KM3NeT: An underwater multi-km3 neutrino detector

The KM3NeT consortium is studying the main technological options for the construction of a research infrastructure in the Mediterranean Sea, hosting a neutrino telescope with an instrumented volume of several km3 and an integrated platform for earth and deep sea sciences. The telescope location will allow the survey of a large part of the Galactic plane, including the Galactic Centre, thus complementing the sky coverage of the IceCube telescope located at the South Pole. A telescope deployed in deep sea water is expected to have a very good angular resolution (of the order of 0.1° for neutrinos with 100 TeV energy), providing high sensitivity to point-like sources. The realization of this project will provide the scientific community with a powerful instrument to study and constrain the acceleration mechanisms of some astrophysical objects, including supernova remnants, active galactic nuclei, gamma-ray bursters. Neutrino telescopes can also investigate some of the most fundamental questions on HE physics beyond the standard model, including: the nature of dark matter through the indirect search for WIMPs, the study of subdominant effects on neutrino oscillations, including those possibly induced by the violation of the Lorentz invariance; the study of relic particles (magnetic monopoles, nuclearites) in cosmic radiation, the coincident neutrino emission with gravitational waves.This challenging project will require the installation of thousands of photon detectors with their related electronics and calibration systems several kilometers below sea level. This contribution presents an outline of the technological aspects of the project and a discussion of its main physics goals and expected performances, with a proposed preliminary timeline towards the completion of this instrument.