366 research outputs found

    Getting the most from NOvA and T2K

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    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 /L/L, being the mean neutrino energy and LL 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

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    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 sin22θ13\sin^2 2 \theta_{13} and to the CP-violating parameter sinδ\sin \delta as well as the determination of the neutrino mass hierarchy by exploiting the νμνe\nu_\mu \to \nu_e and νˉμνˉe\bar{\nu}_\mu \to \bar{\nu}_e appearance channels. The results are illustrated for three different experimental setups to quantify the benefits of increased detector sizes, proton luminosities and νe\nu_e detection efficiencies.Comment: 23 pages, 12 figure

    High Energy Neutrinos from Novae in Symbiotic Binaries: The Case of V407 Cygni

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    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

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    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 /L/L, where is the mean neutrino energy and LL 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

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    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

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    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 H0H_0 tension?

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    The answer is Yes! We indeed find that interacting dark energy can alleviate the current tension on the value of the Hubble constant H0H_0 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 ξ\xi at more than two standard deviations, with ξ=0.260.12+0.16\xi=-0.26_{-0.12}^{+0.16} at 95%95\% CL. However the H0H_0 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 w=1.184±0.064w=-1.184\pm0.064 (at 68%68 \% CL), ruling out the pure cosmological constant case, w=1w=-1, 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

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    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

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    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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