9,239 research outputs found
and decays within the Chiral Perturbation Theory
Decays and
are examined to the leading order
in momenta in the framework of Chiral Perturbation Theory. Predictions of the
Standard Model for the muon and electron differential energy spectra and
branching ratios of and are presented.Comment: 10 pages, 4 figures; v2: Introduction and Conclusion extended,
journal versio
Induced resonance makes light sterile neutrino Dark Matter cool
We describe two new generation mechanisms for Dark Matter composed of sterile
neutrinos with keV mass. The model contains a light scalar field
which coherently oscillates in the early Universe and modulates the Majorana
mass of the sterile neutrino. In a region of model parameter space, the
oscillations between active and sterile neutrinos are resonantly enhanced. This
mechanism allows us to produce sterile neutrino DM with small mixing angle with
active neutrinos, thus evading the X-ray constraints. At the same time the
spectrum of produced DM is much cooler, than in the case of ordinary
oscillations in plasma, opening a window of lower mass DM, which is otherwise
forbidden by structure formation considerations. In other regions of the model
parameter space, where the resonance does not appear, another mechanism can
operate: large field suppresses the active-sterile oscillations, but instead
sterile neutrinos are produced by the oscillating scalar field when the
effective fermion mass crosses zero. In this case DM component is cold, and
even 1 keV neutrino is consistent with the cosmic structure formation.Comment: 6 pages, 4 figures, PRD accepted versio
On decays of Z' into unparticle stuff
We study the decay of a Z' - boson into U -unparticle and a photon. The
extended Landau-Yang theorem is used. The clear photon signal would make the
decay Z' \rightarrow \gamma U as an additional contribution mode for study of
unparticle physics.Comment: 11 pages, 3 figures, paper accepted for publication by Advances in
High Energy Physics journa
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