addition of an extra U(1) group. All of them can explain small neutrino masses, through either the Inverse or the Linear Seesaw mechanism. We investigate the properties of the dark matter candidate naturally arising in these scenarios. We check for phenomenological bounds, such as correct relic abundance, consistency with direct detection cross section limits and laboratory constraints. Especially, we comment on limitations of the model space due to lepton flavour violating charged lepton decays.

Abstract:
Seesaw mechanism provides a natural explanation of light neutrino masses through suppression of heavy seesaw scale. In inverse seesaw models the seesaw scale can be much lower than that in the usual seesaw models. If terms inducing seesaw masses are further induced by loop corrections, the seesaw scale can be lowered to be in the range probed by experiments at the LHC without fine tuning. In this paper we construct models in which inverse seesaw neutrino masses are generated at two loop level. These models also naturally have dark matter candidates. Although the recent data from Xenon100 put stringent constraint on the models, they can be consistent with data on neutrino masses, mixing, dark matter relic density and direct detection. These models also have some interesting experimental signatures for collider and flavor physics.

Abstract:
We study the possibility of generating tiny neutrino mass through a combination of type I and type II seesaw mechanism within the framework of an abelian extension of standard model. The model also provides a naturally stable dark matter candidate in terms of the lightest neutral component of a scalar doublet. We compute the relic abundance of such a dark matter candidate and also point out how the strength of type II seesaw term can affect the relic abundance of dark matter. Such a model which connects neutrino mass and dark matter abundance has the potential of being verified or ruled out in the ongoing neutrino, dark matter as well as accelerator experiments.

Abstract:
High energy accelerators may probe into dark matter and the seesaw neutrino mass scales if they are not much heavier than ~O(TeV). In the absence of supersymmetry, we extend a class of SO(10) models to predict well known cold dark matter candidates while achieving precision unification with experimentally testable proton lifetime. The most important prediction is a new radiative seesaw formula of Ma type accessible to accelerator tests while the essential small value of its quartic coupling also emerges naturally. This dominates over the high-scale seesaw contributions making a major impact on neutrino physics and dark matter, opening up high prospects as a theory of fermion masses.

Abstract:
We discuss how two birds---the little hierarchy problem of low-scale type-I seesaw models and the search for a viable dark matter candidate---are (proverbially) killed by one stone: a new inert scalar state