The Astroparticle Physics Group
Astroparticle physics (sometimes called particle astrophysics) is an emergent field of research on the border between particle physics, astrophysics and cosmology. The theoretical branch of this field explores issues relating to the evolution of the cosmos, gravity, dark matter and dark energy, connecting the domain of particle physics with astrophysics and cosmology. The experimental programs develop frontline detectors and study various forms of “messengers” reaching us from the outer space – cosmic rays, gamma rays, gravitational waves and neutrinos – to address questions relating to the origin of the ultra-high energy cosmic rays, the processes driving the energy output of some of the most luminous objects in the Universe (e.g. the vicinity of a super-massive black hole (active galactic nuclei), neutron star mergers, gamma ray bursts or super nova explosions), the nature of dark matter, the fundamental properties of neutrinos and aspects of physics beyond the Standard Model, among others. Multi-messenger astronomy is a relatively new development where (simultaneous) information from several types of messengers is correlated to gain additional insights.
The IceCube Neutrino Observatory
IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world's largest neutrino detector, encompassing a cubic kilometer of ice.
Radio detection of high-energy neutrinos
To measure neutrinos at the highest energies (beyond 1016 eV) even the huge optical IceCube detector becomes too small. The only cost-efficient way to measure these UHE neutrinos is via a sparse array of radio antenna stations installed in the Antarctic or Arctic ice: A neutrino interaction in the ice generates a few-nanoseconds long radio flash that can be detected from kilometer-long distances. We are involved in the ARIANNA project with detector stations on the Ross Ice Shelf and at the South Pole as well as the RNO-G project in Greenland. Our group activities range from a detailed simulation of radio signals from neutrinos, over data analysis to hardware development. One of our flagship projects are the development of the NuRadioMC simulation code is the development of a wind generator that survives the extreme weather conditions of the South Pole.
Hyper-K, currently under construction in Japan, consists of a water-filled cylindrical detector with a total (fiducial) volume of 258 (187) kilotonnes. When Hyper-K starts taking data in 2027 it will be a powerful neutrino telescope, with a physics program that includes a search for CP violation, solar neutrino studies, precision measurements of the diffuse supernova neutrino background, and the potential to measure a burst of neutrinos from a nearby supernova.