2,588 research outputs found
Spectral analysis of the high-energy IceCube neutrinos
A full energy and flavor-dependent analysis of the three-year high-energy
IceCube neutrino events is presented. By means of multidimensional fits, we
derive the current preferred values of the high-energy neutrino flavor ratios,
the normalization and spectral index of the astrophysical fluxes, and the
expected atmospheric background events, including a prompt component. A crucial
assumption resides on the choice of the energy interval used for the analyses,
which significantly biases the results. When restricting ourselves to the ~30
TeV - 3 PeV energy range, which contains all the observed IceCube events, we
find that the inclusion of the spectral information improves the fit to the
canonical flavor composition at Earth, (1:1:1), with respect to a single-energy
bin analysis. Increasing both the minimum and the maximum deposited energies
has dramatic effects on the reconstructed flavor ratios as well as on the
spectral index. Imposing a higher threshold of 60 TeV yields a slightly harder
spectrum by allowing a larger muon neutrino component, since above this energy
most atmospheric tracklike events are effectively removed. Extending the
high-energy cutoff to fully cover the Glashow resonance region leads to a
softer spectrum and a preference for tau neutrino dominance, as none of the
expected electron antineutrino induced showers have been observed so far. The
lack of showers at energies above 2 PeV may point to a broken power-law
neutrino spectrum. Future data may confirm or falsify whether or not the
recently discovered high-energy neutrino fluxes and the long-standing detected
cosmic rays have a common origin.Comment: 33 pages, 13 figures. v3: one extra figure (fig. 13), some references
updated and some formulae moved to the Appendix. It matches version published
in PR
Are small neutrino masses unveiling the missing mass problem of the Universe?
We present a scenario in which a remarkably simple relation linking dark
matter properties and neutrino masses naturally emerges. This framework points
towards a low energy theory where the neutrino mass originates from the
existence of a light scalar dark matter particle in the MeV mass range. A very
surprising aspect of this scenario is that the required MeV dark matter is one
of the favoured candidates to explain the mysterious emission of 511 keV
photons in the centre of our galaxy. A possible interpretation of these
findings is that dark matter is the stepping stone of a theory beyond the
standard model instead of being an embarrassing relic whose energy density must
be accounted for in any successful model building.Comment: 4pages, 2 figures. Two paragraphs have been added. One for the
complex case; the other one for the UV completio
Design, expression, and characterization of an asymmetric bispecific antibody fused to a scFv shuttle for brain uptake
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