393 research outputs found
Getting the most from NOvA and T2K
The determination of the ordering of the neutrino masses (the hierarchy) is
probably a crucial prerequisite to understand the origin of lepton masses and
mixings and to establish their relationship to the analogous properties in the
quark sector. In this talk, we follow an alternative strategy to the usual
neutrino--antineutrino comparison: we exploit the combination of the
neutrino-only data from the NOvA and the T2K experiments by performing these
two off-axis experiments at different distances but at the same ,
being the mean neutrino energy and the baseline. This would require a minor
adjustment to the proposed off-axis angle for one or both of the proposed
experiments.Comment: 7 pages, 2 figures, Proccedings of Neutrino 2006 Conference, Santa
Fe, New Mexico, June 13-19, 200
Physics Potential of the Fermilab NuMI beamline
We explore the physics potential of the NuMI beamline with a detector located
10 km off-axis at a distant site (810 km). We study the sensitivity to and to the CP-violating parameter as well as the
determination of the neutrino mass hierarchy by exploiting the and appearance channels. The results are
illustrated for three different experimental setups to quantify the benefits of
increased detector sizes, proton luminosities and detection
efficiencies.Comment: 23 pages, 12 figure
High Energy Neutrinos from Novae in Symbiotic Binaries: The Case of V407 Cygni
Detection of high-energy (~> 100 MeV) gamma rays by the Fermi Large Area
Telescope (LAT) from a nova in the symbiotic binary system V407 Cygni has
opened possibility of high-energy neutrino detection from this type of sources.
Thermonuclear explosion on the white dwarf surface sets off a nova shell in
motion that expands and slows down in a dense surrounding medium provided by
the red giant companion. Particles are accelerated in the shocks of the shell,
and interact with surrounding medium to produce observed gamma rays. We show
that proton-proton interaction, which is most likely responsible for producing
gamma rays via neutral pion decay, produces ~> 0.1 GeV neutrinos that can be
detected by the current and future experiments at ~> 10 GeV.Comment: 5 pages, 2 figures, expanded discussion on detectability, accepted
for publication in Phys. Rev.
NOvA and T2K: The race for the neutrino mass hierarchy
The determination of the ordering of the neutrino masses (the hierarchy) is
probably a crucial prerequisite to understand the origin of lepton masses and
mixings and to establish their relationship to the analogous properties in the
quark sector. Here, we follow an alternative strategy to the usual
neutrino--antineutrino comparison in long baseline neutrino oscillation
experiments: we exploit the combination of the neutrino-only data from the NOvA
and the T2K experiments by performing these two off-axis experiments at
different distances but at the same , where is the mean neutrino
energy and is the baseline. This would require a minor adjustment to the
proposed off-axis angle for one or both of the proposed experiments.Comment: 19 pages, 7 figures, LaTE
Ultrahigh-energy neutrino flux as a probe of large extra-dimensions
A suppression in the spectrum of ultrahigh-energy (UHE, >= 10^{18} eV)
neutrinos will be present in extra-dimensional scenarios, due to enhanced
neutrino-antineutrino annihilation processes with the supernova relic
neutrinos. In the n>4 scenario, being n the number of extra dimensions,
neutrinos can not be responsible for the highest energy events observed in the
UHE cosmic ray spectrum. A direct implication of these extra-dimensional
interactions would be the absence of UHE neutrinos in ongoing and future
neutrino telescopes.Comment: JCAP accepted version. Included 5, 6 and 7 extra-dimensional cases,
and 2 new figures. The conclusion remains unchanged that UHE neutrino flux
would be suppressed in large extra-dimensional model
Oscillation effects on high-energy neutrino fluxes from astrophysical hidden sources
High-energy neutrinos are expected to be produced in a vareity of
astrophysical sources as well as in optically thick hidden sources. We explore
the matter-induced oscillation effects on emitted neutrino fluxes of three
different flavors from the latter class. We use the ratio of electron and tau
induced showers to muon tracks, in upcoming neutrino telescopes, as the
principal observable in our analysis. This ratio depends on the neutrino
energy, density profile of the sources and on the oscillation parameters. The
largely unknown flux normalization drops out of our calculation and only
affects the statistics. For the current knowledge of the oscillation parameters
we find that the matter-induced effects are non-negligible and the enhancement
of the ratio from its vacuum value takes place in an energy range where the
neutrino telescopes are the most sensitive. Quantifying the effect would be
useful to learn about the astrophysics of the sources as well as the
oscillation parameters. If the neutrino telescopes mostly detect diffuse
neutrinos without identifying their sources, then any deviation of the measured
flux ratios from the vacuum expectation values would be most naturally
explained by a large population of hidden sources for which matter-induced
neutrino oscillation effects are important.Comment: Phys.Rev.D accepted version. 12 pages, 10 figures. Results unchanged,
added references, minor changes and text re-arrangement
Can interacting dark energy solve the tension?
The answer is Yes! We indeed find that interacting dark energy can alleviate
the current tension on the value of the Hubble constant between the
Cosmic Microwave Background anisotropies constraints obtained from the Planck
satellite and the recent direct measurements reported by Riess et al. 2016. The
combination of these two datasets points towards an evidence for a non-zero
dark matter-dark energy coupling at more than two standard deviations,
with at CL. However the tension is
better solved when the equation of state of the interacting dark energy
component is allowed to freely vary, with a phantom-like equation of state
(at CL), ruling out the pure cosmological constant
case, , again at more than two standard deviations. When Planck data are
combined with external datasets, as BAO, JLA Supernovae Ia luminosity
distances, cosmic shear or lensing data, we find good consistency with the
cosmological constant scenario and no compelling evidence for a dark
matter-dark energy coupling.Comment: 10 pages, 6 figure
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
Phenomenological approaches of inflation and their equivalence
In this work, we analyze two possible alternative and model-independent
approaches to describe the inflationary period. The first one assumes a general
equation of state during inflation due to Mukhanov, while the second one is
based on the slow-roll hierarchy suggested by Hoffman and Turner. We find that,
remarkably, the two approaches are equivalent from the observational viewpoint,
as they single out the same areas in the parameter space, and agree with the
inflationary attractors where successful inflation occurs. Rephrased in terms
of the familiar picture of a slowly rolling, canonically normalized scalar
field, the resulting inflaton excursions in these two approaches are almost
identical. Furthermore, once the Galactic dust polarization data from Planck
are included in the numerical fits, inflaton excursions can safely take
sub-Planckian values.Comment: Revtex, 8 pages, 4 figures. References updated. Matches published
version in PR
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