IceCube detector spots highest-energy neutrinos ever

Ars Technica : Two neutrino-induced events with energy greater than 1 PeV have been reported by researchers at the IceCube Neutrino Observatory located at the South Pole. The observation is significant because it is likely the neutrinos originated in some high-energy event distant from Earth. Trillions of neutrinos, which emanate from a number of sources such as nuclear reactions in the Sun, pass through Earth every second. But they are extremely difficult to detect because they almost never interact with normal matter. Embedded in Antarctic ice, IceCube’s strings of photodetectors watch for the telltale emission of Cherenkov radiation when a neutrino passing through happens to collide with an atom in the ice. Most of the high-energy neutrinos detected by IceCube have come from cosmic rays colliding with atoms in Earth’s atmosphere. Because of the extremely high energy of the newly detected neutrinos, however, researchers believe they may be the first indication of an astrophysical high-energy neutrino fluxâmdash;an extremely energetic event that occurs far out in the universe. Longer sampling times and more data will be required to verify that finding.