116 research outputs found
Reconciliation of CDM abundance and in a radiative seesaw model
We reexamine relic abundance of a singlet fermion as a CDM candidate, which
contributes to the neutrino mass generation through radiative seesaw mechanism.
We search solutions for Yukawa couplings and the mass spectrum of relevant
fields to explain neutrino oscillation data. For such solutions, we show that
an abundance of a lightest singlet fermion can be consistent with WMAP data
without conflicting with both bounds of and . This reconciliation does not need any modification of the original
radiative seesaw model other than by specifying flavor structure of Yukawa
couplings and taking account of coannihilation effects.Comment: 16 pages, 2 figures, accepted version for publication
Enhancement of the annihilation of dark matter in a radiative seesaw model
The radiative seesaw model with an inert doublet has been shown to be
attractive from a viewpoint of both neutrino masses and cold dark matter.
However, if we apply this model to the explanation of the positron excess in
the cosmic ray observed by PAMELA, a huge boost factor is required although it
can be automatically explained that no anti-proton excess has been observed
there. We consider an extension of the model to enhance the thermally averaged
annihilation cross section without changing the features of the model favored
by both the neutrino oscillation and the relic abundance of dark matter. It is
shown that the data of PAMELA and Fermi-LAT can be well explained in this
extended model. Constraints from gamma ray observations are also discussed.Comment: 28 pages, 5 figures, final version for publicatio
Neutrino masses and terms in a supersymmetric extra U(1) model
We propose a supersymmetric extra U(1) model, which can generate small
neutrino masses and necessary terms, simultaneously. Fields including
quarks and leptons are embedded in three s of in a different
way among generations. The model has an extra U(1) gauge symmetry at TeV
regions, which has discriminating features from other models studied
previously. Since a neutrino mass matrix induced in the model has a constrained
texture with limited parameters, it can give a prediction. If we impose
neutrino oscillation data to fix those parameters, a value of
can be determined. We also discuss several phenomenological features which are
discriminated from the ones of the MSSM.Comment: 27 pages, 2 figures, final version for publicatio
Dark matter in the supersymmetric radiative seesaw model with an anomalous U(1) symmetry
金沢大学理工研究域数物科学系The existence of an anomalous U(1) symmetry is shown to play a crucial role in the supersymmetric radiative seesaw model for neutrino masses. It explains the smallness of some couplings related to neutrino mass generation in a favorable way in addition to cause the hierarchical structure of Yukawa couplings of quarks and leptons. If it is spontaneously broken to a Z2 subgroup, this Z2 symmetry can make a lifetime of the lightest field with its odd parity extremely long. Thus, the model has an additional dark matter candidate other than the lightest neutralino, which appears in the R-parity conserved MSSM. We discuss the nature of dark matter by taking account of its relation to the neutrino mass generation and the lepton flavor violation. © 2011 Elsevier B.V
Observations of Sunspot Oscillations in G band and Ca II H line with Solar Optical Telescope on Hinode
Exploiting high-resolution observations made by the Solar Optical Telescope
onboard Hinode, we investigate the spatial distribution of power spectral
density of oscillatory signal in and around NOAA active region 10935. The
G-band data show that in the umbra the oscillatory power is suppressed in all
frequency ranges. On the other hand, in Ca II H intensity maps oscillations in
the umbra, so-called umbral flashes, are clearly seen with the power peaking
around 5.5 mHz. The Ca II H power distribution shows the enhanced elements with
the spatial scale of the umbral flashes over most of the umbra but there is a
region with suppressed power at the center of the umbra. The origin and
property of this node-like feature remain unexplained.Comment: 7 pages, 8 figures, accepted for publication in PASJ (Hinode Special
Issue
Reconciliation of CDM abundance and μ→eγ in a radiative seesaw model
金沢大学理工研究域数物科学系We reexamine relic abundance of a singlet fermion as a cold dark matter candidate, which contributes to the neutrino mass generation through radiative seesaw mechanism. We search solutions for Yukawa couplings and the mass spectrum of relevant fields to explain neutrino oscillation data. For such solutions, we show that an abundance of a lightest singlet fermion can be consistent with WMAP data without conflicting with both bounds of μ→eγ and τ→μγ. This reconciliation does not need any modification of the original radiative seesaw model other than by specifying flavor structure of Yukawa couplings and taking account of coannihilation effects. © 2009 The American Physical Society
Enhancement of the annihilation of dark matter in a radiative seesaw model
金沢大学理工研究域数物科学系The radiative seesaw model with an inert doublet has been shown to be attractive from a viewpoint of both neutrino masses and cold dark matter. However, if we apply this model to the explanation of the positron excess in the cosmic ray observed by PAMELA, a huge boost factor is required although it can be automatically explained that no antiproton excess has been observed there. We consider an extension of the model to enhance the thermally averaged annihilation cross section without changing the features of the model favored by both the neutrino oscillation and the relic abundance of dark matter. It is shown that the data of PAMELA and Fermi-LAT can be well explained in this extended model. Constraints from gamma ray observations are also discussed. © 2010 The American Physical Society
Initial Helioseismic Observations by Hinode/SOT
Results from initial helioseismic observations by Solar Optical Telescope
onboard Hinode are reported. It has been demonstrated that intensity
oscillation data from Broadband Filter Imager can be used for various
helioseismic analyses. The k-omega power spectra, as well as corresponding
time-distance cross-correlation function that promises high-resolution
time-distance analysis below 6-Mm travelling distance, were obtained for G-band
and CaII-H data. Subsurface supergranular patterns have been observed from our
first time-distance analysis. The results show that the solar oscillation
spectrum is extended to much higher frequencies and wavenumbers, and the
time-distance diagram is extended to much shorter travel distances and times
than they were observed before, thus revealing great potential for
high-resolution helioseismic observations from Hinode.Comment: 6 pages, accepted for publication in PAS
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