1,000 research outputs found
X-ray line signal from decaying axino warm dark matter
We consider axino warm dark matter in a supersymmetric axion model with
R-parity violation. In this scenario, axino with the mass m_\axino\simeq 7
keV can decay into photon and neutrino resulting in the X-ray line signal at
keV, which might be the origin of unidentified X-ray emissions from
galaxy clusters and Andromeda galaxy detected by the XMM-Newton X-ray
observatory.Comment: 8 pages, 2 figures, typos corrected, discussion and one more figure
added, the final journal versio
Searching for Axino-Like Particle at Fixed Target Experiments
We investigate the detectability of axino-like particle, which is defined as
a supersymmetric partner of axion-like particle and can be a good candidate for
dark matter in our Universe. Especially, we consider the fixed target
experiments to search for the light axino-like particle with a neutralino as
the next-to-lightest supersymmetric particle. We calculate the production and
decay rate of neutralinos and the consequent number of events (such as photons
and charged leptons) that are produced when the neutralinos decay to the
axino-like particles.Comment: 10 pages, 7 figures, Published in Physics of the Dark Univers
Dirac right-handed sneutrino dark matter and its signature in the gamma-ray lines
We show that a Dirac right-handed scalar neutrino can be weakly interacting
massive particle in the neutrinophilic Higgs model. When the additional Higgs
fields couple only to the leptonic sector through neutrino Yukawa couplings,
the right number of relic density of dark matter can be obtained from thermal
freeze-out of the dark matter annihilation into charged leptons and neutrinos.
At present, this annihilation is suppressed by the velocity of dark matter.
However one-loop annihilation cross section into can be larger
than that of the helicity suppressed annihilation into fermions, because
relevant coupling constants are different. Hence, gamma-ray line signal which
might have been observed in the Fermi-LAT is also able to be explained by its
annihilation.Comment: 11pages, final versio
Non-Gaussianity and gravitational wave background in curvaton with a double well potential
We study the density perturbation by a curvaton with a double well potential
and estimate the nonlinear parameters for non-Gaussianity and the amplitude of
gravitational wave background generated during inflation. The predicted
nonlinear parameters strongly depend on the size of a curvaton self-coupling
constant as well as the reheating temperature after inflation for a given
initial amplitude of the curvaton. The difference from usual massive
self-interacting curvaton is also emphasized.Comment: 23 pages, 6 figure
Modulated reheating by curvaton
There might be a light scalar field during inflation which is not responsible
for the accelerating inflationary expansion. Then, its quantum fluctuation is
stretched during inflation. This scalar field could be a curvaton, if it decays
at a late time. In addition, if the inflaton decay rate depends on the light
scalar field expectation value by interactions between them, density
perturbations could be generated by the quantum fluctuation of the light field
when the inflaton decays. This is modulated reheating mechanism. We study
curvature perturbation in models where a light scalar field does not only play
a role of curvaton but also induce modulated reheating at the inflaton decay.
We calculate the non-linearity parameters as well as the scalar spectral index
and the tensor-to-scalar ratio. We find that there is a parameter region where
non-linearity parameters are also significantly enhanced by the cancellation
between the modulated effect and the curvaton contribution. For the simple
quadratic potential model of both inflaton and curvaton, both tensor-to-scalar
ratio and nonlinearity parameters could be simultaneously large.Comment: 26 pages, 22 figure
The colonization pattern by resistant microorganisms in an adult intensive care unit (ICU)
published_or_final_versio
Light cold dark matter from non-thermal decay
We investigate the mass range and the corresponding free-streaming length
scale of dark matter produced non-thermally from decay of heavy objects which
can be either dominant or sub-dominant at the moment of decay. We show that the
resulting dark matter could be very light well below keV scale with a
free-streaming length satisfying the Lyman-{\alpha} constraints. We demonstrate
two explicit examples for such light cold dark matter.Comment: 8 pages, 4 figure
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