The ORCA Option for KM3NeT
  It has recently been suggested that the neutrino mass hierarchy can be experimentally determined from the oscillation pattern of atmospheric neutrinos passing through the Earth by measuring the two-dimensional arrival pattern of neutrinos in energy and zenith angle, in the energy regime of about 3-20 GeV. ORCA (Oscillation Research with Cosmics in the Abyss) is a study addressing the feasibility of such a measurement employing the deep-sea neutrino telescope technology developed for the KM3NeT project. In the following, the underlying physics and resulting experimental signatures will be discussed and some aspects of the ongoing simulation studies presented. A preliminary sensitivity estimate derived from a simplified study strongly indicates that an exposure of at least 20 Mton-years will be required to arrive at conclusive results. 
Ulrich F. Katz (for the KM3NeT Collaboration)
astro-ph.IM hep-ex hep-ph