Measuring the 13-mixing angle and the CP phase with neutrino telescopes

The observed excess of high-energy cosmic rays from the Galactic plane in the energy range \sim 10^18 eV may be naturally explained by neutron primaries generated in the photo-dissociation of heavy nuclei. In this scenario, neutrons with lower energy decay before reaching the Earth and produce a detectable flux in a 1 km^3 neutrino telescope. The initial flavor composition of these neutrinos, \phi(\bar\nu_e):\phi(\bar\nu_\mu):\phi(\bar\nu_\tau)=1:0:0, offers the opportunity to perform a combined \bar\nu_\mu/\bar\nu_\tau appearance and \bar\nu_e disappearance experiment. The observable ratio \phi(\bar\nu_\mu)/\phi(\bar\nu_e+\bar\nu_\tau) of fluxes arriving on Earth depends appreciably on the 13-mixing angle \theta_13 and the leptonic CP phase \delta_CP, opening thus a new experimental avenue to measure these two quantities.Comment: 4 pages, 2 eps figures. Enlarged discussion, references added. Matches version to appear in PR

Cherenkov Telescope Array: The next-generation ground-based gamma-ray observatory

High energy gamma-ray astronomy is a newly emerging and very successful branch of astronomy and astrophysics. Exciting results have been obtained by the current generation Cherenkov telescope systems such as H.E.S.S., MAGIC, VERITAS and CANGAROO. The H.E.S.S. survey of the galactic plane has revealed a large number of sources and addresses issues such as the question about the origin of cosmic rays. The detection of very high energy emission from extragalactic sources at large distances has provided insights in the star formation during the history of the universe and in the understanding of active galactic nuclei. The development of the very large Cherenkov telescope array system (CTA) with a sensitivity about an order of magnitude better than current instruments and significantly improved sensitivity is under intense discussion. This observatory will reveal an order of magnitude more sources and due to its higher sensitivity and angular resolution it will be able to detect new classes of objects and phenomena that have not been visible until now. A combination of different telescope types will provide the sensitivity needed in different energy ranges.Comment: 4 pages, 3 figures, to appear in the proceedings of the 30th International Cosmic Ray Conference, Merida, July 200

The Galactic magnetic field as spectrograph for ultra-high energy cosmic rays

We study the influence of the regular component of the Galactic magnetic field (GMF) on the arrival directions of ultra-high energy cosmic rays (UHECRs). We find that, if the angular resolution of current experiments has to be fully exploited, deflections in the GMF cannot be neglected even for E=10^20 eV protons, especially for trajectories along the Galactic plane or crossing the Galactic center region. On the other hand, the GMF could be used as a spectrograph to discriminate among different source models and/or primaries of UHECRs, if its structure would be known with sufficient precision. We compare several GMF models introduced in the literature and discuss for the example of the AGASA data set how the significance of small-scale clustering or correlations with given astrophysical sources are affected by the GMF. We point out that the non-uniform exposure to the extragalactic sky induced by the GMF should be taken into account estimating the significance of potential (auto-)correlation signals.Comment: 11 pages, 8 figures; minor corrections, enlarged discussion, contains an extended review on Galactic magnetic field compared to published version, to appear in Astroparticle Physic