907 research outputs found
Constraints on secondary 10-100 EeV gamma ray flux in the minimal bottom-up model of Ultra High Energy Cosmic Rays
In a recently proposed model the cosmic rays spectrum at energies above EeV
can be fitted with a minimal number of unknown parameters assuming that the
extragalactic cosmic rays are only protons with a power law source spectrum.
Within this minimal model, after fitting the observed HiRes spectrum with four
parameters (proton injection spectrum power law index, maximum energy, minimum
distance to sources and evolution parameter) we compute the flux of ultra-high
energy photons due to photon-pion production and e+e- pair production by
protons for several radio background models and a range of average
extragalactic magnetic fields.Comment: Contribution to the 30th International Cosmic Ray Conference, Merida,
Mexico, July 2007, 4 pages, 4 figure
Contributions to the knowledge of larval development in Cyclops leuckarti Claus [Translation from: Natura, Milano 19, 89-96, 1928]
Taxonomic observations on the larval forms of Cyclops leuckarti are being discussed and compared with Cyclops oithonoides var. hyalina. Observations include Nauplius and Metanauplius stages. The author concludes that specific differences are recognisable even in the nauplius stages
Direct detection of neutralino dark mattter in non-standard cosmologies
We compute the neutralino direct detection rate in non-standard cosmological
scenarios where neutralinos account for the dark matter of the Universe.
Significant differences are found when such rates are compared with those
predicted by the standard cosmological model. For bino-like neutralinos, the
main feature is the presence of additional light (m_\chi\lesssim 40\gev) and
heavy (m_\chi\gtrsim 600\gev) neutralinos with detection rates within the
sensitivity of future dark matter experiments. For higgsino- and wino-like
neutralinos lighter than m_\chi \sim 1\tev, enhancements of more than two
orders of magnitude in the largest detection rates are observed. Thus, if dark
matter is made up of neutralinos, the prospects for their direct detection are
in general more promising than in the standard cosmology.Comment: 10 pages, 5 figure
Measuring the prompt atmospheric neutrino flux with down-going muons in neutrino telescopes
In the TeV energy region and above, the uncertainty in the level of prompt
atmospheric neutrinos would limit the search for diffuse astrophysical
neutrinos. We suggest that neutrino telescopes may provide an empirical
determination of the flux of prompt atmospheric electron and muon neutrinos by
measuring the flux of prompt down-going muons. Our suggestion is based on the
consideration that prompt neutrino and prompt muon fluxes at sea level are
almost identical.Comment: 4 pages, 3 figure
DAMA detection claim is still compatible with all other DM searches
We show that the annual modulation signal observed by DAMA can be reconciled
with all other negative results from dark matter searches with a conventional
halo model for particle masses around 5 to 9 GeV. We also show which particular
dark matter stream could produce the DAMA signal.Comment: Talk given at TAUP2005, Sept. 10-14 2005, Zaragoza (Spain). 3 pages,
4 figure
Ultra-High Energy Cosmic Rays and the GeV-TeV Diffuse Gamma-Ray Flux
Ultra-high energy cosmic ray protons accelerated in astrophysical objects
produce secondary electromagnetic cascades during propagation in the cosmic
microwave and infrared backgrounds. We show that such cascades can contribute
between ~1% and ~50% of the GeV-TeV diffuse photon flux measured by the EGRET
experiment. The GLAST satellite should have a good chance to discover this
flux.Comment: 4 pages, 5 figure
Super-Kamiokande 0.07 eV Neutrinos in Cosmology: Hot Dark Matter and the Highest Energy Cosmic Rays
Relic neutrinos with mass in the range indicated by Super-Kamiokande results
if neutrino masses are hierarchial (about 0.07 eV) are many times deemed too
light to be cosmologically relevant. Here we remark that these neutrinos may
significantly contribute to the dark matter of the Universe (with a large
lepton asymmetry ) and that their existence might be revealed by the
spectrum of ultra high energy cosmic rays (maybe even in the absence of a large
).Comment: Talk given at the ``4th International Symposium on Sources and
Detection of Dark Matter in the Universe", February 23-25, 2000, Marina del
Rey, CA (to appear in its proceedings) and at the ``Cosmic Genesis and
Fundamental Physics" workshop, October 28-30, 1999, Sonoma State University,
Santa Rosa, CA. (8 p. 1 fig.
Hints of Standard Model Higgs Boson at the LHC and Light Dark Matter Searches
The most recent results of searches at the LHC for the Higgs boson h have
turned up possible hints of such a particle with mass m_h about 125 GeV
consistent with standard model (SM) expectations. This has many potential
implications for the SM and beyond. We consider some of them in the contexts of
a simple Higgs-portal dark matter (DM) model, the SM plus a real gauge-singlet
scalar field D as the DM candidate, and a couple of its variations. In the
simplest model with one Higgs doublet and three or four generations of
fermions, for D mass m_D DD tends to have a
substantial branching ratio. If future LHC data confirm the preliminary Higgs
indications, m_D will have to exceed m_h/2. To keep the DM lighter than m_h/2,
one will need to extend the model and also satisfy constraints from DM direct
searches. The latter can be accommodated if the model provides sizable isospin
violation in the DM-nucleon interactions. We explore this in a
two-Higgs-doublet model combined with the scalar field D. This model can offer
a 125-GeV SM-like Higgs and a light DM candidate having isospin-violating
interactions with nucleons at roughly the required level, albeit with some
degree of fine-tuning.Comment: 17 pages, 4 figures, slightly revised, main conclusions unchanged,
references added, matches published versio
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