Light Sterile Neutrino in the Minimal Extended Seesaw

Physics Letters B (Impact Factor: 6.02). 10/2011; DOI: 10.1016/j.physletb.2012.06.074
Source: arXiv

ABSTRACT Motivated by the recent observations on sterile neutrinos, we present a
minimal extension of the canonical type-I seesaw by adding one extra singlet
fermion. After the decoupling of right-handed neutrinos, an eV-scale mass
eigenstate is obtained without the need of artificially inserting tiny mass
scales or Yukawa couplings for sterile neutrinos. In particular, the
active-sterile mixing is predicted to be of the order of 0.1. Moreover, we show
a concrete flavor A_4 model, in which the required structures of the minimal
extended seesaw are realized. We also comment on the feasibility of
accommodating a keV sterile neutrino as an attractive candidate for warm dark

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    ABSTRACT: Earlier studies of the influence of Dark Matter keV sterile neutrinos on neutrino-less double beta decay concluded that there is no significant modification of the decay rate. These studies have focused only on a mass of the keV sterile neutrino above 2 and 4 keV, respectively, as motivated by certain production mechanisms. On the other hand, alternative production mechanisms have been proposed, which relax the lower limit for the mass, and new experimental/observational data is available, too. For this reason, an updated study is timely and worthwhile. We focus on the most recent data, i.e., the newest Chandra and XMM-Newton observational bounds on the X-ray line originating from radiative keV sterile neutrino decay, as well as the new measurement of the previously unknown leptonic mixing angle $\theta_{13}$ by the Daya Bay, RENO, and Double Chooz experiments. We find that, while the previous works had been too short-sighted, the new observational bounds do indeed render any influences of keV sterile neutrinos on neutrino-less double beta decay small. This conclusion even holds in case not all the Dark Matter is made up of keV sterile neutrinos. The bounds are so powerful that they strongly constrain form-dominant neutrino mixing, which is of interest for models of keV sterile neutrinos.
    Physical Review D 02/2013; · 4.86 Impact Factor
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    ABSTRACT: We review the model building aspects for keV sterile neutrinos as Dark Matter candidates. After giving a brief discussion of some cosmological and astrophysical aspects, we first discuss the currently known neutrino data and observables. We then explain the purpose and goal of neutrino model building, and review some generic methods used. Afterwards certain aspects specific for keV neutrino model building are discussed, before reviewing the bulk of models in the literature. We try to keep the discussion on a pedagogical level, while nevertheless pointing out some finer details where necessary and useful. Ideally, this review should enable a grad student or an interested colleague from cosmology or astrophysics with some prior experience to start working on the field.
    International Journal of Modern Physics D 02/2013; · 1.42 Impact Factor
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    ABSTRACT: We propose a new production mechanism for keV sterile neutrino Dark Matter. In our setting, we assume the existence of a scalar singlet particle which never entered thermal equilibrium in the early Universe, since it only couples to the Standard Model fields by a really small Higgs portal interaction. For suitable values of this coupling, the scalar can undergo the so-called freeze-in process, and in this way be efficiently produced in the early Universe. These scalars can then decay into keV sterile neutrinos and produce the correct Dark Matter abundance. While similar settings in which the scalar does enter thermal equilibrium and then freezes out have been studied previously, the mechanism proposed here is new and represents a versatile extension of the known case. We perform a detailed numerical calculation of the DM production using a set of coupled Boltzmann equations, and we illustrate the successful regions in the parameter space. Our production mechanism notably can even work in models where active-sterile mixing is completely absent.
    Journal of Cosmology and Astroparticle Physics 06/2013; · 5.88 Impact Factor


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