Acoustic Cosmic Ray Neutrino Experiment

The Universe's most energetic messengers...

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Cosmic rays with kinetic energies in excess of a Joule (10²¹eV) have already been observed by experiments such as AUGER. Detectors on the ground register the shower of particles and radiation that result from the collision of cosmic rays with the Earth’s atmosphere. Some of these cosmic rays never make it to the Earth because they interact with the Cosmic Microwave Background (CMB) radiation. Interactions between cosmic rays and the CMB can produce a different type of cosmic messenger called the neutrino. Furthermore the astrophysical particle-accelerator, or decaying exotic matter, that produces ultra high energy (UHE) cosmic rays could also produce neutrinos directly. Neutrinos interact weakly with matter and more often than not pass through the Earth without undergoing a collision. However, once in a while a UHE neutrino does interact, in which case much of its energy goes into heating the small volume of material surrounding the point of impact. This results in an almost-instantaneous temperature increase which can generate an acoustic pulse with a characteristic bipolar shape. This is illustrated in a short slide-show and is the principle behind the ACORNE experiment.

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