Astro-Particle Physics revolves around phenomena that involve (astro)physics under the most extreme conditions. Cosmic explosions and black holes with masses a billion times greater than the mass of the Sun, accelerate particles to velocities close to the speed of light. The produced high-energy particles may be detected on Earth and consequently can provide us insight in the physical processes underlying these cataclysmic events. As such, this field of research combines the insights of Astrophysics, Particle Physics and Cosmology. The research of the astro-particle physics group is centered around IceCube, the world's largest neutrino observatory at the South Pole. With the detector completed in December 2010, the data acquisition is now in full progress covering energies in the GeV-PeV range. In 2013 IceCube discovered a flux of very energetic cosmic neutrinos, which opened a whole new window on the universe: astrophysical and cosmological observations are now possible using neutrinos, revealing parts of the Universe not accessible by other messengers. As such, this research field is poised to yield unexpected discoveries. Apart from a search for high-energy (TeV-PeV) neutrinos from point sources and transient events, which would provide insight in the sources of the most energetic cosmic rays, the study of cosmic neutrinos would also allow to investigate neutrino properties.
IceCube's DeepCore component enables the detection of neutrinos as low as several GeV. Concerning the search for indirect cosmic Dark Matter signals this yields an increased sensitivity for lower particle masses and as such provides a complementary means w.r.t. the LHC experiments to search for related new physics phenomena.
A combination of IceCube dark matter candidates and LHC new physics (e.g. SUSY) observations could provide evidence that indeed these new particles are related to Dark Matter.
Using the outer IceCube sensors as an active veto, a clean environment is obtained to observe neutrinos over the full sky. This allows investigation of Galactic objects, including the Galactic Center and the black hole within it.
Furthermore, using a special data-taking mode and a dedicated analysis for GeV neutrinos our group is also searching for neutrinos related to solar flares and gravitational wave events.
At higher energies (i.e. EeV scale) our focus is on the detection of GZK neutrinos produced in cosmic ray interactions with the cosmic microwave background photons. These neutrinos would indicate that the cosmic ray flux drop around 100 EeV, as detected by Auger, is indeed due to this GZK effect. The flux of these GZK neutrinos will also uniquely provide insight in the composition of the most energetic cosmic rays. The very low flux at GZK-scale energies calls for extensions of the current detector and even new detection techniques. In view of this our group is involved in both the feasibility studies of the so-called IceCube-Gen2 high-energy upgrade as well as in the development of radio detection techniques for extremely high-energy neutrinos. The latter allows a detector area expansion of about two orders of magnitude, needed to obtain sufficient event statistics with this unique neutrino observatory.