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Particle astrophysics is a new multidisciplinary field of research (where Elementary Particle Physics, Astronomy & Astrophysics and Cosmology converge) that deals with the study of particles coming from the Universe. Until the early 1950s, cosmic rays - charged high-energy particles from outer space – were the main source of information for advances in knowledge about the nature of matter in the Universe. Then, particle accelerators opened the path to tremendous progress, providing high-energy particle beams to investigate the structure of matter. However, today we are going back to study ultrahigh energy cosmic rays because new kinds of detectors allow us to detect cosmic rays with energies far beyond the limits of accelerators. Particle astrophysics employs new detection methods to observe a wide range of cosmic particles such as, neutrinos, gamma rays and very high-energy cosmic rays. This has led to the design of new types of infrastructure:
- Underground Laboratories shielding the experiments from the cosmic muon background.
- "Observatories” or “telescopes” or “antennas” on earth whose optimal size is generally large due to the weakness (for gravitational waves) or the scarcity (for very high energy gamma rays, neutrinos or very high energy cosmic rays) of the signals which are to be detected.
- Satellite observatories of high energy gamma rays, cosmic rays or gravitational waves.
By comparing observations through different windows and at various energies, we aim to learn more about high-energy cosmic phenomena in the Universe and the violent processes that give rise to them. A series of astrophysical objects demand an interdisciplinary, multi-wavelength and multi-messenger approach for their comprehension. Furthermore, astrophysical sites of violent phenomena can be used as a laboratory to test the structure of the fundamental laws of particle physics and gravitation.
- Antarctica-based Ice Cube and Ice Top Neutrino Observatory (Gaisser, Seckel, Clem, Evenson, Stanev).
- Antarctica-based ANITA radio telescope to detect ultra-high energy cosmic-ray neutrinos from a scientific balloon flying over the continent of Antarctica - ANITA is the first NASA observatory for neutrinos of any kind (Evenson, Seckel, Clem).
- Arizona-based VERITAS (Very Energetic Radiation Imaging Telescope Array System) detector for gamma-ray astronomy in the GeV - TeV energy range (Holder).
- AGIS is a next-generation ground-based gamma-ray observatory currently in the design and development phase. The goal is to improve the sensitivity over current instruments by an order of magnitude, which will likely be achieved by using a large array of telescopes to cover ~1km2 on the ground (Holder).