1,806 research outputs found
PAMELA and ATIC Anomalies in Decaying Gravitino Dark Matter Scenario
Motivated by the recent results from the PAMELA and ATIC, we study the
cosmic-ray electron and positron produced by the decay of gravitino dark
matter. We calculate the cosmic-ray electron and positron fluxes and discuss
implications to the PAMELA and ATIC data. In this paper, we will show that the
observed anomalous fluxes by the PAMELA and ATIC can be explained in such a
scenario. We will also discuss the synchrotron radiation flux from the Galactic
center in such a scenario.Comment: Prepared for the proceedings of Dark 2009:Seventh International
Heidelberg Conference on Dark Matter in Astro and Particle Physic
Gravitino Dark Matter with Weak-Scale Right-Handed Sneutrino
We consider cosmological implications of supersymmetric models with
right-handed (s)neutrinos where the neutrino masses are purely Dirac-type. We
pay particular attention to the case where gravitino is the lightest
superparticle while one of the right-handed sneutrinos is next-to-the-lightest
superparticle. We study constraints from big-bang nuleosynthesis and show that
the constraints could be relaxed compared to the case without right-handed
sneutrinos. As a result, the gravitino-dark-matter scenario becomes viable with
relatively large value of the gravitino mass. We also discuss constraints from
the structure formation; in our model, the free-streaming length of the
gravitino dark matter may be as long as O(1 Mpc), which is comparable to the
present observational upper bound on the scale of free-streaming.Comment: 18 pages, 6 figure
Wino Dark Matter and Future dSph Observations
We discuss the indirect detection of the wino dark matter utilizing gamma-ray
observations of dwarf spheroidal galaxies (dSphs). After carefully reviewing
current limits with particular attention to astrophysical uncertainties, we
show prospects of the wino mass limit in future gamma-ray observation by the
Fermi-LAT and the GAMMA-400 telescopes. We find that the improvement of the
so-called -factor of both the classical and the ultra-faint dSphs will play
a crucial role to cover whole mass range of the wino dark matter. For example,
with for both the classical and the ultra-faint
dSphs, whole wino dark matter mass range can be covered by 15 years and 10
years data at the Fermi-LAT and GAMMA-400 telescopes, respectively.Comment: 32 pages, 13 figure
High-Scale SUSY Breaking Models in light of the BICEP2 Result
The large value of the tensor-to-scalar ratio in the cosmic microwave
background radiation reported by the BICEP2 collaboration gives strong impact
on models of supersymmetry (SUSY). The large ratio indicates inflation with a
high-energy scale and thus a high reheating temperature in general, and various
SUSY models suffer from the serious gravitino and Polonyi problems. In this
article, we discuss a class of the high-scale SUSY breaking models which are
completely free from those problems. With especially focusing on the dark
matter relic abundance, we examine how the BICEP2 result narrows down the
parameter space of the models, assuming the simplest chaotic inflation model.
We find that the mass of the dark matter is predicted to be less than about 1
TeV thanks to the non-thermal production in the early universe through the
decay of abundant gravitinos produced after the reheating process. We also
discuss implications in some details to dark matter searches at collider and
indirect dark matter detection experiments.Comment: 17 pages, 6 figure
Indirect Probe of Electroweak-Interacting Particles at Future Lepton Colliders
Various types of electroweak-interacting particles, which have non-trivial
charges under the gauge symmetry,
appear in various extensions of the Standard Model. These particles are good
targets of future lepton colliders, such as the International Linear Collider
(ILC), the Compact LInear Collider (CLIC) and the Future Circular Collider of
electrons and positrons (FCC-ee). An advantage of the experiments is that, even
if their beam energies are below the threshold of the production of the new
particles, quantum effects of the particles can be detected through high
precision measurements. We estimate the capability of future lepton colliders
to probe electroweak-interacting particles through the quantum effects, with
particular focus on the wino, the Higgsino and the so-called minimal dark
matters, and found that a particle whose mass is greater than the beam energy
by 100-1000 GeV is detectable by measuring di-fermion production cross sections
with \% accuracy. In addition, with the use of the same analysis, we
also discuss the sensitivity of the future colliders to model independent
higher dimensional operators, and found that the cutoff scales corresponding to
the operators can be probed up to a few ten TeV
Heavy Fermion Bound States for Diphoton Excess at 750GeV Collider and Cosmological Constraints
A colored heavy particle with sufficiently small width may form
non-relativistic bound states when they are produced at the large hadron
collider\,(LHC), and they can annihilate into a diphoton final state. The
invariant mass of the diphoton would be around twice of the colored particle
mass. In this paper, we study if such bound state can be responsible for the
750 GeV diphoton excess reported by ATLAS and CMS. We found that the best-fit
signal cross section is obtained for the SU(2) singlet colored fermion
with . Having such an exotic hypercharge, the particle is expected to
decay through some higher dimensional operators, consistent with the small
width assumption. The decay of may involve a stable particle , if
both and are odd under some conserved symmetry. In that case,
the particle suffers from the constraints of jets + missing searches
by ATLAS and CMS at 8 TeV and 13 TeV. We found that such a scenario still
survives if the mass difference between and is above 30 GeV
for GeV. Even assuming pair annihilation of is small, the
relic density of is small enough if the mass difference between and
is smaller than 40 GeV
Locally Conformal Almost Cosymplectic Manifolds Endowed with a Skew-Symmetric Killing Vector Field
We study a locally conformal almost cosymplectic manifold M which carries a horizontal skew-symmetric Killing vector field X. Such X denes a relative conformal cosymplectic transformation of the conformal cosymplectic 2-form Ω of M and the square of its length is both an isoparametric function and an eigenfunction of the Laplacian. Math. Subject Classification 2000: 53D15, 53C15. Keywords: Locally conformal almost cosymplectic manifolds, skew-symmetric Killing vector feld, infinitesimal concircular transformation, relative conformal cosymplectic transformation
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